3 Sep
1998
3 Sep
'98
7:24 a.m.
The drives are Diablo 30 drives, and the disks (there
are several), are
marked PDP-11 system disk, and PDP-11 Backup disk. The previous owner
told me when I picked them up, that they should boot. Last night, I tried
playing around with it again, and tried to access the disk status
register (round about 17400(8) from memory, but I'm at work just now and
it was late last night, so my terrible memory can't be sure...). It
seemed to contain 000000 (from typing @17400/). :( Which doesn't, as far
as I can tell from the assorted docs, look to promising for the state
drive.
17400 can't be a disk address... The physical address range for I/O
page addresses is 17760000-17777776. On some machines this can be
shortened to 760000-777776, and on some, even further to 160000-177776.
(Though if you are referencing the I/O page from within a program, you
must use a 16-bit value in the range 160000-177776, and the memory
management must either be off, or setup such that the mapping registers
for that range point to the actual I/O page).
Have you examined memory beginning at 0 to see if there has been any
code actually loaded from the disk? (Deposit something like zero or
177777 in a bunch of locations beginning at address 0, and after trying
to boot, check those addresses... if they are different from what you
entered, then that might indicate the disk has actually done something)
BTW - what sort of DEC disk do your disks emulate? That would help
in being able to tell you what address you could twiddle with, and
what toggle-in boot code to try...
Megan Gentry
Former RT-11 Developer
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