On Jun 5, 22:41, Peter Turnbull wrote:
> On Jun 5, 17:31, vance_at_neurotica.com wrote:
> >
> > And what do you do if you want to use a QQQQ-only processor in a
QQCD
> > backplane? Put it in the QQQQ-end?
>
> I've never heard of a QQQQ-only processor. Do you have one in mind?
OK, so I've just thought of one that might be. An early 11/03
quad-height M7264 was meant for a Q-Q H9270 backplane and presumably
that's what Sridhar is thinking of. However, I don't think it's what
he calls a QQQQ-only processor.
I'd have to look at the print set or a board to be sure, but IIRC the
M7264 actually has Q-Bus on its A&B slots, so it would be OK in a Q-CD
backplane, so long as the module underneath it didn't use the upper
contacts on its own C&D slots (C and D aren't bussed; the lower
contacts on C&D are only connected to the upper contacts of the slot
below).
However, just before I hit "send", Sridhar told me what he *was*
thinking of:
> Yeah. DECsystem 5500. (MIPSFAIR-2) Chuch McManis told me it's
> QQQQ-only. It normally fits into a BA430 which is a BA440 with no
> PELE stuff in it. It uses out-of-band signaling (on ribbon cables)
> for RAM.
The short answer is "I don't know". FWIW, here are my thoughts. I
would be amazed if it put any signal(s) on the relevant pin(s) on
*both* the A&B and C&D slots (because that would lead to multiple
signal paths). I'd be rather surprised if it put some on A&B and some
on C&D, but if it did, or if it put QBus signals on C&D, it would
definitely have to go in the first Q-Q row. Or maybe the second,
something I saw about it suggests an I/O module is supposed to go in
front of it, and then the argument applies to the I/O module, really.
However, the logical way to build such a board would be with the QBus
signals on A&B, like I believe the M7264 does -- unless the bus length
is critical, and it needs the shortest path between the first and
second rows, which is the C&D slots. But would it physically fit any
other backplane than its own? Don't those new-fangled things have
different handles to anything that fits a Q-CD backplane?
Chuck?
--
Pete Peter Turnbull
Network Manager
University of York
Received on Thu Jun 05 2003 - 18:08:00 BST