IBM channel-attached DASD emulation

[Christian Gauger-Cosgrove]

On 25 December 2015 at 20:55, Mike Ross <tmfdmike at gmail.com> wrote:
> What do people reckon would be the best target for emulation? 3340
> springs to mind initially... would that work on machines as old as
> System/360s? It's about the *only* option for 5415 DASD...
>
The 3340 is a pretty "small" disk at least for mainframe DASD.

More useful would be the 3330-1 and 3330-11. You can gen OS/360 21.8F
and MVS 3.8J to 3330 (assuming of course you have a 370 of some sort
knocking around).


Unless I'm completely wrong, most of the various control units
presented a programming interface that was relatively similar/the same
amongst the various kinds of DASD (looking at the 2844/2314 and
3830/3330 for example). Naturally the best way to double check that
would be to look at sufficient reference manuals, though if you felt
less inclined you could try browsing the source of the Hercules
emulator for how it does DASD emulation.


Now for the topic of System/3 DASD; firstly the control "speaks" a
completely different set of commands compared to the channel attached
DASD of the "proper" mainframe world. The 5444 disk is it's own thing
and not related to any of the channel attached DASD. The 5445 is
basically a single 2314 unit; and the 3340/3344 are exactly what they
say they are. Images of the 5445 and 334x drives would be
interchangable with the 2314 and 334x (since the format the System/3
uses on those disks is compatible with mainframe systems).


As a kind of dumb thought, for storing the images of the
Count-Key-Data DASD perhaps abuse the Hercules CKD/CCKD code into the
hardware emulator? (Means you can move your emulated disk packs to and
from a Hercules instance if you had reason to do so.)


Sorry for blathering on, I'm not an expert and I haven't a clue how
easy or difficult it would be to implement any of these ideas.


Cheers,
Christian
-- 
Christian M. Gauger-Cosgrove
STCKON08DS0
Contact information available upon request.