The Black Art of GPU computing ! Help.

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RWremote
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Posts: 10
Joined: Wed Jul 27, 2011 1:00 am

The Black Art of GPU computing ! Help.

Post by RWremote »

Hi Guys.

I'm looking for a bit (lot) of advice with regard to number crunching with GPU's.

Never been down this road before so I've got a lot of questions, some I'm sure are going to seem really trivial, but when you don't know your ass from your elbow . . .
I'm not after anything that'll get me rocket powered, this is just a foray into GPU computing to see if I actually get any increase in my BOINC RAC.

I currently have a bunch of computers (three, all XP Pro) crunching the following projects :-
Quantum Monte-Carlo, Einstein, Milky-way and Primegrid,
Reading through various Forum posts, it would appear that the Milky-way project has the highest bar and requires a GPU supporting Double Precision arithmetic.

So, faffing around and taking all the money out of the piggy bank (£150.00) I've come up with the following card(s) :-

NVIDIA
1 - NVIDIA GeForce GT430 1024MB (~£48 )
2 - GeForce GTX 550 Ti 1024MB (~£99 !!!)

(AMD) ATI
1-VTX3D Radeon HD 4850 (~£75)
2-ATI Radeon HD 4830 (~$65)

My lowest Spec Machine (is pretty low) . . . . . . 2.13 gigahertz Intel Core 2 Duo/ 2GB RAM . . .  is this enough to keep a GPU fed with whatever it needs to be fed with ??

I think the NVIDIA card [GT430 1024MB] would be my choice, purely because the AMD site had the following for the Radeon Cards
"450 Watt or greater power supply with 75 Watt 6-pin PCI Express® power connector recommended . . . . .
(550 Watt and two 6-pin connectors for ATI CrossFireX™ technology in dual mode  . . . . . "

The AMD cards only have HDMI output and my screens are all VGA :( . . . . .
The NVIDIA presumably slots straight in the PCIe x16 slot and that's it ?

Now the silly stuff . . . .
IF the above is OK and I can install these cards, is it just plug and play and the BOINC agent will detect the card and use it ?
Or is this where the fun starts and I have to download some (CUDA ??) stuff and set it up ?
All my Boinc Clients are 6.10.60 - is this recent enough ?

Phew, if you've got to the end of this, thanks for reading, and treat yourself to glass of some strong cheer for the new year  !  :occasion5:

Cheers now
Zydor
Posts: 437
Joined: Mon Nov 01, 2010 12:00 am

Re: The Black Art of GPU computing ! Help.

Post by Zydor »

I'm looking for a bit (lot) of advice with regard to number crunching with GPU's.

Never been down this road before so I've got a lot of questions, some I'm sure are going to seem really trivial, but when you don't know your ass from your elbow . . .
I'm not after anything that'll get me rocket powered, this is just a foray into GPU computing to see if I actually get any increase in my BOINC RAC.
You will get an increase if you go GPU crunching - no shadow of a doubt, just a case of seeing where the runes fall after thinking through where to start.

First off .... with GPUs, the long route is always the shortest route. ie: don't be in a hurry to get going, get it right first time, and you'll avoid disappointment and likely added expense.

Second, be crystal clear on why you want to do this. Is it for the science or the credits, either are just as valid, there's no mythical kudos attached to either road. When you are clear on that, choose the Projects you want to support that meet your aims. Different cards for different projects at times, forget that for now, just choose the preferred projects whether its because of the science or high pay credits  - both don't happen in one project :)

Third, when clear on that, sit back and choose a short list of projects as candidates - say 4 or 5 of them.  From that you will get an idea of whether or not AMD or NVidia is the way to go and still give one or two back up projects in case the primary runs dry. Then you'll know which make to focus on.

Think through those three things first and come back with answers or related questions, its real important to get this bit right. Card discussion comes later, lets find out first what you are crunching.

IF the above is OK and I can install these cards, is it just plug and play and the BOINC agent will detect the card and use it ?
Basically yes
Or is this where the fun starts and I have to download some (CUDA ??) stuff and set it up ?
The selected Projects lead you by the nose and auto-install what you need.  There are other ways or doing it, but learn to walk before you run, let the Project software kick you off.
All my Boinc Clients are 6.10.60 - is this recent enough ?
No - change to 6.12.43, the 6.12.XX series had a lot of work put into it compared to 6.10.XX in the realms of GPU, change to that anytime as discussion proceeds to save time later.

