IMSAI Progress

From: Chuck McManis <>
Date: Thu Jul 22 18:46:16 1999

ZMON in the 4FDC and later 16FDC were very Z80 in that they use the funky
bulk input instruction (INIR?) to read tracks from disk. They also swap
register sets in lieu of using a stack. Both worthless on the 8080A. The
monitor was extremely simple (even simpler than the 2K z80 monitor I wrote)
the only interesting bit was that it could read/write a track on the disk
and manipulate bits in memory. I used it to bootstrap my Cromemco BIOS by
having ZMON write the "media" type byte on the disk and then after loading
CP/M doing a SAVE and having the rest of the system installed.


At 07:30 PM 7/22/99 -0400, you wrote:
>Well, I gave up on the MIO for a while. Tony's explanation,
>while good, was making my head spin! Also, I don't have any
>26 pin card edge connectors. So I started looking at the
>Cromemco 4FDC documentation and, lo-and-behold, it has a
>serial port. The documentation on the serial port is clear
>and simple, and I now have toggled in a short program to
>initialize it and echo characters (also, put them on the
>front panel lights). According to the docs, the EPROM on this
>board contains a monitor which operates through the serial
>port, but, and it is quite emphatic about this, it is Z80
>code. Is anybody out there using one of these? With an
>8080A? Maybe could send me an alternate monitor to burn
>on an EPROM?
>Bill Sudbrink
Received on Thu Jul 22 1999 - 18:46:16 BST

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