31 Dec
2005
31 Dec
'05
6:41 p.m.
Doesn't the console ODT for the KDF11 (11/23) normally operate in 18b
address mode?
So if you exam/dep address 173000 from the console, it is the 18b
address 173000
(ie, not extended to 773000). If you want to exam/dep the boot PROM
address 773000
you have to enter that address.
Of course when the PDP-11 executes code with mem mgt off, the 16b
address 173000
will be extended to the 18b address 773000, mapping the upper 4KW of the
PDP-11
16b address space to the last 4KW of physical unibus 18b address space.
Patrick Finnegan wrote:
Charles declared on Saturday 31 December 2005 20:32:
When I examine memory at 173000 it's all
1's (177777) but I can
deposit and read data correctly into locations there. Shouldn't
the bootstrap program be copying its code there?
No. Because of 16-bit addressing vs 18-bit addressing, what the ODT
shows at 173000 is really "memory"/IO address 773000.
Again, if the
HALT line is being set for some reason, then the copy operation
can't take place... is that where I should be looking or am I
following a false trail?
There's no copy, reading from address 173000 gets translated by the MMU
to 773000 automagically.
Pat