I know much is missing on my post at present, but get the basics right first, then we can discuss merits of AMD and NVidia & their card offerings. As a broad proposition - for the card ranges you will get into - there's an old saying "AMD do the hardware, NVidia does the software". A broad generalisation that held true in the last few years - albeit I suspect its about to change with the new AMD 7XXX architecture.

AMD are on the cusp of releasing new cards, the first of a new genre, and they are fast .... careful thought will be needed as to waiting for the lower range 7XXX AMD cards if you go AMD, as the 7XXX cards are massively faster than previous generations, so do not assume 4XXX or 5XXX cards. We can have a detailed discussion on that once we are clear what projects you want, and there  whether or not its AMD or NVidia.

The hardware you have (cpu etc) will drive the level of card you can get with your proffered budget, no worries there. 2Ghz on up will drive a card - just be wary about laptops, broadly speaking with the budget you have, laptop & gpu not happening.  As a general principle, with your budget invest it in one Card, don't spread it across three cards on three machines. Three low end cards in three machines will cost high maintenance to run compared to one card in one machine.  Pick the best machine, and put in there the best card you can afford - we'll think through hardware needs like processor, PSU, etc etc later, for now think through which machine to put the card in.

Come back with the motivations, machine spec of the preferred machine and project list, and we can get going on the detail.

Regards
Zy
RWremote
UBT Contributor
Posts: 10
Joined: Wed Jul 27, 2011 1:00 am

Post by RWremote »

What a first class reply Zy, thank you very much, incredibly helpful.

Projects
My projects are (not in any order).
Einstein, Milky-Way, PrimeGrid & QMC. I do it for the science not the credit.
I'm not seeking new life forms, just trying to understand the universe around us, trying to understand the quantum chemistry of what makes us what we are and trying to make sense of it all.
The reason I'm crunching PrimeGrid is, I've always been fascinated by what mathematics can teach and help us to explore science. I'm also hoping that indirectly PrimeGrid will be be able to help the Astro physicists and Quantum engineers in their dealing with their own projects and experiments.
Looking at QMC it would appear that there is no GPU support apps for this project as yet, although they are working on them.
Ideally I would like to use GPU's to number crunch on Einstein, MW & PreimeGrid, but I'm obviously going to have to work on this.
So, if it has to be an order it would be
Milky-Way
Einstein
PrimeGrid.

PC's
Have three desktop Pc's that run these four projects. (They each have 25% share).
All PC's are desktops Midi's, have 2 Hard drives with 50GB free space available on Each drive and XP SP3 installed.

PC-1 (Vickers)
2.13 gigahertz Intel Core 2 Duo
64 kilobyte primary memory cache
2048 kilobyte secondary memory cache
64-bit ready
Multi-core (2 total)
Not hyper-threaded
Board: Foxconn 946 7MA Series
Bus Clock: 266 megahertz
BIOS: Phoenix Technologies, LTD 6.00 PG 12/09/2006
2048 Megabytes Usable Installed Memory
450Watt PSU

PC-2 (Avroe)
2.70 gigahertz AMD Athlon 7750 Dual-Core
256 kilobyte primary memory cache
1024 kilobyte secondary memory cache
8 kilobyte tertiary memory cache
64-bit ready
Multi-core (2 total)
Not hyper-threaded
Board: FOXCONN A6VMX 0A
Serial Number: UY30908054049
Bus Clock: 200 megahertz
BIOS: American Megatrends Inc. 080014 02/19/2009
1920 Megabytes Usable Installed Memory
350Watt PSU

PC-3 (Handley-Page)
3.00 gigahertz AMD Athlon II X2 250
No memory cache
64-bit ready
Multi-core (2 total)
Not hyper-threaded
Board: ECS GeForce6100PM-M2 7.0
Bus Clock: 200 megahertz
BIOS: American Megatrends Inc. 080015 06/04/2010
1984 Megabytes Usable Installed Memory
350Watt PSU

The reason I've posted all that PC drivel is that I've got questions as to which might actually be the better PC ?
PC-1 is the only Intel - Is Intel better than AMD ?  )and it has a 450Watt PSU.)
PC-2/PC-3. Although PC2 is 2.7GHz (PC-3 is 3.00GHz) it has Primary and Secondary Cache which PC-3 does not (I may have to look in to this as I'm sure it has but the OS or the BIOS is not seeing it . .  that's for later though).

