Multi-platform distribution format (Was: Backups [was

Johnny Billquist bqt at
Mon Sep 21 11:47:02 CDT 2015

On 2015-09-21 18:34, Paul Koning wrote:
>> On Sep 21, 2015, at 12:28 PM, Jay Jaeger <cube1 at> wrote:
>> On 9/21/2015 4:30 AM, Johnny Billquist wrote:
>>> On 2015-09-21 02:11, Jerome H. Fine wrote:
>>>>> Chuck Guzis wrote:
>>>> Note that the RX50 was the same.  DEC finally changed
>>>> their marketing policy with the RX33 drive which used the
>>>> same 3.5" HD floppy media as the PC.  It was actually
>>>> possible to FORMAT those floppies under RT-11.
>>> No, DEC actually did support users formatting RX50 floppies on their
>>> own, but only on the Rainbow.
>>>     Johnny
>> There was also a standalone PDP-11 diagnostic program available that
>> could do it.
> For RX50?  On standard PDP11s, those used an MSCP controller, which means the controller would have to do it.  Did it?  The only MSCP controller I remember that did formatting was the UDA50.

For Unibus, the controller would be the RUX50. MSCP, as you say. And I 
suspect that one didn't do formatting.

For Qbus, it would be the RQDX, which was MSCP, and did both the RD 
disks and RX50. I'm not sure, but I think the RQDX could perform some 
sort of low level formatting for the RD anyway. Not sure what it would 
say if you pointed it at the RX...

> I suppose you could on a Pro, since that had its own particularly disgusting junk controller.  But I haven't seen RX50 formatting there.  My impression was that they came factory formatted, with the DEC-specific 10 sector per track format.

Ugh! The PRO controller probably was weird enough to not allow you, even 
though as far as I understand, it was also way more primitive than MSCP.


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