strange number corruption on pdp11/34
pete at dunnington.plus.com
Wed Jan 28 08:57:46 CST 2015
On 27/01/2015 19:32, Jacob Ritorto wrote:
> I'm getting all zeroes nearly any time there's supposed to be a large
> number output to my terminal. Does this sound familiar to anyone?
> This happened last night on rsx and is also happening today on xxdp.
> example xxdp testing rl02:
> BUS ADDRESS (O) 0 ?
> VECTOR (O) 0 ?
I agree with Johnny; even before I read his post I looked at this and
thought here's a simple case of GIGO :-)
XXDP makes NO assumptions about things like CSRs for devices, and does
almost no sanity checking on input. There's no rule that says a
controller has to be at a particular address, not even necessarily in
the I/O page in Bank 7. When you told XXDP the CSR is at address 0 (by
not entering a different value), that's what it would believe, and it
would happily test whatever is there. In this case, that's real,
existing, working memory, so it won't even fail with a bus error, but it
will read back zeros after it's cleared - exactly as you saw. Even the
elapsed time is genuinely zero, as it's reporting immediately, and all
the other values are the contents of a zeroed memory location instead of
The fact that your CPU boots XXDP - never mind something more demanding
like RSX or BSD - suggests it (and the memory, disks, etc) is pretty
much working. Retry the RL02 test with proper values.
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