4 ms·

Oh I have a great anecdote about my Sharp MZ-700. I got into the habit of loading up games then entering the debug console and poking in random points in memor

by zandorg 17y ago

Oh I have a great anecdote about my Sharp MZ-700. I got into the habit of loading up games then entering the debug console and poking in random points in memory. As they say: It's ROM, you can't break it! But I broke it! I rebooted and found the caps lock in the debug console was broken (but did still work in BASIC). caps lock never worked again in the debug console. I think it's pretty bizarre to accidentally rewrite a ROM chip, but amusing too.

jgrahamc 17y ago
When you say "Caps Lock" are you referring to the ALPHA key? I don't recall there being a Caps Lock on that machine. Of course, it's entirely possible that writing to the ROM was decoded separately and used for some control signals. The Apple ][ I believe did some interesting address decoding to get control signals from the address bus. Looking at the memory map for the MZ-700 it appears that it implemented bank switching so that the ROM could be paged in or out and replaced with the video RAM and I/O ports. Some of those I/O ports are connected to the keyboard. http://www.sharpmz.org/mz-700/coremain.htm#banksw http://www.sharpmz.org/mz-700/coremain.htm#banksw