PCI Latency?

[jpetermann]

What should I set this to for my a7v8x? I have never messed with this is my bios before. Mine is set at 32.

Thanks for the info,
PJ

 

[AndyHui]

Normally it is 32 or 64. 32 is supposed to be a "fair play" setting, while 64 seems to give the best performance.

 

[John]

I have an Epox 4BDA2+ and mine is set at ZERO (0) by default. I wonder if I am losing any performance?

 

[Jeff7]

I haven't noticed any performance changes by altering my PCI latency. The only things I've ever noticed was increased crashing at various settings.
My AGP card had its latency set to 255clks; I set it to 0, and I think it affected my 3dmarks score by a couple of points; just the usual variation from one testing to another. It did make the system more crash prone though during games.

 

[jrichrds]

My Asus board has PCI Latency at 64 as default, and recommends this setting for best performance.

Edit: My bad, 32 is default on my Asus board, and is the setting recommended by them.

 

[aceO07]

My ASUS P4B533-V has it default at 32.

 

[oldfart]

My 4BDA2+ is set to 32 by default. John, not sure why yours is at 0, but I would set it to 32.

 

[Bobbyeyes]

THUGSROOK did an elaborate test and posted his results in the usual elegant fashion.
a paste from his thread(i dont think he will mind):
Thugs post
after alot more testing im now using a latency of 96

here's some scores for ya monky...

PCI Latency >>> 0 - 32 - 64 - 96 - 128

3DMark2000:
16110 - 16159 - 16171 - 16182 - 16175

3DMark2001se:
12294 - 12294 - 12295 - 12335 - 12330

Sandra: File System
25068 - 25076 - 26736 - 26977 - 26973




__________________
1.6A @ 2.61ghz (1.7v) 163fsb 435ddr CAS 2-3-2
P4B533 / XMS3000 / GF4 ti4600


Last edited by ThugsRook on 08-21-2002 at 11:54 PM

 

[jrichrds]

That's interesting. I wonder if it's dependant on what components you have in your system.

 

[John]

Sandra 2002 SP1 file system bench (dual D740x "L" in raid 0 w/ 64K stripe)

PCI Latency 0 - 42K+

PCI Latency 64 - 45K+

 

[Rubben23]

THis is taken from www.rojakpot.com BIOS GUIDE


PCI Latency Timer
Options : 0 - 255

This feature controls how long each PCI device can hold the bus before another takes over. The larger the value, the longer the PCI device can retain control of the bus. As each access to the bus comes with an initial delay before any transaction can be made, low values for the PCI Latency Timer will reduce the effective PCI bandwidth while higher values improve it.

On the other hand, while increasing the value lets each PCI device access the bus longer, the response time of those PCI devices suffers as a result. That means every PCI device will have to wait longer before they can get access to the bus but when they do get access, they can conduct their transactions for a longer time.

Normally, the PCI Latency Timer is set to 32 cycles. For better PCI performance, a larger value should be used. Try increasing it to 64 cycles or even 128 cycles. Some PCI devices may not agree with longer latency times so if you start facing problems like stuttering sound or a less responsive system, reduce the latency. Higher values will actually reduce performance as too much time may be allocated to each PCI device to the disadvantage of other devices on the bus.

 

[Peter]

Exactly like that. Larger values allow for higher throughput of the device that currently owns the bus, but raises the access latency (hence the name) for all the other devices that have a transaction pending and wait for their ownership request to be processed. Set it too low, and transfer rates suffer. Set it too high, and you'll have your realtime streams break up, noticeable as jerky video or scratching, popping sound.

Yes the "right" setting depends on what you have, this is why it's adjustable.

regards, Peter