I checked in a program the HID variables for the mouse and trackpad are the same X-Axis Y-Axis. But 'chuck' probably just calls some interface that is available on the OS. That is how it works on Mac OS X. So if the OS admits PS/2 devices, then should feed some information into that interface, which is what 'chuck' then reports.
Yes, that's basically what I imagined was going on as well.
Though some older protocols like SCSI have advantages over more modern, consumer friendly ones like USB, I don't there are any system bus issues for these, as one has some intermediate hardware that provides the communication. In the 1970s I assembled a computer, that wrote the keyboard characters directly into memory, which the CPU checked in a loop. This is highly inefficient way to handle it.
Ah, yes, I would indeed imagine that would be fast. For all I know that's what Apple is doing now... Having full control over the hardware specs would allow you to do that. The only downside that I can see would be that spilling drinks in the keyboard might cause the memory itself to be fried but I suppose you might be able to have some sort of protection against that.
This might also be limited by factors like maximum poll-rate and resolution;
For the USB keyboards I have checked, this seems to be limitation of the keyboard, that is, even before the data is sent to the computer. This is because it differs with the keyboard. The computer is so fast that it easily can handle any human typed key roll-over. The slow USB 1 bus is on about 12 Mb/s, which should admit for tens of thousands of key stroke in a tenth of a second.
I meant PS/2 might be limited there. In recent years the quality of high performance mice has gone up quite a bit, probably originally inspired by games like Quake. It was chiefly mouse signals that I was refering to. Sadly (I feel) the quality of keyboards hasn't made the same progression and keyboard ghosting is now typically worse then it was on keyboards from the 80's.
When experimenting with the diatonic key map, the problem is mostly due to other process running. One notorious one is looking for RSS feeds.
Yes, I was a bit disappointed when I found out about that as well though I do think that's a quite different issue.
I think I tried a Mac keyboard once on a Windows, finding it not working. One needs to have a driver installed. Each device may require its own. The USB HID interface unifies those, so that only one driver is needed, which then can be supplied by the OS. The latest version of this USB HID interface or standard was issued this year. So perhaps it was not available when 'chuck' was written.
Odd. I've never seen a keyboard not work, I think. Special keys (like volume or "sleep" ones) may need a driver in my experience but the keyboard itself always worked. I think you can even take a ps/2 keyboard, use a USB adapter and plug it straight into a Mac, provided you are willing to remap some stuff to the "Apple" and related keys.