[Simh] RP/RM differences in header commands (for ITS, salvager)

[Johnny Billquist]

On 2019-06-28 15:45, Paul Koning wrote:
> 
> 
>> On Jun 28, 2019, at 3:07 AM, Johnny Billquist <bqt at softjar.se> wrote:
>>
>>>  From a hardware point of view, sector header "Word 3" and "Word 4" have
>>> no particular meaning.  Just for completeness, can you point me to a
>>> reference where "pack number" is defined or used by the software?
>>
>> Search for DEC standard 144. If nothing else, I think there is a description in the RL11 documentation. (Me trusting my memory once more...)
> 
> That's different, though.  It describes the bad block table, which includes a pack serial number in its header.  Some device types use 144, some do not (in particular, on RP/RM there is a mix -- RP04/5/6 do not, RP07 and RM02/3/5/80 do).  The 144 table is purely a software construct, a bit of data placed by convention in the last few sectors of the drive and interpreted by the OS.  For example, in RSTS the bad block table is read to mark those blocks as unavailable, and the serial number is read and displayed during formatting but not otherwise used for anything.

Right. But that sounded what the OP was looking for. He noted that 
serial number and information was written to the pack. The serial number 
is never, as far as I can remember, for any disk drive, written anywhere 
in any header fields or similar. It's always just on a normal block. 
Most packs that have anything reserve the last track or similar for this 
kind of information. And that is what DEC STD 144 is about. For disk 
packs that do not follow that standard (if we only talk about DEC disks 
here), then there is no common area where a serial number will be stored.

   Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
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