PDP-11 disk image question

Paul Koning paulkoning at comcast.net
Wed Feb 20 07:52:56 CST 2019

> On Feb 19, 2019, at 11:55 PM, Glen Slick via cctalk <cctalk at classiccmp.org> wrote:
> On Sat, Feb 16, 2019 at 1:20 PM Bill Gunshannon via cctalk
> <cctalk at classiccmp.org> wrote:
>> I have a CQD=220A/MT configured for 6 disks and one tape.
>> As for disk types, you can toggle RA ON or OFF on each drive.
>> You can specify one RA type that will be in effect for any
>> disk with RA ON.  Types are: RA70, RA80, RA81, RA82, RA90 and RA92.
> Looking at this further, I don't believe the CMD CQD RA type option
> does what you think it does. I don't believe it has any effect on the
> reported geometry of the MSCP unit, I believe it only changes the
> reported type name of the MSCP unit.

So this might be relevant.  If the reported size is sufficiently different, things will break.  

For MSCP, RSTS cares about the device size (LBA count).  It pays no attention to reported "geometry".  It displays the reported device type string (in INIT "Hardware List" option) but it doesn't care about what those are.  If a gigabyte disk claims it's an RX50 (or an RX98), RSTS will happily display that string without any objections.


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