View Full Version : AT2XT redux

May 10th, 2017, 11:54 AM
Finished the AT2XT adapter project; tested today with Chromedome's Model M keyboard.

Thanks to ChuckG and the others whose prior work and / or timely advice made this possible.

Chuck: noticed one program ("LUCID", a 123 clone SS) which thought the NUM lock was on when it was indicated off on the keyboard, and vice versa; no other anomalies.



May 10th, 2017, 12:19 PM
Could well be. Remember that the original XT keyboard protocol is unidirectional--that is, unlike the PS2/AT protocol, the host cannot send commands to the keyboard. Various shift states in the XT world are dictated by a byte in the BIOS RAM area, so any program can change that--and the keyboard will never know.

This wasn't a problem on the original XT, as the keyboard lacked any sort of LED indicator for shift lock/num lock state. On those third-party XT keyboards with LED indicators, it wasn't uncommon to see the LED reflecting a different state from the BIOS shift state byte.

May 14th, 2017, 12:51 AM
Could also depend on firmware.

CTRL+ScrollLock = BREAK

LEDs shouldn't toggle if you press BREAK/PAUSE or use lock keys in combination with CTRL, but they did in firmware 0.94.