7 Sep
2016
7 Sep
'16
4:37 p.m.
On Wed, Sep 7, 2016 at 3:59 PM, Pete Turnbull <pete at dunnington.plus.com> wrote:
Yes, it has a lot of ROM sockets: it's a bootstrap/terminator/LTC card. In
fact it's the archetypal bootstrap card, the one that first had the paging
mechanisms all the others use. The problem is none of the sockets support
large ROMs, so there's a lot of fiddling to do to get a microPDP-11
bootstrap and diagnostics in there. You have to split each ROM into four
devices, so eight in total. I'm well aware of how BBS7 works, but that's
not the issue. Unless the BDV11 is modified, it doesn't work correctly in a
22-bit system as it has 18-bit termination. Although DEC listed the BDV11
(Rev.F only) as compatible they classed 22-bit 11/73 systems using a BDV11
of any sort as "not field serviceable" and wouldn't supply or support any
that way.
http://www.bitsavers.org/pdf/dec/qbus/oemMicronotes.pdf
uNOTE #004
LSI-11/73 Upgrade Paths
"NOTE
1. In the following upgrade scenarios, the systems have been labeled
as being Field Serviceable or not. A system which is Field Serviceable
has a bootstrap which meets Field Service requirements. The
requirement is that the bootstrap must execute an 11/73 cache memory
diagnostic on power-up. There is not guarantee that the overall system
will be Field Serviceable or that it will be FCC compliant."
Basically this boils down to having the MXV11-B2 Boot ROMs installed
on either an MXV11-B or MRV11-D. The MXV11-B2 Boot ROMs are apparently
not compatible with the BDV11, for reasons I don't remember 100% off
the top of my head.
Why are MRV11-D boards so expensive, at least on eBay? Were they sold
in relatively low volume compared to CPU boards?