Wandering Thoughts archives

My discovery that the USB mouse polling rate matters

I mentioned recently that I had found a PS/2 to USB converter that worked for my keyboard, but it made my PS/2 mouse kind of jerky and stuttery. Over the past few days I've discovered why that is so, which is unfortunately kind of bad news for me with this converter.

As you might have guessed from my sudden interest in Linux's mouse polling rate, my problem turns out to be that a PS/2 mouse that's run through the PS/2 to USB converter does not have a high enough polling rate. Courtesy of evhz, I can put actual numbers on this for all of the mice I have handy. With default settings for mouse polling, my scroll wheel mouse runs at 125 Hz, my PS/2 mouse claims a 90 Hz rate when connected to the PS/2 mouse port, and for the PS/2 to USB converter I get a rate that jumps back and forth between 31 Hz and 41 Hz. Increasing Linux's mouse polling to 500 Hz increases the rate of real USB mice to that, but it doesn't really change the performance of the PS/2 to USB converter; evhz still has it at an average of about 36 Hz.

This, it turns out, is nowhere near as fast as it needs to be in order to be really smooth. A 36 Hz average rate is just good enough that the mouse mostly performs reasonably well; it's not obviously terrible or anything. Instead it's just subtly jerky from time to time. I could almost imagine it or persuade myself that it wasn't there (and I did off and on). But it's not good enough.

The bad news is that this is clearly an issue in the PS/2 to USB converter itself. Linux can ask it to run at whatever high rate I want, but the converter simply doesn't pass on mouse motion that fast or frequently. I'm never going to have a satisfactory mouse experience with this converter, although it's been fine for my keyboard. The good news is that I clearly don't need a special fast USB mouse in order to get the responsiveness I'm used to, at least if evhz is correct about my PS/2 mouse running at 90 Hz natively.

(According to this PS/2 mouse reference (also), PS/2 mice do natively run at 100 Hz by default unless the host changes that. Linux probably doesn't.)

This leaves me with a number of ways forward. First, I can try other PS/2 to USB converters purely for their mouse conversion, to see if they run at higher sample rates. Second, I'm trying out a HP three button optical USB mouse. So far it seems okay but perhaps not as smooth as my PS/2 mouse, which may partly be because it's an optical mouse instead of a ball mouse and I'm using it on a fairly featureless surface. All of this is enough options that I'm not really worried about things any more; mostly I'm just going to use my PS/2 mice until I don't have a PS/2 port to plug them into.

(Getting a Contour Mouse remains kind of tempting, though. If I liked it, it would be great. That 'if' is of course the problem, given their price.)

How my PS/2 to USB conversion issues have shaken out

In this entry, I covered my problems with trying to find a good PS/2 to USB converter so that I could keep using my favorite keyboard and mice. Since then I have more or less come up with a solution, although it's not a complete one.

Based on Chris Wage's recommendation, we got a PS/2 to USB converter that's specifically beloved by the IBM Model M fans. Specifically, the ZioTek 'PS2 Keyboard & Mouse to USB Adapter'; here is its Amazon listing (which is where we got it). This appears to do an excellent job of converting PS/2 keyboards to USB; I used it for several days on my office machine without noticing anything different or experiencing any problems. Unfortunately it's not as good with my PS/2 mouse. Oh, the mouse works, but it's kind of jerky and stuttery compared to the smooth pointer movement I get through the PS/2 port. The result is usable but not pleasant. Fortunately the ZioTek converter can be used with the keyboard alone.

(As always, one never knows if these things are going to stay in production and remain unchanged over the long term. Since this model's cheap, I intend to buy several so I have spares.)

This is not an ideal situation, of course, but I have at least three options. First, now I only really need a single PS/2 port on any new machines, for the mouse (although I'd still like two). Second, I can try to find a PS/2 to USB converter that handles the mouse smoothly even if it mangles keyboard input and just use it for my mouse. And third, I can explore USB mice, either the Contour Mouse or (as suggested by a commentator here) a mouse with a side thumb button that I can repurpose as the middle mouse button. And who knows; by the time I exhaust the first two options, perhaps someone will be making a genuine three button USB mouse.

(The tempting crazy option is to sail off into the uncertain waters of mechanical USB keyboards, or even that and a Contour Mouse. In a way, it feels like I have computer chair reluctance here; it's quite possible that the results would be clearly better than my current setup.)

PS: The one thing I haven't tested is how well the ZioTek converter works in the BIOS during early boot (apparently some USB keyboards and converters have issues here). On the other hand, Amazon reviewers seem to have had this work.

Do generic stock servers have a future in a cloud world?

One of the things I've been reading lately is a certain amount of PR about 'the cloud' and about how most everyone with a good sized private datacenter will wind up moving to the cloud instead because they just can't compete with the economics. I don't know enough here to have an opinion, but the people here seem to make a plausible case (both about how much more efficiently Amazon can operate their servers than you can operate yours and how hard it'd be to match all of their management tools with your own software). Given that this future might come to pass, I got to wondering: what happens to stock servers?

The people running Amazon and Google and Facebook and so on are not buying off the rack Dell/HP/Lenovo/etc servers; one of the reasons they can be more efficient than you is that they use custom designs that are adapted to their exact environment. Instead, the people buying those servers in bulk are exactly the big datacenters that are supposed to move to the cloud. Currently, all of the rest of us smaller people buying servers have very likely been benefiting from the volume of big datacenters, since high product volume drives down prices and pays off custom engineering and so on; selling tons of generic 1U servers has to be part of why they've become relatively inexpensive. But what happens to the generic stock server market if that big datacenter volume goes away? As the number of people buying their own servers shrinks, will we still have inexpensive stock servers to buy?

One possible answer is that there's enough volume in the small business sector to sustain at least some of the major players and keep stock servers inexpensive and available. I don't know if I believe this, although I also have no idea how large this market segment actually is. Another potential answer is that while big datacenters in the well connected West may shrink a lot, there are plenty of places where issues like bandwidth and latency will mean that local companies (both big and small) have local servers and this will sustain the server market in general.

Or we may lose those cheap, convenient, readily available servers from companies like Dell, which would probably leave us buying more servers from smaller OEMs like SuperMicro. They would cost more, which would be a bummer, but they might not cost lots more, especially if we got 2U or 3U units instead of 1U ones. We're lucky enough to not really be rack space constrained; for everyone else, well, in the cloud-heavy future the colocation operators may drop their prices for rack space due to reduced demand.

(Before 1U servers became generic popcorn, my impression was that you paid extra for squeezing all of the necessary components into such a small space. I suspect that this is not the case today, due to the high volume.)