Multi-platform distribution format (Was: Backups [was

Johnny Billquist bqt at
Mon Sep 21 20:29:03 CDT 2015

On 2015-09-21 19:20, Paul Koning wrote:
>> On Sep 21, 2015, at 12:47 PM, Johnny Billquist <bqt at> wrote:
>> ...
>>> 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.
> Way more primitive is a polite way of putting it.  Just like all other PRO controllers DEC ever built, it uses programmed I/O.  The curious thing is that the PRO bus actually appears to support DMA, but it was never used, not even for the hard drive or network interface.  All those devices do I/O to on-card memory, and then the driver has to move it to/from host memory.

DECs various decisions related to the PRO are probably a mystery to all.

> I haven't tried this, but the PRO technical manual (on Bitsavers) shows that (a) there is no way to do formatting, but (b) you can configure the controller to accept, for reading but not writing, various non-RX50 formats.

Interesting. I haven't even tried digging that deep into the 
documentation. If I ever found the drivers for the hardisk and floppy 
for P/OS I could possibly consider trying to build something more purely 
RSX-like, but I doubt that will happen.


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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