tiggerlasv at
aim.com wrote:
On Feb-21-08 at
16:05:45, Jerome Fine wrote:
If my memory serves me correctly (which is not
very
frequent these days), I seem to remember receiving
a BA23 box with an M8189 in the top slot and the
RLV11 in to next 2 slots. The memory for the system
(normal PDP-11 Qbus memory) was in slot 4.
It's entirely possible that it would work correctly.
Covention has always been that PMI memory immediately precedes
the CPU, and NON-PMI memory immediately follows the CPU.
Jerome Fine replies:
Your understanding of "convention" is CORRECT!!
However, although most systems adopt that convention, there can
be times when other problems require a different placement of boards.
In addition, I have seen a number of systems where the memory boards
(i.e. more than one) are separated, especially when some boards are
quad and other boards are dual. When DEC memory used to be so
expensive (1000s per MByte), 3rd party memory was often added
where there was an available slot. Quite often that was far down
in the backplane.
I've always just assumed that there was a reason
for it,
and never really questioned it, since I had no need to.
Necessity is often a reason to try and see if it works.
I'm surprised anyone would bother with an RLV11 in
a BA23,
since the RLV12 was readily available at the time, and supports 22-bit.
Much less space, power, and heat.
And this particular fellow was a tech support, so I am sure that he did
have an RLV12 around - but for some reason used the RLV11.
Although sometimes you just have to work with what is
at-hand. ;-)
YES!!
Sincerely yours,
Jerome Fine
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