7 Jan
2009
7 Jan
'09
3:46 p.m.
Pete Turnbull (pete at dunnington.plus.com) wrote:
No, that'll be a BA11-M ...
Oopss. Sorry.
The issue is not the number of address bits, which
won't matter at all.
That's what I was hoping, but there's one thing I don't understand - the
LSI11 CPU only drives 16 address bits, but some of the option cards (e.g.
DLV11-E) and the MSV11 memory decode 18 address bits. It's not sufficient
to simply pull the upper two address bits to always be zeros or ones - the
upper two address bits have to be zeros (for the memories) when the CPU
outputs an address in the range 000000..157777, and ones (for the I/O cards)
when the CPU outputs an address from 160000..177777. It's not a difficult
problem, but where is the logic to do this? It's not on the LSI11 card,
since those extra address bits weren't even defined in the QBUS when this
card was made.
It's that your H9273 backplane is set up for an
11/23 and won't have
W2 and W3 inserted, but they need to be for a quad-height M7264 ...
Actually the BA11-N H9273 does have W2 and W3 installed - according to the
Microcomputers and Memories handbook, those are supposed to be installed if
the CPU is in slot one, and removed if there's no CPU (i.e. for an expansion
box). It doesn't actually say anything about which model CPU, but in any
case they are installed on mine. Do they need to be _removed_ for an M7264?
So is W1 (installed) for that matter, which I think controls the LTC.
Thanks,
Bob