Hello I have 2 x ATI Radeon 4800 series graphics cards that are in crossfire mode. I have under clocked them, and tried to throttle their speed but neither BOINC or I can do ir.
I need to slow down GPU crunching because the temp peaks at 120oC

Hello I have 2 x ATI Radeon 4800 series graphics cards that are in crossfire mode. I have under clocked them, and tried to throttle their speed but neither BOINC or I can do ir.
I need to slow down GPU crunching because the temp peaks at 120oC

Unless you also game cross-fire is NOT helpful to crunching, but I am not sure that will lower the temps. This program MAY help in limiting your temps:
http://download.cnet.com/TThrottle-Temperature-Throttle/3000-18512_4-10909149.html

120C!!?? Wow! your going to kill them at those temps!
Are you sure their running that hot? My 4870 used to error in OCCT at mid 90sC IIRC.

Can't you speed up the fan via CCC or other software?

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Team AnandTech - SETI@H, DPAD, F@H, MW@H, A@H, LHC, POGS, R@H, Einstein@H, DHEP, WCG

Main rig - Ryzen 5 3600, MSI B450 G.Pro C. AC, RTX 3060Ti 8GB, 32GB DDR4 3200, Win 10 64bit
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Hello I have 2 x ATI Radeon 4800 series graphics cards that are in crossfire mode. I have under clocked them, and tried to throttle their speed but neither BOINC or I can do ir.
I need to slow down GPU crunching because the temp peaks at 120oC

You can also change the default Boinc settings so you only crunch 50% of the time, that should cut some of the heat production, not 50% of it but some.

I don't think it's possible to run the GPU at 120 C. What tool do you use to monitor it?
You might try to undervolt it. I do this with my 7950's which had VDDC=1.25V default, but fortunately have digital PWMs, so it's fairly simple to change the voltages.

120°C?! You sure you don't mean 120°F = 49°C?

You can also change the default Boinc settings so you only crunch 50% of the time, that should cut some of the heat production, not 50% of it but some.

I'm not sure this works for GPU apps (IIRC not) and even for CPU apps it's better to use 50% of processors instead.

For GPU app I'd recommend using cmd parameter like --gpu-polling-mode via app_info or app_config file (not sure if the current OpenCL apps have exactly this one, that's from the CAL app, but maybe someone who actually uses them could check).

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Hmm, seems the op is MIA!

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Team AnandTech - SETI@H, DPAD, F@H, MW@H, A@H, LHC, POGS, R@H, Einstein@H, DHEP, WCG

Main rig - Ryzen 5 3600, MSI B450 G.Pro C. AC, RTX 3060Ti 8GB, 32GB DDR4 3200, Win 10 64bit
2nd rig - i7 4930k @4.1 GHz, HD 7870 XT 3GB(DS), 16GB DDR3 1866, Win7

I did use CCC to reduce gpu and GDDR speeds it reduced the temp.
When idle these cards sit at 55oC and at lowest settings by CCC the temp sits at up to 79oC on workloads.
The motherboard I was using allows CCC to utilise the overdrive feature but i switched to Gigabyte DS2 because the ASUS i accidently damaged and overdrive app feature doesnt load on this board lol switches to some screen gui.
advice about crossfirex is appreciated :)

even if it wasn't 120oC it was hot enough to see a mini heat wave eminating from the underside of the GPU card so i swiched it off.

I did use CCC to reduce gpu and GDDR speeds it reduced the temp.
When idle these cards sit at 55oC and at lowest settings by CCC the temp sits at up to 79oC on workloads.
The motherboard I was using allows CCC to utilise the overdrive feature but i switched to Gigabyte DS2 because the ASUS i accidently damaged and overdrive app feature doesnt load on this board lol switches to some screen gui.
advice about crossfirex is appreciated :)

even if it wasn't 120oC it was hot enough to see a mini heat wave eminating from the underside of the GPU card so i swiched it off.

Yes gpu's DO get very warm when they crunch, after all they are running at nearly 100% load, 100% of the time. There IS software you can use to slow it down a bit, MSI Afterbuner is just one that should work on your AMD cards. Getting the right mix that works for you AND allows you to crunch though will take some time and tweaking on your part, but it is NOT hard. You WILL learn alot in the process too!

Also, projects like this, which use double-precision load the GPU execution units higher, so that causes additional heat. In my case (HD7950, R9 280X) the GPUs run ~10 C hotter than on other projects with single-precision math.
You might need to undervolt your GPUs if possible. I do this too, otherwise they would run too hot.

Maybe at beginning some simple things to check:
dust on coooler's fins
fan rpm
air circulation in chasis
remove one GPU to improve air circulation.

Maybe at beginning some simple things to check:
dust on coooler's fins
fan rpm
air circulation in chasis
remove one GPU to improve air circulation.

I have one pc I actually have an external fan pointed into just to keep it cool! The older cases are not designed for the newer airflows needed for the HUGE gpu's we are putting in them.