29 Nov
2016
29 Nov
'16
1:04 p.m.
On Mon, Nov 28, 2016 at 10:05 PM, Tony Duell <ard.p850ug1 at gmail.com> wrote:
My guess is that EPROMs of that time were not fast
enough for the 8X305 to
run
flat out. Bipolar PROMs were too expensive in the capacity needed. So
they copied the code into (fast enough) SRAM at startup.
AFAIK, at the time the IRMA II was made, 2K*8 fast(ish) bipolar PROMs were
not much different in price from the 2K*8 static RAMs they used. I think
the purpose most likely was to allow choice of different firmware at
runtime, either for different feature sets, or for diagnostics.