So I suppose I would go for
PC-2
2.70 gigahertz AMD Athlon 7750 Dual-Core
256 kilobyte primary memory cache
1024 kilobyte secondary memory cache
8 kilobyte tertiary memory cache
and try and run . .  in preferred order . . Milky-Way,Einstein,PrimeGrid.

I'll get the Boinc Clients updated to 6.12.43 in the next 4 days.

Thank you again for your time and help, it is very much appreciated.

Cheers
Rob
Zydor
Posts: 437
Joined: Mon Nov 01, 2010 12:00 am

Post by Zydor »

You'll notice by the end of this post we are still no where near final card selection, and we will not be for another couple of posts, until all the factors are laid out for you to mull over.

Project List
Your preferred list (in brackets is my addition of primary GPU application[s] )

Milky-Way (AMD optimum, NVidia acceptable alternative but sloooow, needs double precision hardware)
Einstein  (NVidia project, no AMD application, I think its single precision hardware but that needs checking)
PrimeGrid. (NVidia project, but has a slow AMD app alternative, single precision hardware)

First off - and this is real important - ignoring it is a "jump off the Cliff moment"  :) - Single Precision (SP) or Double Precision (DP) hardware. Lots of factors involved, but what it boils down to is Double Precision (DP) hardware is accurate to 12 decimal places, and Single Precision hardware accurate to 8 decimal places. To be DP capable the graphics card needs a  particular type of Floating Point Unit built into it. Its therefore a fundamental design issue by card Vendors, and a key one for you, because, you get this wrong,  you limit yourself for the life of a card to no DP projects which can be a real pain. All cards are SP capable without exception, the question is which are DP capable.

AMD have the better DP capable ratio cards - but careful on broad assumptions, check detail, for now though, park that key thought in the mind. Not all cards are DP capable, and at the budget point you have, need to be real careful as it will be a strong factor in card selection - for now be aware of the issue, and start to get into the habit of absorbing if a card is DP capable or not, and whether or not a Project needs DP cards.

Single Precision Applications will run faster than DP applications - that therefore seems a no brainer, however, go Single Precision Card and  (for example) you'll never crunch Milky Way ... ever ..... so pause, think, and choose wisely. Nose around ask those who crunch there, even join the board and post a question.

Card Vendor choice is going to be a crunch point for you. Its looking like AMD (there's a but coming later), as your preferred Project is Milky Way (needs DP cards), and Prime Grid on your preferred list has an AMD application albeit slow one.

Now the "but", and its a big "But".  Science applications at present are really the purview of NVidia (in the consumer world area of graphics cards) due to their application software (CUDA).  AMD propriatory software (Stream) has been parked up, and AMD are going Industry standard (OpenGL) to write their applications. This makes a lot of sense for AMD (they always take the Long View on Strategy), and their new architecture (GCN) on the new 79XX cards tie into this seemlessly. At your current budget point, you are looking at NVidia for Science Projects, and AMD for Maths projects as a preferred option.  The trip and trap is what the AMD application is written in, if its OpenCL, then ask hard questions and be careful over performance at your budget point.  For 79XX and GCN, this will be the big change for OpenCL, but the latter is outside your sphere at present, just be aware its there so you can recognise the issue and understand where it places itself to avoid confusion, and so you can sidestep the uninformed waffle about this, thats out there in BOINCLand.

PC Hardware
Following seven aspects need looking at (not exhaustive, can epeen nit-pick many other points on hardware, but this will get you 99% there):
Mainboard
Main Memory
SLI/Crossfire Capable
CPU
PSU
Case
Cooling

Mainboard
Check the PCI-E lanes available by looking at the mainboard vendor Site specifications.  You are looking for capabilities expressed as: x16 and/or x8 and/or x4 and/or x1 PCI-E Lanes.  Its likely expressed similar to :  ..... the board has 32 lanes available split into following options ..... blah blah blah..... at a guess yours likely to be x8 slots on the board, x16 slots if your lucky. Just note down the number of card slots for each board, and post the PCI-E lane distribution for each one.

