Some pointers needed on a 11/70

From: Pete Turnbull <>
Date: Wed Jan 2 18:19:06 2002

On Jan 2, 21:08, <> wrote:

> Besides some small mistakes (not all PS modules in place for the CPU, and
> not having a powered memory box), we managed to get the machine partly
> running, that is, the lights are reacting to the 2 knob settings, and
> data is displayed on the console.
> However, when depositing some data at address 1000, nothing happens, and
> the parity and/or address error light goes on. Same when trying to see
> the contents of any (low) address. So, I have a few questions:

I'm sure there must be people on the list who know more about 11/70s than I
do, but since no-one else has replied yet...

Is the memory powered up and connected? At the right address (you must
have some memory in the lowest 28KW to start up)? Is the cache working?
 There are various things done by the power-up bootstrap diagnostic
routines to set up the cache and memory system; and there are ways to
disable cache, Unibus map, certain errors, etc, by poking bits into control
registers. And I think you probably want to set the console Address Select
Switch to CONS(ole) PHYS(ical).

> - I have heard about a system address register which sets the size of
> the memory, where is this address located?

17177760 is the "lower size register". Set it to the address of the last
addressable block of 32 words (ie offset by 6 bits). There's an upper size
register as well, "reserved for future use", read-only, reads as zeros, at

> - At the back of the memory box, there are somw switches and 4 thumbwheel
> switches. What is their purpose?

I assume to set the base address of the memory in the box, but never having
set one up, I don't know.

> - Is the ROM boot address still 177560? or must it be 17777560 on the

Well, it would be 18 bits, since it's on the Unibus, in an M9301-YC or
equivalent. But 177560 (or 777560) is the address of the console serial
line. The bootstrap is at 765000. I'm not sure if you need to set the top
four bits as well, as if I recall correctly, the Unibus is mapped to the
top of physical memory.

Pete						Peter Turnbull
						Network Manager
						University of York
Received on Wed Jan 02 2002 - 18:19:06 GMT

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