8 Feb
2012
8 Feb
'12
3:23 p.m.
On Tue, Feb 7, 2012 at 2:14 PM, Kevin Reynolds <tpresence at hotmail.com> wrote:
The cabinet for the microvax I is different that the
BA123 and the BA23 that are available for the later vaxes I believe.
Nope. Bog-standard BA23 or BA123. There are later cabinets for
MicroVAX IIIs, but they are models like the BA213. You can take a
MicroPDP-11/23 and re-stuff it as a MicroVAX-I or a MicroVAX-II,
though you will probably need different peripherals (I don't think the
DLV11/DLV1J is supported under VMS, for example, though the RLV12 is).
The uVAX-I has a dual-board CPU that must be installed in slots 1-2 of
a backplane with CD slots, and the memory sits _on_ the Qbus, so with
22 address bits, you top out at 4MB. The later MicroVAXen fit on a
single board and use PMI memory (different boards, matched to the type
of CPU). I don't know the MicroVAX III memory max off the top of my
head (after my time), but the uVAX-II has 1MB on-board and can take,
IIRC, 12MB in the first two slots.
Besides memory, the big limitation I remember from those days about
upgrades was disk size. The uVAX-I shipped with the RQDX1 which did
not support disks over 30MB, I think. (RD52 but not RD53, IIRC). The
RQDX3 supports DEC disks up to the RD54 (154MB) and non-DEC disks,
though it can be tricky to get the Field Service formatter which can
label non-standard disks. Even so, MFM disks top out pretty low. I
think I managed to fit VMS 6.0 on an RD54 on a 9MB uVAX-II, but I had
to leave something behind (like the HELP files). Using an MSCP SCSI
controller bypasses this dance and leaves memory as the critical
resource.