Should Video Card's PCI Latency Be Lowered?

[Akumajo]

Adjusting PCI Latency in BIOS does not affect video card's latency, but PCI Latency Tool can. Should the video card's latency be left alone at 200+ or lowered to come in line with the rest of the system's latency of say 64? Why is the video card immune to PCI Latency changes in BIOS? What does ARP recommend?

[Adrian Wong]

Originally Posted by Akumajo

Adjusting PCI Latency in BIOS does not affect video card's latency, but PCI Latency Tool can. Should the video card's latency be left alone at 200+ or lowered to come in line with the rest of the system's latency of say 64? Why is the video card immune to PCI Latency changes in BIOS? What does ARP recommend?

Hello Akumajo,

That's because the AGP card isn't directly connected to the PCI bus.

The BIOS option you are looking for is actually AGP Secondary Lat Timer - http://www.rojakpot.com/showFreeBOG....ng=0&bogno=144

Hope that helps you some!

[Akumajo]

I don't have that BIOS setting. Your description says normally it's set to 32, but most if not all video cards have latency at 250 or whatever (I forget the exact number). It goes on to say that if the AGP latency is set to a very large value, it is recommended to set the PCI Latency to 32... I'm confused. What's best, leave PCI Latency at 64 and the AGP Latency at it's default of 250 or change the AGP Latency to 64 to have it the same value as everything else?

[eLPuSHeR]

I have lowered mine using PCI Latency tool and I have found that is running quite well at 32. Your mileage may vary. You may need to do some testing.

[Adrian Wong]

Originally Posted by Akumajo

I don't have that BIOS setting. Your description says normally it's set to 32, but most if not all video cards have latency at 250 or whatever (I forget the exact number). It goes on to say that if the AGP latency is set to a very large value, it is recommended to set the PCI Latency to 32... I'm confused. What's best, leave PCI Latency at 64 and the AGP Latency at it's default of 250 or change the AGP Latency to 64 to have it the same value as everything else?

Frankly speaking, I don't understand what you are trying to tell me.

But let's get one thing straight first - PCI is NOT the same as AGP.

No. 2 - The PCI Latency BIOS feature controls the latency of the PCI bus. It does not control the latency of the AGP port.

No. 3 - If YOUR motherboard's BIOS does not have that BIOS feature, that doesn't mean it's not there. It's just hidden.

No. 4 - There's no such thing as what's best for BIOS options. If there's a perfect setting for every BIOS option, then the motherboard manufacturers will just use that setting and we won't have to crack our heads figuring out the best settings for our system.

Okay, now, let me clarify it for you. The two BIOS features (PCI and AGP latency timers) allow you to modify how much time PCI devices and AGP devices can take hold of the PCI bus.

If you want more time for the AGP card, well, just increase the latency. But as I've said in the guide, the more time you allocate to it, the less there is for PCI devices. You may even face problems with them.

You will need to play with both BIOS features to find the sweet spot for YOUR system. No one here can tell you that because every system is different. Different hardware, different software, etc.

[Akumajo]

I'm wondering if the AGP latency is SUPPOSED to be at that high value, and if lowering it could be harmful. I'm concerned that maybe it is meant to be that high because the video card is always in use, unlike other components.

[Adrian Wong]

Originally Posted by Akumajo

I'm wondering if the AGP latency is SUPPOSED to be at that high value, and if lowering it could be harmful. I'm concerned that maybe it is meant to be that high because the video card is always in use, unlike other components.

Most motherboards have the AGP latency at a high value for obvious reasons. But whether that is acceptable to your PCI cards is another matter altogether.

Okay, simply put, if you don't notice any issues with your PCI cards, like crackling noises or pops from your sound card, then it's fine.

Hope that settles your confusion!