Main Memory
Not usually a factor intodays arena of large quantities of Gb memory stores, but worth checking how much main memory a GPU app needs. Most need around 50-100Mb or less per application instance, but some such as Collatz and a Clean Water application at WCG can use truckloads of memory per application 1Gb+ per application running. All your preferred list are light on memory use so you should be fine - but find out, the knowledge is useful for other GPU related aspects later on.

SLI/Crossfire Capable
Mainboards vary as top what they natively support for dual card setups, and whilst you are only looking at one card, it would be dumb to go down a cul-de-sac ignoring possible expansion in the future - at least find out and keep your options open. While you are there, find out the power draw needs of the board in terms of Watts (its for PSU sizing later)

CPU
Not really a factor for card selection, but just be aware it is a factor for their use. A GPU is utterly dependent on a CPU, a GPU cannot survive or work in isolation. Most times the CPU is only lightly using (say 0.05%) of the CPU capacity, but it can be much more. Therefore there is a drain on CPU capacity albeit only a very minor level, it will however slow any WUs running on the CPU slightly by 3-30 seconds depending on the CPU WU. The ones on your list are well behaved, but go and find out the size of the app in memory, and CPU needs from the GPU, and lodge that as another factor in card selection.

PSU
This topic (and the one on Heat below) is critical and under-rated by too many, who then wonder why they have issues. Graphics cards eat PSUs for breakfast, and pretty much take whats on offer with no fear or favour. Its a Showstopper topic which can take you right back to square one in terms of logic for card selection. With the PSUs you have on your PCs I would use the following planning criteria; 450w PSU plan a maximum draw of 400w keeping 50w in reserve, and the 350w plan on 300w used leaving 50w in reserve (always always always always x 1,000,000 always, leave at the very least 50w spare capacity, ideally only plan to use 60% of the capacity (impossible in your case, but keep 50w  capacity back as spare).  This is likely to limit card choice, might even push you into a new PSU purchase, complex topic we will deal will separately if  it comes to it.  Right now, look at http://www.guru3d.com in their hardware review section for the card you are looking at, go to the power & heat section of the review, and note what they are saying.  You can trust them absolutely - if they said black was white, I'd be rethinking my own logic to date as a result :)  They are good. don't get a downer about this as its likely you will hit a power ploblem - we'll deal with it when the time comes, just note the parameters and size of any problem.

Case
A real doozy of a problem as many are not used to selecting PC Case design based on needs of heat from GPUs.  The problem is GPUs chuck out heat on an Industrial Scale rofl :)  You ignore this at pain of melting motherboard, graphics card, CPU and your power bill.  We will deal with it when card is selected as one of the last (but arguably the most significant) issue to look through. The addition of a (quality) high pressure fan or two at crica £15 each can work wonders in this area, but more later ir can be complex to deal with sensibly as opposed to flippently - just be aware of the issue and importance. More GPU cards have melted, and household power bills been ruined because this was ignored than any other factor.

Well.... thats enough for you to think about this time round, and give you some "homework" to do rofl :)

Depending on your thoughts and findings, we will probably start talking actual card selection and the aspects to look for in the card specifications published by NVidia and AMD, on the next post.

Regards
Zy
Barrie
Posts: 38
Joined: Wed Mar 16, 2011 12:00 am

Post by Barrie »

Zydor wrote:Einstein  (NVidia project, no AMD application, I think its single precision hardware but that needs checking)
It runs on both of mine, so must be single precision.
RWremote
UBT Contributor
Posts: 10
Joined: Wed Jul 27, 2011 1:00 am

Post by RWremote »

Thank you very much (again !).
I'll get to grips with this over the next few days and post my findings (been at work over the last 4 days !)
Thanks a lot for the pointers, what to look for, possible pitfalls and what appears to be the oracle of GPU cards !
I'll be back . . . . . . . .
Zydor
Posts: 437
Joined: Mon Nov 01, 2010 12:00 am

Post by Zydor »

Okie Doke ... while you're away, I'll put together two posts on Cooling and PSUs.

