26 Jul
2006
26 Jul
'06
5:12 p.m.
Julian Wolfe wrote:
Just as the subject says, I'd really like to know,
are M9312 boot prom
images compatible with M9301?
Not directly. The way the image is partitioned
between proms is
different: M9301 spreads a word across 4 proms, M9312 places a word in 4
successive nibbles of the same prom. Another issue is the way that the
boot switch is handled. Both boards place an address on the UNIBUS when
they detect a power fail restart vector fetch caused by the boot switch,
but the way this address is stored in the proms is different and the
allowable addresses are different.
I built an adapter for the M9301 that lets me use two 8 bit eproms in
place of the four 4 bit proms. I have some random notes about it here:
http://www.chd.dyndns.org/pdp11/Notes/M9301.shtml
http://www.chd.dyndns.org/pdp11/Notes/boot_board.shtml
-chuck