BIOS - PCI Bus Limit

[xxJohnxx]

Hi,

 

Yesterday I messed up my BIOS. While trying to fix what I have done I came accross the option: PCI Bus Limit. By default it was set to 64. As I was curious, I set it to 256.

Later, when I got my system running again, I did another benchmark in DCS, and I noticed an performance improvement of 30-50%.

This made me wonder, what is that PCI Bus Limit option? I wasn't able to find much online, so I am hoping for an answer here!

 

Thanks,

 

John

[Kuky]

As far as I recall it's the time limit for any device on the PCI bus, to access the PCI bus lanes. If for example data from device needs 256ms to transfer the data over the bus, and this limit is lower than that, the extra data needs to wait next cycle.

[Mustang]

Isn't this just the PCI Latency Clock Timer setting? this has been on motherboards for over a decade, i just left mine on 128 ages ago and forgot all about it until now :)

[Cali]

Isn't this just the PCI Latency Clock Timer setting? this has been on motherboards for over a decade, i just left mine on 128 ages ago and forgot all about it until now :)

 

I remember a trick like this 8+ years ago.

[SkateZilla]

My system doesn't have those settings in the UEFI, but I know my AM2 System Did, hmmm,

 

PCI Bus Limit / PCI Latency is Measured in Clock Cycles

If Latency Timers are Low (32, 48, 64, and even 128 Clock Cycles),

Devices can interrupt each other while sharing the PCI Bus. Which can effect performance.

 

I believe 5 or so years ago, 128 Cycles was the recommended setting for Gaming GPUs. that was the 8800 GTX Era

 

Setting it too high can cause buffer overflows, So Be Careful.

 

Leaving this setting on 64 Cycles or Lower while using onboard audio processor can cause stuttering and low FPS.

Edited February 27, 2014 by SkateZilla
Fixed my broken finger typos

[Milli]

I checked mine and it was set at 32. Have changed it to 128 as SkateZilla said above. Seems to be running fine.

 

Regards,

Milli

[xxJohnxx]

Thanks for your replies guys!

 

The bios has two options on the same page regarding the PCI bus.

 

- PCI Latency Clock Timer

- PCI Bus Limit

 

From what I could understand you all where talking about the first one.

Is the second one a similar thing?

 

Thanks!

 

John

[SkateZilla]

what is the make and model of your mainboard so I can look up the chipset?

[xxJohnxx]

It is the Intel DZ77GA-70K.

[SkateZilla]

I dont see a PCI Bus Limit setting in the BIOS menu.

[xxJohnxx]

See the attached screenshot.

 

The photograph is quit old and you will notice, the PCI Latency Clock Timer is not on this particular screenshot. It was added with an update right above the PCI Bus Limit option.

[SkateZilla]

pretty sure it's the same thing