1 Mar
2018
1 Mar
'18
4 a.m.
From: Douglas Taylor
Is there a document that describes the bank 7 memory
page and what
addresses are reserved for what?
Here's one I collated from a large number of DEC manuals:
http://ana-3.lcs.mit.edu/~jnc/tech/pdp11/UNIBUS_Registers.txt
(Ignore the name, it applies to QBUS machines too.)
bootstrap is reserved for 173000, how many words are
allowed there for
this?
Well, the space from 773000-773776 (UNIBUS and Q18 - add '17' to the front
for Q22) is used for ROMs, and is the most common; 173000 is of course the
location QBUS processors can be configured to jump to on power on. 765000-776
in also used for some (e.g. M9301's).
How do the more complicated bootstraps, e.g.
microPDP11-53, accommodate
this limitation?
Bank switching; e.g. the BDV11, KDF11-B have a 'page control register' at
777520 which says which block of ROM is mapped into the 773000 block.
Interestingly, the DEC standard ROMs for the BDV11 and KDF11-B _don't_ copy
all the contents down to real memory, and run from there - the code is
divided into 'pages', only one of which is mapped in at a time, and it's
executed from the ROM.
Noel