Altair Emulator enhancements - progress report - questions

From: ajp166 <ajp166_at_bellatlantic.net>
Date: Tue Sep 12 13:17:07 2000

From: Dwight Elvey <elvey_at_hal.com>


> There was no standard port used for serial I/O. and even if
>there was, the device could have been a AY-3-1015, a 8251 or
>a 8250. All of these would have different handshake and
>setup information. I don't know how you'd be able to have
>anything that you'd call standard.


Wrong. The standard devices were usually AY-3-1015/COM2502
based and tended to use the MITS status bits and IO addresses.
Mits never used the 8251, and the 8250 was later to the scene.

MITS set a standard in as much as there were very few then
by sticking to the 2sio standard or the SIOB standard for serial
ports with the SIOB being a uart like ay-3-1015 and the 2sio
using 6850s.

Expereince says, the common usart like the 1015/com2502
was most widely use with the 8251(9551/2651) the 6850 running
follow on. The only S100 board I've seen the 8250 on was the CCS.
The 8250 was not a widely used part in the late 70s on S100.

I'd be quick to point out that the mits era was 1975-1977ish with
other players already emerging as new leaders (NS* horizon
and friends) by late 1977 in the S100 space. From 77-80 that
 would again undergo major changes going from the MITS/IMASI
front pannel style machines to the Northstar*, CCS, Compupro
turnkey style front pannel less and disk based systems.

It was also simple enough at the time to fix IO in most code as
it was trivial in construction and easy to find in binaries.

allison
Received on Tue Sep 12 2000 - 13:17:07 BST