Latency

DallasStar · Jul 16, 2002, 02:13 AM

For PCI Latency, would it be better to have a higher latency or a shorter latency? I'm currently at 32, but thinking about going to 64 or 128. How will that increase/decrease performance? I've heard that this can lead to a 15% performance increase and I've also heard that this can give a performance decrease, so I'm just confused now.

shuki · Jul 16, 2002, 03:52 AM

64 will give an increase in performance. will not hurt anything to try. set it to 64 and run it a few days. do some sandra bences. play some games. no stutters or lock ups and you're good to go!

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.

taken from page 8 of this guide http://www.hardwareheaven.com/thread.php?id=1864

~~Sourcer_2002~~ · Jul 16, 2002, 07:57 AM

how do i change it is it the bios or only certain cards?

shuki · Jul 16, 2002, 08:44 AM

if you have it, it's in the BIOS. has nothing to do with the card, this one is 100% BIOS.

JavaFox · Jul 19, 2002, 06:55 PM

Latency is a delay. As such, I cannot think of any situation in which a higher latency would be beneficial.

DallasStar · Jul 19, 2002, 07:01 PM

Well, I changed my latency from 32 to 128 and gained around 3-5 fps in all games. Lowered it to 64 and fps were still 3-5 fps higher than latency of 32, so I left it at 64. That's the best ratio of low-latency/performance for my pc i guess.

Jul 16, 2002, 02:13 AM	#1
DallasStar Junior Join Date: May 2002 Location: Wave Existence Posts: 2,065 Rep Power: 0	Latency For PCI Latency, would it be better to have a higher latency or a shorter latency? I'm currently at 32, but thinking about going to 64 or 128. How will that increase/decrease performance? I've heard that this can lead to a 15% performance increase and I've also heard that this can give a performance decrease, so I'm just confused now. __________________ "A picture of my existence... would show a useless wooden stake covered in snow... stuck loosely at a slant in the ground in a ploughed field on the edge of a vast open plain on a dark winter night." --- Franz Kafka

Jul 19, 2002, 07:01 PM	Thread Starter #6
DallasStar Junior Join Date: May 2002 Location: Wave Existence Posts: 2,065 Rep Power: 0	Well, I changed my latency from 32 to 128 and gained around 3-5 fps in all games. Lowered it to 64 and fps were still 3-5 fps higher than latency of 32, so I left it at 64. That's the best ratio of low-latency/performance for my pc i guess. __________________ "A picture of my existence... would show a useless wooden stake covered in snow... stuck loosely at a slant in the ground in a ploughed field on the edge of a vast open plain on a dark winter night." --- Franz Kafka

Jul 16, 2002, 03:52 AM	#2
shuki DriverHeaven Senior Member Join Date: May 2002 Location: in the hidden place Posts: 1,975 Rep Power: 0	64 will give an increase in performance. will not hurt anything to try. set it to 64 and run it a few days. do some sandra bences. play some games. no stutters or lock ups and you're good to go! 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. taken from page 8 of this guide http://www.hardwareheaven.com/thread.php?id=1864

Jul 16, 2002, 07:57 AM	#3
~~Sourcer_2002~~ BANNED Join Date: Jul 2002 Location: Indiana , USA Posts: 2,677 Rep Power: 0	how do i change it is it the bios or only certain cards?

Jul 16, 2002, 08:44 AM	#4
shuki DriverHeaven Senior Member Join Date: May 2002 Location: in the hidden place Posts: 1,975 Rep Power: 0	if you have it, it's in the BIOS. has nothing to do with the card, this one is 100% BIOS.

Jul 19, 2002, 06:55 PM	#5
JavaFox E Pluribus Unum Join Date: May 2002 Posts: 3,203 Rep Power: 0	Latency is a delay. As such, I cannot think of any situation in which a higher latency would be beneficial.