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First post, by maximus

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I've playing around with different PS/2 mice lately, some mechanical, some optical. I typically adjust the PS/2 polling rate for mice to 200 Hz, through Control Panel on Windows XP or using PS2Rate Plus on Windows 98 SE. Most mice work great at this setting. However, some of the older mechanical mice feel very sluggish at 200 Hz. The cursor moves slowly, as if the sensitivity is set too low. When I adjust the polling rate down to 100 Hz or 80 Hz, the cursor becomes much more responsive at the cost of some lost precision.

Why is this?

It's not like I'm filming the mouse at a high frame rate and then playing the footage back at normal speed. Everything here is real time; more samples per second shouldn't slow things down... right?

Is there a way to compensate for this effect, aside from increasing mouse sensitivity in Windows and games?

PCGames9505

Reply 1 of 2, by mkarcher

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Your understanding of the issue seems completely correct. As you describe it, the older mechanical mice are not operating properly at a sample rate of 200 Hz. There are many conceivable technical reasons for the mouse to malfunction (at least in a pronounced way) at 200 Hz. The first one that comes to my mind is a a design where the processor of the mouse can not send data to the computer and observe the rotary encoders at the same time. So everytime the mouse sends data to the computer, it stops responding to motion. Of course, the more time the mouse spends communicating, the more signals of the rotary encoders get lost.

I suggest you to just accept that some mice are obviously incompatible with working at 200 Hz, and you either throw them out or use them at a rate they work properly.

Reply 2 of 2, by maximus

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mkarcher wrote on 2020-10-24, 20:08:

The first one that comes to my mind is a a design where the processor of the mouse can not send data to the computer and observe the rotary encoders at the same time. So everytime the mouse sends data to the computer, it stops responding to motion.

Interesting idea! I bet that 's it, actually. That tracks with the older mice having issues; older, slower microcontrolers can't handle all the polling. Thanks for sharing that insight!

As far as fixing the problem, I was mainly just curious. I like to use PS/2 optical mice, or PS/2 compatible USB optical mice with converters. Cleaning the little rollers in mechanical mice gets real old real fast! I just dug up a couple of mechanicals and thought "Oh yeah, these are things that exist. Wonder what they can do?" It's kinda neat to see how they engineered around the problem of not having access to cheap, reliable optical sensors.

100 Hz seems to be the sweet spot for the older mice. Fast enough to outpace my 85 Hz CRT, and a tiny sensitivity bump in Windows and games make them feel natural.

PCGames9505