A lot of it will not be immediately applicable, but some aspects of nearly all factors will be, at your initial budget point. Much of the discussion on PSUs and Cooling - in the main- applies to mid and high range GPUs, not your budget entry point. Nontheless they are two critical topics, and although you may end up saying "don't apply" after each factor laid out, take it all in.

The day will come - usually quickly - when the GPU habit strikes, you get bitten by the bug, and you are after more of the same. Its at that point that all very definitely comes into play. So its important to get your head round the basics of the key topics, if only to have the ability to realise/recognise there is an issue in future GPU plans that needs investigation when you move on - not live in ignorance to the smell of burning plastic or blown fuses in your first big non-budget level foray into this - whenever that happens.

Regards
Zy
Zydor
Posts: 437
Joined: Mon Nov 01, 2010 12:00 am

Post by Zydor »

The PSU post promised above  .....


As in all the topics above this only scratches the surface of whats involved, hopefully its complete enough to get you to realise that there is no such thing as "a PSU is a PSU and the expensive ones as just manufacturers making an extra buck". The latter is usually used as a self deluding justification for going cheap on PSU so that the latest dinkie-do piece of hardware can be bought. The PSU is THE most imortant part of a PC, whatever way you cut it, for the simple reason that all other parts without exception, are worth squat without power. Yet too often the PSU is left as an after thought as some kind of drain on the budget.

There is of course practical reality to look at, a budget is a budget, often that can't change, but take in all the principles below - then sit back and reflect on what it really means to you at the price point you are looking at. don't ignore the factors below because they may seem to be above current budget .... the principles are important to take on board as you plan for the future. There is a real world of restricted budget, and that at times impinges, but let it impinge only in the knowledge that you made a balanced imformed choice, not mearly knee jerk bottom line price.

First lets nail a Myth, and add an incentive to learn more.

Nail The Myth
The reality is a PSU will only supply what power you demand from it up to its rated capacity. So if you have a 1500w PSU, but your system only needs 400w, thats all you will get - 400w, it does not burn away 1500w in the background.

The Incentive.
A quality PSU will pay for itself over the life of the PSU compared to a cheap bucket shop PSU, and in effect give you free power for life in comparison to what it would have cost using a cheapie. Its a relatively high cost up front, granted, and its well understood that can be a big issue. However, to abuse a famous advert, a PSU is for life not just for Xmas. Invest in a good one and it will repay many many times over. A few numbers ....

A top of the range Enermax Platimax 850w will cost around £225.  An elcheapo bucket shop 850w about £60.

The Platimax has an efficiency rating of 92%, the cheapo probably around 70% (and 70% is generous overall with cheapo's). Now look at the effect on a 500w power draw for a system:

Platimax 92% means it will draw 543w from the wall socket to provide the 500w. At 14.5p per kilowatt hour, over 24hrs working full time always on 7x24, that will cost £1.74 per day to run. Thats (over 365 days) £635 per year.

Cheapo 70%  means it will draw 714w from the wall socket to provide the 500w. At 14.5p per kilowatt hour, over 24hrs working full time always on 7x24, that will cost £2.48 per day to run. Thats (over 365 days) £907 per year ......  :shock:

So over one year alone, the Platimax will save you £272 in electricity costs compared to an elcheapo, That's £47 more than it cost to buy the Platimax PSU, and without factoring in a power price rise, because it sure as hell is not going to drop in price !!

Now take running costs over a five year period (average life of an elcheapo), the Platimax will save you (compared to an elcheapo)  £1,360 which is enough to buy a damn good PC - and cover the cost of purchase in the first place !!!  Chances are you will also have to buy another elcheapo at the five year point, whereas the Platimax will keep going for another 5+ years. The Platimax has a rated mean time between failure of 100,000 hrs  - or over 11 years - I would be amazed if it did not last 15 years before breaking down. That's important, keep in the mind for later when talking about PSU sizing.  You should size for perceived future useage, not current system.

Moral of the tale ..... DON'T buy cheap PSUs, it's a fools gold road to tread, and an exercise in self delusion.

