PCI Latency

[Gamingphreek]

I was reading and posting a bit over at Guru 3d and i figured i would check this out.

Basically people are experiencing varied results, some lower CPU utilization, some better sound quality and some netter framerate.

Thought AT might want to check it out and see what its like:

Guru3d Home

The Forum discussion thread

Download Mirror

I will try when i get home. Anyone else who wants to i think we would all be interested in results.

-Kevin

 

[Squally Leonharty]

It might be handy to know that ATITool also offers PCI Latency adjustments. ATI owners seem to get by easily with this all-in-one program. *changed latency from 255(!) to 64*

I'll test it later, though. >_o

 

[Peter]

That "latency" is actually latency FOR OTHERS while the particular device owns the bus. Larger values improve maximum throughput for devices that transfer large amounts of data, smaller values improve fairness amongst multiple devices on the same bus.

E.g. if you have a storage controller and a sound device on the same bus, larger common values will improve burst throughput on the storage, but cause interruptions in the data stream to/from the sound card and cause crackling and popping.

On the AGP port, where there are no other agents besides the AGP card and the host chipset, and inherently there need not be any fairness, tweaking the latency is rather pointless. Go for maximum values. (Depending on the chipset, there might be side effects on other busses, and in those cases lower AGP latency values might actually do something.)

 

[kamranziadar]

thanx for explaination

 

[Appledrop]

i have nothing in my pci slots, so this is useless, right? only for people with pci soundscards am i right?

edit:, well i tested this with the spinning cube in ATItool, and repeated tests twice to see its not freak ...


with latency=255, averaged at 412 FPS
with latency=32, averaged at 412 FPS

oook...

 

[Gamingphreek]

AGP is technically PCI slot 0. So it might to something to your graphics card as well. Not sure.

THanks for the benches. I will check and bench as well.

-Kevin

 

[Peter]

No it's not. AGP is technically a 66 MHz PCI bus of its own, with extensions to make it faster, and no provisions for more than one device.

 

[Gamingphreek]

Yes it has its own dedicated "PCI" bus. However it still runs based on the PCI Bus. THe PCI bus just runs at a divider compared to the AGP that is why you there is a PCI/AGP lock rather than an AGP lock and a seperate PCI Lock.

I agree with you however.

-Kevin