That sort of thing was common. I never figured out why they didn't just
load the code into RAM from the ROM, then make the ROM go away. Eventually,
that was the method of choice.
Dick
-----Original Message-----
From: Allison J Parent <allisonp_at_world.std.com>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Tuesday, March 30, 1999 5:05 PM
Subject: Re: Rebirth of IMSAI
><I said 'ROM' because on a number of machines, it was just a few TTL chips
><that gated C3, lobyte, hibyte onto the data bus on the first 3 fetches
><after reset.
>
>Most used a mux and jumpers to fake a 3byte rom with the first byte
>hardwired as C3h (jmp in 8080/8085/z80) and it was jammed on the bus for
>boot and only then. another approach was to on power up map rom to loc 000
>and also F800h and then disable the mapping after the code was running up
>high. Plenty of tricks to fake that.
>
>Allison
>
Received on Wed Mar 31 1999 - 01:12:59 BST