If you are only using it 4 hours a day to play games and crunch BOINC, price point is different ..... but ...... run the numbers above dividing by 6, you still are well in buying quality. I bought an Enermax 350w in 1998, and finally got shot of it in 2009 when I moved to 5970 cards - it was still going fine, rock solid, I sold it on to a "non-cruncher" for £20.  11 years use ...... saved a bunch on power over 11 years even at the then efficiency ratings.

If you don't pay the power bill, run the numbers past who does or whoever runs the house Budget - usually "Dad" or "The Wife"- and then ask them to buy one for you to save them dosh ..... weeeell it could work if you smile sweetly enough rofl  :toothy7:

Specification
Again the quality supply knocks the elcheapo into touch by a wide margin on specification. The key thing is solid reliable smooth supply without splikes, and flexible modular connection points that will  last you well into the future without a nightmare spagetti junction of molex connectors and power spltters snaking all over the inside of the PC. A key factor is the pinouts on the connectors. From 5XXX onwards connectors needed to be 6 pin, those were in quality PSUs years before. Now, cards need an 8 pin and a 6 pin connector for power. Quality PSUs make available two eight pin connectors per 12v rail, and therefore will cope with card design changes for 5-10 years with no fuss. With elcheapo, often you need to buy another one .....

Rather than go through the list, here is a link to look at. Its the spec for the Platimax range. Its only by studying the spec of a PSU of this calibre that you realise what you miss going elcheapo, and its a lot.

Overall facility

Outline Supply

Cable & Connectors

Guru3d PSU Reviews - this a a MUST Study Section

Sizing
An overthetop rule of thumb .... 250w for the motherboard, hard disks and CPU, plus 50w all up for other peripherals, and add the GPU card(s) will get you in the rough ballpark - huge, huge, holes in that crude calculation (!), but as a rough and ready it gets you into the ballpark area of what you are heading for.  Once you decide so far so good, then get online and use a power calculator - zillions around, google is your friend - and get a better all up total. Bare in mind these calculators are always over the top as the manufacturer is vying to get you to buy the biggest they can. Generally they are about 15% over reality. Here's a good one to get you started, from Enermax:

http://www.enermax.outervision.com/

Another good guide is the power section of Guru3d hardware/Card reviews, well worth checking out:

Guru3d Hardware Reviews: http://www.guru3d.com/category/review/
Guru3d VideoCard Reviews: http://www.guru3d.com/category/Videocards/
Guru3d Power Section AMD HD7970 (overclocked):  http://www.guru3d.com/article/radeon-hd ... ck-guide/3

In an ideal world - and one where the budget allows - again the budget implecations of this are not ignored, but its what you should aim for long term - take the calculated power and add a minimum of 25%, preferably 40% to the power figure to arrive at the prefered PSU rating. The addition is to cope with near future expansion, and the fact that all except the high end range of PSUs have peak efficiency when loaded at 60% of rating. (High end Platimax does not change efficiency level right up to 100% power draw - another factor in buy quality).

These days there should be no issue mounting any power supply in a case, but always check the physical size and the space it has to fit into ..... in the past many were caught by not doing this, although now case manufacturers have adjusted PSU space to suit, so usually there is no drama. Always best to check though.

Could write a book on PSU factors, people have, but hopefully the above is enough to get the mind going and provoke further searching and reading on PSUs before making the final buy decision - and hopefully you now realise there is a lot to it, its not just bottom line price. Certainly the factors above and catchphrases in the referenced articles will give you the ammunition to search meaningfully for further detail and confirmation. Always a good idea to float an initial choice to the forum to get views from others, don't buy in isolation, lots on the forum with  PSU knowledge and experiences, all worth their weight in gold, so tap that experience before finally shelling out the cash.

Regards
Zy
Zydor
Posts: 437
Joined: Mon Nov 01, 2010 12:00 am

Post by Zydor »

The post promised above on Cooling .......

The aim is just to outline cooling issues and solutions to give a basis for further searching and study knowing the overall issues - to make it an all knowing post would be too much, way too long. Much will not apply at a low budget level, but again, as above, its important to open the door a little more as to what's involved so a look into any possible future is obtained, and an informed choice deduced for current needs leaving a path open for possible future needs, as to the path to tread knowing future trips and traps. Lots of dosh saved taking that road rather than the "oh it'll do, slam it in and cool it later" approach. Much of below does not apply to low budget levels, but take it in ..... often a new path opens up with new knowledge that causes you to make different deductions even at a budget level.

