Is there any advantage to cross-firing a headless dedicated Boinc cruncher? Would the answer make a difference if matched or unmatched cards? Thanks, just wondering for future purchase decisions. Currently most my experience is with Nvidia cards; in which SLI and Boinc cannot be used together.

It's easier to set up :) Means you don't have to faff around sorting out the second card to crunch. A matched card makes it a lot easier in my experience. Also, more cores helps for the time being...

Now I would like to know whether I shall get approximately the same points/day with a 4870x2 than two 4870 single cards?

If you have a second card in the system, you reduce the CPU:GPU ratio, meaning that you have more chances of running out of work. It's the same if you use two seperate cards, or one X2 card, though with two seperate cards if you come across anotehr quad core machine, you can move it over there. I find 2CPU:1GPU a good minimum ratio - a 1:2 ratio means your cache will be sucked try in about 3-4 minutes. I plan to supply my i7 machine with two 3850X2s come pay day...

Enable Crossfire via the CCC.

I have TWO 4850X2s in one system and they work fine with Crossfire enabled.

Or to cite one of your WU's task details:

CPU time 78.30197
stderr out <core_client_version>6.6.20</core_client_version>
<![CDATA[
<stderr_txt>
Running Milkyway@home ATI GPU application version 0.19f by Gipsel
allowing 2 concurrent WUs per GPU
CPU: AMD Phenom(tm) II X4 940 Processor (4 cores/threads) 3.0002 GHz (425ms)

CAL Runtime: 1.4.283
Found 4 CAL devices

Device 0: ATI Radeon HD 4800 (RV770) 512 MB local RAM (remote 2047 MB cached + 2047 MB uncached)
GPU core clock: 625 MHz, memory clock: 250 MHz
800 shader units organized in 10 SIMDs with 16 VLIW units (5-issue), wavefront size 64 threads
supporting double precision

Device 1: ATI Radeon HD 4800 (RV770) 512 MB local RAM (remote 2047 MB cached + 2047 MB uncached)
GPU core clock: 625 MHz, memory clock: 250 MHz
800 shader units organized in 10 SIMDs with 16 VLIW units (5-issue), wavefront size 64 threads
supporting double precision

Device 2: ATI Radeon HD 4800 (RV770) 512 MB local RAM (remote 2047 MB cached + 2047 MB uncached)
GPU core clock: 625 MHz, memory clock: 250 MHz
800 shader units organized in 10 SIMDs with 16 VLIW units (5-issue), wavefront size 64 threads
supporting double precision

Device 3: ATI Radeon HD 4800 (RV770) 512 MB local RAM (remote 2047 MB cached + 2047 MB uncached)
GPU core clock: 625 MHz, memory clock: 250 MHz
800 shader units organized in 10 SIMDs with 16 VLIW units (5-issue), wavefront size 64 threads
supporting double precision

2 WUs already running on GPU 0
2 WUs already running on GPU 1
2 WUs already running on GPU 2
2 WUs already running on GPU 3
No free GPU! Waiting ... 18.892 seconds.
Starting WU on GPU 1

I would think you could gain a tiny bit of performance if you raise the memory clock slightly. It's a 4850X2 with only GDDR3 after all (even on a HD4870 with GDDR5 250MHz reduce the performance by ~5% already). Furthermore, if you enable crossfire the memory contents for the GPUs are duplicated, thus raising the bandwidth requirements.

wow...
Your the only project that runs ATI and instead you come out with a CUDA GPU app instead of finishing the ATI WU app...
Sorry if this sounds harsh but it is just the way I feel.

I think my R.A.C. started to go up just looking at that MB!!!!
;-p

That is not your RAC.


This is a very sweet board. Feasibly 4x16 PCIe slots. - loaded with over clocked Dark Knight 4870's 400K per day.

Very nice.

Saenger ....Are you the credit Police? What is your problem dude...1st Cosmo now here! Credits here were voted on...every vote counted to the credit we receive(including yours)....I thought credit discussion was done here....always at least one guy that likes to stir it up.Are you employed by DA?Apparently you perfer gestapoism to democracy...Please just go crunch projects with no credit and leave the rest of us in peace.....Grrrrrrrr

sysfried, my quad goes idle too if I let it download "the full" 20 work units. I got around that by setting a very small cache (0.02 days). Boinc then downloads only a few work units, and doesn't defer communication. When 2 or 3 WU are finished, it just downloads new ones. As long as there are WU available from the server, this scheme works fine.