MVS had simulation for DAS in its program check handler, which
allowed SP1.2 and its successors to run on machines which did not
have DAS.  DAS was first implemented via a microcode update
on the 3033.  It was never implemented on 158 and 168.
 
Jim Mulder z/OS Diagnosis, Design, Development, Test  IBM Corp. 
Poughkeepsie NY


"IBM Mainframe Discussion List" <[email protected]> wrote on 
09/04/2020 06:47:52 AM:

> From: "Greg Price" <[email protected]>
> To: [email protected]
> Date: 09/04/2020 11:45 AM
> Subject: Re: Architectural Level Sets
> Sent by: "IBM Mainframe Discussion List" <[email protected]>

> I was very surprised when MVS/SP 1.2 ran on the 158 because I would have 

> thought that DAS required extra hardware that was not thought of when 
> the 158 was first designed and built.

> 
> And also...
> 
> Is not one of the main points of an ALS is that the the BCP (et al) 
> coders can assume that the newer instructions in place at that level can 

> be freely used within the object code of their components?



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