The Incentive
Blindingly obvious, but needs to be said - once you move into power gaming or 0verclocking or 7x24 GPU BOINC crunching, you move away from the reasons for current PC Case cooling into a whole new world. If its assumed the current case fans will cope - more in hope than reality - then you are in for a rude shock as components burn out, and budgets fly out the window. It needs to be addressed properly - for the sake of your budget sanity, and in extremis, your safety, look at this properly.

PC Case Design
On medium to high case design, the principle of over-pressure is applied to the design. That means the aim of the system is to provide an overpressure inside the Case above the pressure in the room where it is located. The fans supply the airflow needed for that overpressure. The fans therefore need to force air in to build that pressure. The result is heat is - apart from fan airflow - naturally forced out of the case due to the overpressure. It therefore follows that the fan ability (usually measured as "cfm"), is key, more of that later.

The airflow design should start from the front of the case, forcing air through it,  and out via two openings - the fan at the back, and the fans on the top of the case. Watchout for airflow direction when fitting fans, there is usually two arrows showing "up" and direction of airflow. You end up with a push-pull arrangement - push it in via front case fans, and pull it out via the rear fan and top case fans.

There are classic heat sources in the case that merit attention, sometimes their own fan or cooling arrangement. The use of additional cooling on these sources will obviously depend on what they are, what they are used for, and how long your PC sessions are. However each additional cooling placed on the sources should complement the airflow - not push back in the opposite direction - obvious point maybe, but often forgotten in custom cooling non-OEM builds.

Heat Sources
The following are the heat sources that need to be systematically addressed. Some, arguably most, are not relevant at introductory  low budget levels, but take it all in - it's important to understand what to look for and what to consider.

CPU
Without overclocking, OEM supplied air fans on the CPU are fine, no changes needed - be aware, if it breaks down and the CPU heat safety switch fails, you cook the CPU in about 1 second ........  look after it, keep it free of dust bunnies etc. If overclocking is to be carried out, it will cope with a mild overclock, however, anything more than that, a third party air cooler must be fitted if you are to keep the cpu from melting.  A low cost budget CPU fan circa £20-30 is fine, just enough to take off the edge of the additional heat (at that level the cooler will take off about 10-15 degrees of heat). Serious overclocking to fullest extent of the CPU with additional voltage applied to the cpu, needs a serious cpu cooler, they are around £45-80, can be more, and needs careful planning to ensure it fits inside the case. We'll keep away from makers for this post, just post in forum for suggestions on make and capacity if needed, just be aware of the decision points.

Guru3d Cooler Reviews
Zalman Hi End CPU Cooler
The Rolls Royce of CPU Aircoolers
Akasa X4 low-medium cooler

Reality for most is the Akasa X4 level of cpu cooler, does the job fine - (serious overclocking needs more than this) - it came out 2 years ago, and better one now on the market, but for £20 or so, hard  to beat even now. Its a good start point for mild overclocker, works well.

Water cooling is a good thing, almost essential with high end rigs seriously overclocked, a whole topic on its own, so leave it at that for now. A "halfway house" solution does bare highlighting. The Closed Loop cooling. The latter is a relatively recent innovation gaining wide popularity in mainstream use, that cools just the CPU, by use of a sealed system. Its just a water block on the CPU, leading to a radiator and fan clipped inside the case, usually in place of the back case fan. Its a very good idea, and ensures heat is dumped outside the case, not inside as air based cpu coolers would. Price can be a little more than high end cpu coolers, but very worthwhile, they do a good job. A good one is the Corsair range of closed loop coolers, url below ..

Corsair Closed Loop Cooling Systems

GPU
The GPU is the bad boy of PC heat, surpassing by far the heat produced by a CPU. You need to be most careful on the amount it punches out and what you do with it. Increasingly GPUs are inside closed case fans attached to the cards that blow air outside the case, however, that's not the whole story. The reverse side of the card is open to the air inside the case, and therefore what you do with case cooling has a direct impact on the GPU. Is it the worlds biggest problem - no - but its ignored at the cost of a melted card, or even worse other case components get overheated with its output. Low end budget priced cards can usually be dealt with by just turning up the case fans, and paying careful attention to the speed of the actual video card fan, and you are fine.

