PCI latency? a Q for Gurus

[Feneeth of Borg]

Originally Posted by Pylor

I used this program like it said to and i started playing cs source, only the stutering was worse. The only thing i can contribute this to is that my framerate is going over my refresh rate, noticing this i decided to run stress test and i got 66.02 fps (on dx9, presi tweak), this is more than 20 fps more than i got before, did valve release a patch or is this because i lowered the latency to 64? also would the fps going over the refresh rate cause a stutering effect? i did notice a tad bit of tearing.

This is because the concept of PCI latency timers seem to be misunderstood by you, because each one is the amount of cycles the device gets until the PCI bus moves on to the next, so turning down all but the video card would end up with incredible framerates, but struggling audio and networking. Remember, Balance is the key.

[amablue]

I got PCI latency tool, but it doesn't show my video card on the list of devices. I have an nvidia 8800, but all I see on the list is my wireless adapter and a bunch of Intel stuff. Anyone know why?

[morbias]

Because PCI is not the same as PCI Express.

[ForgedReality]

Tried installing the latest version of this tool on win7 64bit, and Windows tells me it won't let the program load a driver because it isn't digitally signed.

[Feneeth of Borg]

Originally Posted by zenkmander

Leave everything alone BUT your video card. If your video card is at 248 or around there, for example, try lowering it to 32 and applying (make sure you click Save and Apply on Startup, etc). If 32 doesn't perform well, up it to 64 or 128.

Sorry but you are incorrect, its not like ram latencies in which its simply lag. If you turn down the agp controller your performance will decrease, period. Don't make claims that its helping if you don't have proof or even logic to defend your claims, look at the pci bus page on wikipedia, and my performance agrees with it, 248 worked the best for my radeon 9800 and my 2600 (agp).

There is another way to improve performance, by disabling unused devices, ide controllers, usb controllers, card readers, modems, etc, go into device manger and select "view by connection" disable pretty much everything that doesn't have anything connected to it. On my laptop, I reduced the devices fighting for bandwidth form 17 to only 12, considerable gains in networking, graphics, even my mouse was higher framerate.

Most sound cards can handle 32, I suggest 64 for network adapters, and 248 for agp bus. There is a reason its set this way from the start, and its not because its the most stable.

[VisitorX]

hi i have a question which settings is good for me with an nvidia 9800 gtx + ??

[killerxr290]

lol

PCI-E cards dont have any latency timers. So you cant change your PCIE latency, PCI you can but your video card is PCIE so it would be pointless

[VisitorX]

Thanks for answer...

for what i have the settings in bios menu.. i changed it to 128 and now 3d applications run a lil better..

it meens equal which settings i do its pointless ??

[deltatux]

Originally Posted by killerxr290

lol

PCI-E cards dont have any latency timers. So you cant change your PCIE latency, PCI you can but your video card is PCIE so it would be pointless

Originally Posted by VisitorX

Thanks for answer...

for what i have the settings in bios menu.. i changed it to 128 and now 3d applications run a lil better..

it meens equal which settings i do its pointless ??

PCI latency is basically just how much time you allow the PCI bus controller to allow each device to master the bus. Since the PCI bus is basically a Time-Division Multiple Access (TDMA) technology, each device gets a slice of time to the full bandwidth before it has to give up the bandwidth channel for the next device.

You don't get this with PCI Express because it's not a bus system, it's a point-to-point interconnect, all devices gets its dedicated lanes and NEVER share resources. Thus, having a latency setting is quite useless since there's nothing to share.

What VisitorX experienced is probably a placebo effect caused by the switch.

deltatux

[TruMutton_200Hz]

Originally Posted by deltatux

You don't get this with PCI Express because it's not a bus system, it's a point-to-point interconnect, all devices gets its dedicated lanes and NEVER share resources. Thus, having a latency setting is quite useless since there's nothing to share.

PCIe data transfer is packet based so latency still matters to some devices (such as graphics cards and soundcards) but not to all devices. The real reason why PCIe has no latency setting is because the system handles device priorization automatically.

[deltatux]

Originally Posted by TruMutton_200Hz

PCIe data transfer is packet based so latency still matters to some devices (such as graphics cards and soundcards) but not to all devices. The real reason why PCIe has no latency setting is because the system handles device priorization automatically.

PCIe latency in terms of packets are too small to detect to the point where a PCI latency switch would affect any device. Many devices that do require low latency works very well on the interconnect without any special tweaks to the interconnect.

This is not true with PCI since there's the whole bus mastering latency.

deltatux

[TruMutton_200Hz]

Originally Posted by deltatux

PCIe latency in terms of packets are too small to detect

Then please explain why device priorization is part of the PCIe design.

[deltatux]

Originally Posted by TruMutton_200Hz

Then please explain why device priorization is part of the PCIe design.

Personally, I have no clue, from what I've learned through reading hardware articles is that PCIe doesn't share its resources with other devices. My guess here would be because the software layer is the same as the older PCI so for software, the prioritization is required so traffic for PCIe devices that are sensitive gets priority in the software layer.

deltatux

[TruMutton_200Hz]

^ Here's the more accurate explanation:

http://arstechnica.com/old/content/2004/07/pcie.ars/5

[churlock]

Originally Posted by ForgedReality

Tried installing the latest version of this tool on win7 64bit, and Windows tells me it won't let the program load a driver because it isn't digitally signed.

This worked for me (posted by "Goodtwist" on another forum):

Simply let Windows 7 deal with the problem by pressing "Troubleshoot compatibility" in the context menu, while holding your mouse on the installation file.

What turns out to be the problem - Windows denying you to install PCI Latency Tool due to lacking admin authority - is a missing digital signature of the PCI Latency Tool Config Space Access Driver (in LtcyWDM.sys).

This advice should be posted under the instructions for the PCI Latency Timer app as a lot of people are having an issue trying to load under win 7.

[BetA]

wait, is that tool actually usefull for me? even i have pci express? or isnt it just for agp cards etc..like in the old days..
i thought nowadays u dont have to worry about this anymore..

can someone please help me out here?

-BetA-

[Mineria]

Originally Posted by BetA

wait, is that tool actually usefull for me? even i have pci express? or isnt it just for agp cards etc..like in the old days..
i thought nowadays u dont have to worry about this anymore..

can someone please help me out here?

-BetA-

Doubt that it will do anything for your system, the app is old (not updated since December 2005) so shouldn't be used on modern systems.
Also changing from default values can give sync problems, had that with some recording software in the old days, it did help with some games back then thou.

[Halmeth]

Sups all... I know this is a tremendous old thread, and a tremendous old software... But i'm already using an old computer with an old AGP card (Geforce 7800 GS AGP) My issue is the next: When I play Source (valve) Games I get that stressful issue of crash to desktop with looping sound... Maybe this PCI Latency Tool can be useful for my old-lady machine... what are the best settings to get a good perfomance gaming on CS Source or Day Of Defeat Source?...

Thanks all...