Stripping an RA80

Tony Duell ard.p850ug1 at
Sat Jan 7 14:22:33 CST 2017

On Sat, Jan 7, 2017 at 8:08 PM, Pontus Pihlgren <pontus at> wrote:
> On Sat, Jan 07, 2017 at 08:00:43PM +0000, Tony Duell wrote:
>> The RM80 is an R80 with a Massbus interface box in the stand. Or at
>> least I think it is. I've not got any technical documentation on that unit.
> I sounds like what I've got..
>> If you have one, can you tell me what the cabling between the drive and
>> Massbus interface is? And if the 'personality board' (the smaller of the
>> 2 hinged boards under the top cover) matches that in the R80 manuals.
> I can't get to it at the moment. But I'm cleaning that area in the
> comming weeks and can look.

I've just re-read the printsets...

The microprocesor boards in the R80 and RA80 printsets are different. They
have different layouts. But the circuitry looks at first glance to be much the
same. Whether this is just a revision level thing I don't know. I will look over
it more carefully. At first glace the external connectors seem to have the same

Interestingly the personallity board in the R80 printset is called the RM80
personality board. Suggesting that as I thought the RM80 is the R80 with
a Massbus interface box.

The microprocessor board includes the write data encoder and the read
data separator. There is a clock/data pair for each to the personality
board. The R80 (and thus RM80) personality board just buffers them
and sends them to the 26 way host cable. The low level format is thus
determined by the controller. I have no reason to assume that an RM80's
controller uses the same format as the VAX11/730 IDC.

The RA80 personality board has some circuitry between the clock/data
lines to the microprocessor board (and thus eventually to the heads) and
the host cables. But not that much circuitry, I've not looked at it seriously
yet (after all it's the one part I will not be using). Certainly not enough to
have a sector data buffer. So my guess is that againg the host does a lot
of the low-ish level stuff.


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