[Simh] RB09 == RD10

[Bob Supnik]

Thanks, Tim. Burroughs made a lot of fixed head disks at the time. I 
can't identify the model, but the IA2 (see page 7-4 of the B6700 
Hardware Handbook, on bitsavers) seems like a possibility. It has 7552 
sectors per surface vs 8000, but Burroughs sectors were longer than DEC 
sectors (180 x 8b = 1440b vs 32 x 36b = 1152b), so perhaps DEC format 
had more sectors per track.

While the 18b- and 36b-groups used the same disk buyout, they went to 
different vendors for drums. The Type 24 and RM09 came from Vermont 
Research; the RM10B from Bryant.

/Bob

On 2/27/2016 12:00 PM, simh-request at trailing-edge.com wrote:
> Message: 3
> Date: Sat, 27 Feb 2016 09:31:59 -0500
> From: Timothe Litt<litt at ieee.org>
> To:simh at trailing-edge.com
> Subject: Re: [Simh] RB09 == RD10
> Message-ID:<56D1B35F.3040206 at ieee.org>
> Content-Type: text/plain; charset="utf-8"
>
> On 27-Feb-16 08:23, Bob Supnik wrote:
>> >Max Burnet gave me a pointer from some old price lists, showing that
>> >the RD10 had very similar specs to the RB09. The RC10 manual confirms
>> >it - same BCD addressing of tracks and sectors, same number of tracks,
>> >same sectors per track, same words per sector (32 x 36b for the RD10,
>> >64 x 18b for the RB09). So the "RD10s" on some PDP-9s in the services
>> >listing are actually RB09s, at least at the drive level.
>> >
>> >I still don't know what an RC09 is. Alternate name for an RB09?
>> >Half-sized variant? Another mystery is who made the actual drive
>> >mechanism. It precedes DEC's first internally designed fixed head
>> >disk, the RF09/RS09, by two years.
> According to the option module list, the RC09 is a "Control for
> Burroughs Disk"  The design engineer was J. Milton.
>
> That makes sense, as the RC10 was the PDP10 controller for disk and drums.
>
> FWIW, Family members: the RD10 was made by Burroughs.  The RM10B drum
> was by Bryant.  SW documentation was removed from the PDP-10 doc set in
> the 80s, but as I wrote previously, I believe the tech manuals are on
> the FS microfiche.  The section with the red stripes on top.
>
> The drums were notoriously unreliable.  Especially the ones in the Mill,
> though things improved when someone realized that they tended to crash
> when semitrailers bumped into the loading dock above them....