Second G/Card NOT SLi

[pENdr4gON]

Hi guys and gals, I have been thinking, and it hurts...

I was reading about nVidia's PhysX on the Guru of 3D site. It was mentioned there the possibility of running a second card in the 8XXX serices. Useing it as a PhysX card not as part of an SLi setup. Nvidia 8400 cards can be bought for as little as £25. Put it in the second PCI-E slot and tell nvidia PhysX to use it to do the maths, letting your beefy card to do all of the 3D stuff as normal.

What do you think?

 

[Rroff]

From what I've seen the lowest card thats worth using for dedicated physics processing is the 8600GT.

 

[UKDTweak]

Was considering this myself as i have an 8800GTS 320 sitting spare, sadly my MB only has one PCI-E slot

My current board is a Gigabyte 965P DS3, i need a new board that can support this and still clock well without breaking the bank. any good boards for under £90 that fit the bill, so many to choose from and so many opinions.

 

[Rroff]

Any of the P35 boards will clock well and a good many have dual PCI-e x16 slots (tho IIRC the 2nd one doesn't run at x16). (I'm a big fan of the gigabyte P35 DS3 series).

Theres also a gigabyte P46 at ~£90 tho I don't have much experience with the P45 chipset.

 

[Monkeynut]

The P35 second slot runs at x4.

 

[UKDTweak]

If the card in the second slot is only going to be used for Physix, how important is the bus speed of said slot? I.E: 4x, 8x or 16x ???

Thanks for the info

 

[Rroff]

Upto a well clocked 8800GTX an 8x slot would be fine - so something around an 8600GT wouldn't probably be that limited even by a 4x slot. I would imagine tho Physics calculations do make quite heavy use of the bus bandwidth.

 

[reflux]

I don't think the current driver supports assigning PhysX to different cards/parts of the GPU?

 

[pENdr4gON]

Well I couldn't wait...

Slapped a 8400GS 256Mb PCI-E card in the second slot. Told PhysX to use the 8400 to do the maths and it was as you guys suggested a desaster! Well on the simple PhysX benchmark supplied with in the driver pack.

Test results:

MKZ Benchmark

Before I changed anything
AVG 21
Min 5
Max 37

8400 doing it's thing
AVG 9
Min 6
Max 10

With the 8400 installed but my 8800GTS doing it all on it's own but 8bit rather than 16bit
AVG 20
Min 5
Max 35

There would apear to be variations in the results you get from this benckmark. At this point I'm not sure if it's a bandwidth issue or simpaly that as suggested the 8400 dosn't have the balls to do the maths involved.

See if I can lay my hands on a 8600 to do some more tests. It dose prove that if you wish you can set up an SLi MoBo in duel card setup with different cards and get one to the math and the other the 3D.

 

[Rroff]

Yes they do - infact I think with 2 video cards present then the 2nd card will automatically be assigned to physx by the driver - atleast with my 8800GT SLI thats what happens if I disable SLI mode.

 

[Rroff]

Cheers for the benchmarks - shame you had to be the guinea pig but as I suspected the 8400 just doesn't have the horse power - if you do get a chance to test some other cards please report back.

 

[Monkeynut]

8600GT has 4 times the stream procs and would flatten an 8400.