Medium and especially high end cards must have particular attention to their heat output. Solutions range from fitting high pressure fans to case replacing the original fans (circa £15 each), or fitting third party fans to the card(circa £80 each), or going the whole hog and fitting water cooling to the card. For most people turning up the case fan and card fans will do fine. If you have a beast of a card then fitting pressure fans in the case, and third party fans may well be your only option if you overclock the card. In all cases, the card cooling is usually fine as is, if you don't overclock the card, in the  latter cases just turn up the card fan as needed, and/or fit pressure fans to the case suits most needs except the real hard card overclocker..

Its hard to be definitive as it depend on what else is going on in the case that also emits heat. In all instances though, airflow is the absolute key, and fitting pressure fans if using anything other than low end budget cards is a must if you are to avoid problems. It is far far better to fit pressure fans first before using other third party solutions as this benefits the whole case, not just cards, and also lowers the case temperature (that affects the level of the card temperature).

Low budget end has no issue, just turn up the card fan and case fans.

Voltage Regulators.
This really only affects high end machines and high end cards, with one exception. The issue is the circuitry that changes and supplies the voltage to both the motherboard and VideoCard gets very hot if overclocking, and on high end boards, still gets hot in normal use. On budget machines or budget cards its not an issue, but its where the motherboard will burn out if you do not pay attention to overall case cooling, so be aware of the problem, keep that air flow pushing hard through the case, whatever level of crunching you are doing. Card VRMs are usually taken care of by the card cooler (less the nasty design issue on 5970s), and if needed motherboard manufacturers will fit VRM coolers to the motherboard on high end stuff.

So at a budget or medium level, not really an issue, but can be if you don't keep the airflowing hard - pressure fans are the simple and very effective solution to airflow.

Fans
There are too many to count on the market, just be wary of cheap fans, they just dribble out air and flash a blue light, but thats all they are good for - less than useless. Fans of less than £5 a throw are just good for the dustbin. Don't bother. £5-10 a go are suitable as a standard Case fan, and really for any decent worthwhile pressure fan you'll pay £15-20 a  fan. The spec to look for is the "cfm" value. A decent pressure fan is around 60-100 cfm, they will go to 150+ cfm, but the latter sound like a jet engine in the room. Usually, given a quality maker, cfm around 60-90 should be good to go and noise level is fine, some are actually quiet (!).

cont>>
Barrie
Posts: 38
Joined: Wed Mar 16, 2011 12:00 am

Post by Barrie »

One thing to consider with water cooling, especially with the CPU only closed loop type system is that other nearby-ish air cooled components might well be expecting/relying on a draught from the CPU fan...
UBT - Timbo
UBT Forum Admin
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Re: The Black Art of GPU computing ! Help.

Post by UBT - Timbo »

<<cont:

I can't emphasise enough the effectiveness of pressure fans, they solve many evils and are a brilliant investment. On the recent rebuild of my main box I took out the case fans (30 cfm), and replaced the lot with 90 cfm fans, the centre front case fan being a 110 cfm fan. I fitted a closed loop cooler to the cpu, and now all heat issues have disappeared. Its only lukewarm, at times cold, air coming out the top case fans - and that's with an overclocked 3960X cpu and twin overclocked 5970s inside. Don't knee jerk expensive third party coolers until you have sorted out case fans, even just one or two on the front fans are often enough to make a very significant difference.

Thats it really - just enough to open the door on the overall issues so further study/investigation can occur. The overall message - airflow, airflow, airflow .......  then think about airflow. Get that right, and from that point on you only need specific (expensive) third party cooling solutions for high end overclocking and crunching. A little thought, time and effort into researching fans will save a ton of cash, and solve most problems.

If you seriously overclock ..... well, its a different ball game involving more than fans :)

Monitoring
A plethora of software out there for monitoring temperature and fans. Some classics to get going, then investigate your own preference over time - Speedfan, CoreTemp, CPUID range including their HWMonitor, CPU-Z, GPU-Z .... dozens out there, but get them and use them to monitor all this, else you will overheat .....

Regards
Zy

admin edit: hard to split this reply, due to word length issues.
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