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PCI Latency Timer
http://www.mysterybyte.com/phpBB3/viewtopic.php?f=8&t=878		 Page 1 of 1
Author:  skiman [ Sat Jul 26, 2008 11:37 pm ]
Post subject:  PCI Latency Timer
The PCI Latency timer is a bios option of most systems. Default is 32 with a range from 0 to 255.

I was playing with this option and decided to bench under Vista 32.

3DMark06

Latency 1 - 18720

Latency 255 - 18378

That is a good increase under Vista.

Can anyone confirm this on their system?

Cheers
Author:  Monkeydee [ Sun Jul 27, 2008 12:51 am ]
Post subject: 
a question, did you have any pci or pci-e cards installed other than your video card(s)?
Author:  skiman [ Sun Jul 27, 2008 10:05 am ]
Post subject: 
No other cards,

The image below shows the 790i bus in block form. While the PCI latency timer itself is not directly associated with the PCIe 2.0 bus via the SPP, it should indirectly affect the SPP by reducing the time MCP devices can retain control of the PCI bus.

Would this reduce the percentage of time the SPP is communicating with the MCP?

Image

While benchmarking at Latency 1, I did notice the load time was longer.

The bench in the first post was SLI'd. I'll try benching in Tri SLI with the latency set at 1 and 255. According to the diagram above the third PCI x16 slot should see gains.

Cheers
Author:  Monkeydee [ Sun Jul 27, 2008 1:57 pm ]
Post subject: 
to the best of my understanding on this topic, which is admittedly limited, the more devices you have the higher you'll want the latency because with a latency of 1 a single device will crowd the bus causing other devices to not be able to send and receive data.
so i'm kind of curious as to how your system will behave with a couple additional cards and maybe a couple USB devices hooked up while benching with a latency of 1.
Author:  skiman [ Sun Jul 27, 2008 2:27 pm ]
Post subject: 
As per the diagram above, I do have is a few ESA devices, 4 SATA drives, CD/DVD, Audio, internet, and a few usb devices.

Disabling these devices via the bios for highend benchmarking does have positive results.
Author:  Dr_BenD_over [ Sun Jul 27, 2008 5:01 pm ]
Post subject: 
I don't appear to have such an option.
Author:  skiman [ Sun Jul 27, 2008 6:27 pm ]
Post subject: 
It appears that you do not.
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