Multi-platform distribution format (Was: Backups [was

Johnny Billquist bqt at
Mon Sep 21 20:58:26 CDT 2015

On 2015-09-21 23:26, Jerome H. Fine wrote:
>  >Jay Jaeger wrote:
>>> On 9/21/2015 11:34 AM, Paul Koning wrote:
>>> 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.
>>> 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.
>> Acch.  Bad memory cells.  This actually was discussed back in 2002.
>> Some of the correspondents in that discussion are also denizens of this
>> mailing list, may recall I made the same mistake back then:
>> The diagnostic was/is:
>> So, just to verify, I fired up my 11/23 (which hasn't been on in YEARS),
>> which came right up, and inserted the floppy and booted it:
>> It formats:
>> RD51, RD52, RD53 on an RQDX1 or RQDX2
>> RD51, RD52, RD53, RD54, RD31, RD32, RX33 on an RQDDX2
>> Sorry for the confusion.
>> JRJ
> Then you have answered the question!!
> But it there may be some possible confusion.  If I remember
> correctly, the RQDX3 was used with the RD54 and RX33
> and the RQDX2 or RQDX3 was used with the RD53.
> I could be wrong, but that is what I seem to remember.
> So on a PDP-11 Qbus system, it is not possible to FORMAT the
> RX50 which uses an RQDX1, RQDX2 or an RQDX3.
> BUT, how is it possible to FORMAT the 5 1/4" RX33  HD floppy
> which uses an RQDX3 controller?
> If it can be dome with the RX33, why not with the RX50?

Good question. I don't know why, but it is correct, as far as I know. 
The RQDX3 can format an RX33. Since the RX33 can be formatted for either 
single density or double density, and for that floppy this actually 
means it needs to be reformatted, the RQDX3 supports doing that. So I 
guess the microcode in the RQDX3 just simply detects the RX50 and 
refuses to do the operations required to do formatting there.


Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

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