[Info-vax] Hobbyist licences for VAX

[Bob Eager]

On Fri, 15 Apr 2022 12:51:24 +0100, David Wade wrote:

> On 14/04/2022 23:00, gah4 wrote:
>> On Thursday, April 14, 2022 at 6:38:13 AM UTC-7, Bob Eager wrote:
>>> On Thu, 14 Apr 2022 01:07:56 -0700, gah4 wrote:
>> 
>> (snip)
>>>> And, in case you were wondering, there is a difference in the IBM and
>>>> Hercules form when using the track overflow feature, which as far as
>>>> I know only applies to the 2314 and 3330. That allows a block to
>>>> start on one track and continue onto the next track.
>> 
>>> Hmm. Might have to do my own. The track overflow feature is something
>>> I *have* to implement.
>> 
>> They do implement it, but IBM and Hercules implement it in a different
>> way.
>> I think it is only one bit somewhere that is in a different place.
> 
> I don't believe there is any difference EXCEPT Hercules supports
> compressed images and also shadow files. Certainly files from my P390
> work under Hercules.
> 
> 
>> Early in the Hercules years, there was interest in running the freely
>> available (before software copyright existed) MVS 3.8j.  It seems that
>> IBM uses track overflow for the paging file, so it has to work!
>> 
>> 
> It looks like there some connects in the Hercules source about track
> overflow so it certainly supports it now

Thanks. This is all useful stuff. The disks I will be emulating are 
obviously from the same OEM; slightly different programming (and 
completely different at the controller level) but the same format will be 
good.

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