🚀 go-pugleaf

In article <1991Mar21.225509.10052@massey.ac.nz>, G.Moretti@massey.ac.nz (Giovanni Moretti) writes:
>>> WHY DO MY ALT / CTRL / SHIFT keys "appear" to get stuck?
> 
> When I type fast on my PC periodically the keyboard seems to freeze
> and it appears as though the PC has died - this annoyed me for about
> a year.  
> 
> Slowly the realization dawned that the PC itself hadn't died but the
> keyboard had (?) and this eventually got modified into realizing that
> the keyboard wasn't dead but the PC (or keyboard) thought that one of
> the CTRL/ALT/SHIFT keys was still depressed (ie stuck down) when it
> wasn't.
> 
> As I remember, the problem occurs only when I type fast.
> 
> [solution: strike the CTRL, ALT, LEFT SHIFT and RIGHT SHIFT keys]
>
> What (If anything) can I do about this?  

This was a common problem back in the days of the M24, with both keyboards
(type 1, PC-like, and type 2, an "Olivette special" with F1 to F18 keys...).
I had to dissasemble the keyboard driver (there was a conflict between
WP 3.2 key assignments and the DOS 2.11 swiss-french driver), and I looked
into this problem also.  It turned out that it was purely hardware.  Whenever
three keys were depressed at once, and with some keys even only two, the
keyboard would generate additional scan-codes (not randomly but unpredictable).
There was talk at the time to use one of the "extra" keys of the "type 2"
keyboard (CLEAR or HELP) to resotre the shift-states.
BTW: it remains a mystery why the "legal" key-combinations worked...

If you ran into the same problem, there is nothing to do.  Whenever you type
fast, you will depress the next key while (or even just before) you release
the previous, and you'll end up with "random" scan-codes.  If the code means
"CTRL-depress", the driver will wait for a "CTRL-release" code to get out
of "CTRL-state".

I used the same solution you did (I learned to depress quickly each of the
shift keys).  You could also write a small TSR to clean the shift-state
whenever you type a given key or a key combination, but is it worth the
effort?

Finally, you should try different, more robust keyboards.  I switched to a
IBM AT, and later to a HP Vectra, and never run into this again.

Hope this helps,

Markus Fischer, Dpt of Anthropology, Geneva CH