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afo
Adept I

SDK 2.3 and multiGPU

First impressions on multiGPU for the new SDK in HD5970

Hi,

I would like to share some insights about multigpu in SDK 2.3 (WinXP32 & Linux64), and yes, I know that AMD officially doesn't support the second GPU on the HD5970, I hope they will give support before xmas 2011...

WinXP32:

cal findnumdevices shows 2 devices; clinfo shows 2GPUs + 1 CPU (in inverse order, now there is GPU data first and then the CPU data)

My application has a parameter on which GPU work; 0 for the first one, 1 for the second and so on; I used to have 2xHD5970, I moved one to another machine. If I use GPU 0,everything goes fine, if I use GPU 1; the application crashes...

Linux64

Again, cal findnumdevices shows 2 devices; clinfo shows 2GPUs + 1 CPU

if I open 2 terminals, two instances of the application using different GPUs can work and give correct results. But system performance drops down: moving a terminal window goes in slow motion (this didn't happen with SDK 2.2), the four processors in my system are working at 80% and ati-config shows 30%usage for the first GPU and 70% usage for the secong GPU (with minor variations).

I would like to know if someone see something similar or has different experiences. Thanks a lot

best regards,

Alfonso

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32 Replies
dravisher
Journeyman III

SDK 2.3 and multiGPU

Pretty disappointing that the HD5970 isn't supported yet

Don't know if anyone from AMD can answer this, but will the upcoming dual-GPU card based on Cayman chips (presumably HD6990) also not be working correctly with SDK 2.3? Currently I want to wait for that, but if have to wait for an unspecified amount of time for dual GPU + OpenCL to work I'd rather just get a HD6970.

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himanshu_gautam
Grandmaster

SDK 2.3 and multiGPU

Dravisher,

There are no plans for launching a 6990. Where did you got this information?

 

Edit: Thanks nou for clarification. I was not aware of this at that time.

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nou
Exemplar

SDK 2.3 and multiGPU

all over the internet. for example here http://news.softpedia.com/news/Dual-GPU-AMD-HD-6990-Pushed-Back-to-Q1-2011-165713.shtml

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zeland
Journeyman III

SDK 2.3 and multiGPU

Multi-gpu issue did not solve in sdk 2.3 in linux x64.

I run two instance of one program on two different 5870 card.

two instance  run in 550 seconds each in parallel . And one instance take only 320 seconds.

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dravisher
Journeyman III

SDK 2.3 and multiGPU

Originally posted by: himanshu.gautam Dravisher,

 

There are no plans for launching a 6990. Where did you got this information?



That the dual-GPU card will be called HD6990 seems to be the general consensus in the media, like the article nou linked to, but to be fair the only info from AMD is that a dual-GPU card named "Antilles" is coming in Q1 2011. For instance in the AMD Codename Decoder – November 9, 2010 blog:

“Antilles”
Market: Discrete GPUs
What is it? AMD Radeon™ HD 6000 Series graphics card for ultra-enthusiasts that will feature two GPUs on one board.
Planned for introduction: Q1 2011


 So I guess the proper question is: will Antilles have both GPUs working properly with OpenCL at release?

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nou
Exemplar

SDK 2.3 and multiGPU

no. why do you think that new dual card will work when current multi GPU didn't work?

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d_a_a_
Adept II

SDK 2.3 and multiGPU

Originally posted by: nou no. why do you think that new dual card will work when current multi GPU didn't work?

 

Maybe the current dual-GPU card (5970) has a design error that precludes it from being properly supported as two GP-GPUs.

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emuller
Journeyman III

SDK 2.3 and multiGPU

I have a 5970 and I'm using both GPUs using CAL under Linux where each GPU gets its own controlling *process* (using "multiprocessing" in python), i.e. I am not using threads.  The two GPUs do work concurrently (I do recall memory copies host<->device for the two GPUs seemed to be serialized though).  The results also seem to be OK.  I am currently using Catalyst 10.10 and SDK 2.2 with my 5970.

So is it possible its with OpenCL that the 5970 is not supported?  Or is it possible that you can get it to work using processes (MPI, ... or in python PyOpenCL and "multiprocessing") instead of threads?

BTW, on my other box using 10.12 and 2.2 SDK, 2D problems such as described by afo appear, such as improper scolling in windows, slow window moving ... which I could address by enabling desktop effects (rendering is done by OpenGL then I presume). So this is a 10.12 problem, and not a 2.3 problem I guess.  Either try 2.3 with 10.10 or enable desktop effects as a work around.

 

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dravisher
Journeyman III

SDK 2.3 and multiGPU

Originally posted by: nou no. why do you think that new dual card will work when current multi GPU didn't work?

 

Surely if a software fix is so difficult, they would change the design of the next dual-GPU card so that it will work. Hard to say since I know next to nothing about what the problem is, but I would think AMD could fix it in hardware if they wanted to.  For instance if the problem is the always-on crossfire, they could make it easier to toggle crossfire off on the upcoming card.

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