Xerox Alto on eBay

Noel Chiappa jnc at
Thu Apr 14 12:48:56 CDT 2016

    > From: Josh Dersch

    > we copy disk images to/from the PDP-11/44 over 3Mbit Ethernet to the
    > Alto :).

Ah, got it. In the context of the thread, with all the RK05 discussion, I
wrongly assumed that somehow there was an RK05 involved.

    > wrote a rough implementation of PUP BSP and the Alto CopyDisk protocol
    > on top of all of that. It was fun!

I can imagine! You must be the first person in about 30 years to do a PUP
implementation! :-)

    > From: Jerry Weiss

    > Not only that, but we used Diablo Drives on RK05 Controllers. 

That doesn't surprise me one bit - the RK11-C was designed to drive Diablo
drives, and the controller/drive interface was kept almost identical in the
RK11-D (the only difference being the drive select stuff).

But the drive (either RK05 or Diablo) only provides a bit stream and sector
pulses over that interface, so turning that bit string into a sector is
controller-specific, and it would have been somewhat astonishing if the
PDP-11 and Alto interfaces had used a compatible low-level format. And, as
Josh indicated, in fact, they did not.


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