27 Apr
2015
27 Apr
'15
12:54 a.m.
Josh,
I read your post again, couldn't stop my thoughts spinning.
The bootstrap ROM doesn't seem to be executing
properly, however. After
power-on or a BOOT/CTRL It'll run for a fraction of a second and then
halt, leaving me at address 0 with 161721 displayed. ROM Data appears
at the expected addresses (773000-773777, 765000-765777) but I don't
know if it's at all correct.
Display of 161721 looks evil to me: it could be a
"165721" (a valid ROM
address) with a failing bit 4000 = bit #11.
Theory: the CPU has a defective data or address line. (The bus drivers
are the usual suspects).
To test you have to read the ROM with CPU code, not over the KY11
console. You'll have to write a short assember program which copies
165000 etc to RAM 1000 or so. Then verify the copy with KY11.
If RAM == ROM, my theory is wrong.
Of course it may happen that your copy loop will not run at all because
of a cpu defect.
So best you develop and test this program with PDP11GUI and an attached
SimH before, see PDP11GUI tutorial. But keep in mind that the SimH
machines do not have 165000 implemented.
Joerg