Modifying a RXV21 for an 11/83
cz at alembic.crystel.com
Sun Jan 24 20:11:38 CST 2021
Ok. My guess is it throws off the cache on the 11/73 and above as it
works in an 11/23 (which is soooooo slow!).
I looked at the images, cut the traces, then soldered in two of the
wires. Board did not work on either the 11/83 or the 11/23+ CPU. However
when I looked closer I saw the tiny little wire down by the crystal and
the Q bus fingers. Put that in, and the board now works on the 11/23+,
will take the whole thing apart (again) and plug in the 11/83.
Fortunately I have the pdp11/83 configured with a Q bus memory board
(2-4mb) and a PMI memory board from an 11/84 placed in slot 2 (so the
11/83 will access it as Q Bus memory). Thus I could pull the 11/83 CPU
in slot 1 and pop the 11/23+ in. Aside from the exceptionally slower
speed and long boot times it works pretty well for testing.
Still need to get a 11/83 compatible PMI board, but the 11/84 ones work
as normal Q bus memory.
Thanks! Now I can read some of these RX02 disks and image them. I'm
guessing my BRU floppy that I generated with the RXV11 controller will
not boot on this RXV21 controller so I'll have to re-make that. And so
far it doesn't look like the disks made on that third party MXV21
controller are compatible with the RX02, should they be?
On 1/24/2021 7:41 PM, Jerry Weiss wrote:
> On 1/24/21 11:27 AM, Chris Zach via cctalk wrote:
>> So I found an RXV21 board in the pile of stuff here and popped it into
>> my 83. Crashes the system. It's an M8029 D board, and I see from this
>> site that you have to add a few traces and cut a few others to make it
>> work on an 11/73 or better.
>> I'll pop in an 11/23+ CPU just to test it, but is it really just
>> putting in two wires on the top of the board and cutting a total of
>> three traces? Looks simple enough...
> My M8029 stamped Rev F has three jumpers and three trace cuts. It
> matches the images posted in the link and works with an 11/73 ot 11/83.
> But yes, it should be that simple.
> There is a sharpied H on my card, which it is not the way DEC marked
> these boards. The available field maintenance prints refer to this (no
> G). I don't know what the change was.
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