empleat wrote: ↑24 Jul 2021, 21:21
BTW pci-e cards are not a holly grail, they usually cause huge DPC latency, just a warning!
While this is true -- PCIe may make things worse some of the time -- but not always.
For other readers:
If you're getting a PCIe card for a high-pollrate device, it's generally a good move (usually) if you've got lots of USB accessories. You want low latency jitter for a Razer Viper 8KHz. You don't want random latency effects. As long as you're using dedicated lanes to the CPU, the DPC latencies over the longer circuit lines of a PCIe lane, often tend to be more consistent when given its own uncongested PCIe lane and uncongested USB controller chip; thus outweighing DPC latency for the mouse.
So it's possible it's preferable to tolerate higher "stable" (jitter free) DPC latency in exchange for lower mouse latency jitter, if the randomized non-DPC latency is causing more problems with aimfeel. As a metaphor, consider comparing RANDOM(1-to-10) latency, versus exact 2.5 of exact perfect stable latency!? Predictable latency can sometimes be superior;
The fetishization of absolute latency neglects the random latency factors, which can also be killer too. Also, you're not necessarily moving all USB devices to PCIe -- just the mouse only or keyboard only, while keeping the other on the motherboard chipset. If you're lucky to have multiple high performance motherboard chips, you can just play port roulette until things look good latency-wise and jitter-wise (see screenshots below) -- but if you're plugging USB devices to the hilt (external disk, webcam, VR headset, etc). The onboard USB chips often leave much to be desired when you're clogging up the port... Here, the PCIe USB can be the savior here to clean up your high-pollrate.
I can even see my mouse cursor occasionally jitter if I'm sharing the USB chipset with other high-Hz devices + external USB SSD + VR headset at the same time. That's a bigger poison than a PCIe card when you've got congested ports that are simultaneously busy. And when I plug my mouse to a different host USB chipset (even if PCIe), the jitters stop. Perhaps the lag is higher, but the cursor stutter (which will also lead to mouseturn stutter in games) is the worse poison. Random USB latency so terrible, that it shows up as visible mouse jitter;
You can try vacating all your onboard ports (Razer 8KHz on motherboard, everything else on PCIe USB) but vice versa may be preferable since you have fewer events of high DPC latency since you only have 1000 to 8000 transmissions per second from a mouse over PCIe USB, instead of the millions of transmissions per second from all other PCIe lanes -- so your average DPC latency may not budge much; it's worth testing both ways. Either way, it is important to avoid USB hub congestion for your critical competition devices.
Because of all these real-world factors of clogged USB ports of many accessories,
consistency improvements happen more often than not --
provided you choose an uncongested dedicated PCIe lane + one high-Hz USB device per host USB chipset. Yes, that means you may need to play PCIe slot roulette until you find the slot that doesn't contend with any existing devices. You may burn lanes (e.g. plugging a x1 PCIe USB port card in a x4 or x8 PCIe slot) just to get what you want, but so be it. And you might even be PCIe 2.0 instead of PCIe 3.0 or 4.0, but then again, that generally isn't problematic for a low bandwidth device like a mouse, as long as pollpacing improves...
There was tests that PCIe cards massively improved Razer 8KHz mice because of sidestepping the port roulette effect (
see this thread)
viewtopic.php?t=7618
YMMV -- some USB chips on motherboards are superior to others -- but tolerating a very slightly DPC latency can be the lesser of evil compared to some really crappy chipset USB implementations -- so test both ways and see how the mouse feels;
Razer also did some internal PCIe-USB tests and found 8KHz Viper sometimes perform better when given a dedicated PCIe lane + dedicated USB controller. It may not always be true, but it may sidestep a congested USB controller, or shared PCIe lane (e.g. USB chip sharing with other devices on same lane) or bad chipset implementations.
Another thing to consider is PCIe lanes may go through the chipset instead of directly to the CPU; the implementations with direct-to-CPU PCIe lanes may perform better. But that congestion can be the lesser evil versus congested USB hub silicon (hub traffic congestion, USB processing congestion). It's all a pick-your-poison game; so don't avoid testing an unturned stone because of assumptions when USB cards are a mere $30 each!
I agree it is not a holy grail but I don't want to discourage people from trying such a cheap fix;
Chief Blur Buster wrote: ↑16 Oct 2020, 00:29
Houston, we have a problem.
Especially with 4000 Hz keyboards and 8000 Hz mice being used simultaneously.
I just helped someone solve a high-Hz USB performance interference problem between two high-Hz USB devices:
Problem: High-Hz poll performance interference between 1000 Hz keyboard + 1000 Hz mouse
MaxTendency wrote: ↑12 Oct 2020, 16:35
While I'm pretty convinced that 8k hz mouse polling is going to be not only noticeable but also impactful , I'm starting to wonder how much keyboard polling will affect this. High keyboard polling has known to destabilize the mouse polling and vice versa.
For example this is a 1khz mouse polling on an optimized setup with a 125hz keyboard.
As you can see the variance is quite little, barely 1hz.
This is the same mouse but the keyboard is wooting one set to 1k hz.
All of a sudden the variance is 20hz. Looks like windows can't even fully handle 1k hz keyboard and mouse at the same time.
With keyboards now supporting 4k hz polling like the
Corsair K100, I'm curious how will this affect the stability of 8k hz mouse polling. Seeing that a 1k hz keyboard is enough to destabilize a mouse set to just 1k hz, a 4k hz keyboard would probably trash the stability of a 8k hz mouse.
Solution: Serparate USB controllers and PCI bus lanes per 1 high-pollrate device
MaxTendency wrote: ↑15 Oct 2020, 20:58
Small update, using the asmedia port for keyboard (the lowest one, right next to the usb-c port) while using top port for mouse seems to minimize if not remove the impact of high keyboard polling on the mouse polls.
Blue is the mouse and red is the keyboard. This combo provided the best polling, pic of polling attached below.
Yeah, that was what I thought. Glad my recommendation helped!
With ultrahigh poll rates, you really need to isolate to one USB chip (and/or separate bus lanes) per high-pollrate device.
PCI-Express USB cards are also another solution that can help this. Plug the keyboard into the motherboard USB, and plug the mouse into the PCI-Express USB. Or do
do USB port roulette until you find jackpot. Keep the adjacent ports empty (port above/below a plugged-in high-Hz USB device) because they often share the same USB controller.
This would probably become a staple recommendation of the new 2020s-era "Blur Busters Mouse Guide II"
Until the motherboard manufacturers "keeps up with the Joneses" and have a dedicated-USB-chip keyboard port, and a dedicated-USB-chip mouse port for the 2020-2030s esports era of 4000 Hz keyboard + 8000 Hz mouse + >360 Hz monitors + RTX 3080+ framerates.
This Grand gaming computer upgrade supercycle is going to be very interesting. I rarely see so many concurrent upgrades happen. Those now seem to happen only once every 5-10 years, rather than every 2-3 years in the 1990s-2000s. We are seeing a major
Vicious Cycle Effect tick-tock (multiple concurrent frequency upgrades).