[Info-vax] date comparison format from a program

[Dave Froble]

On 5/21/2019 12:29 PM, Hans Bachner wrote:
> Dave Froble schrieb am 21.05.2019 um 16:43:
>> [...]
>>
>> Now, I may be wrong, same old territory for me, but, if I was designing
>> something that had to last for a long time, I'd design it with "black
>> boxes" that perform a task, but can be replaced (inside the box) with
>> newer stuff.  As long as the "box" did what it was suppose to do, so
>> what?  More viable, probably cheaper.
>>
>> [...]
>
> Well, this is exactly what an emulator like CHARON-VAX does.
>
> (Open)VMS accesses a "black box" which can be a physical VAX or an
> emulated VAX. As long as both (re)act identically to any given input
> (e.g. a driver sending some signal to a storage controller), everything
> is fine.

Usually.  There can be issues such as timing.  But I do agree with you 
on this.

> As I mentioned Stromasys licensed hardware diagnostic routines from DEC
> to verify that you can't tell what's in the "black box". As long as a
> "black box" is certified for a given application (and not the components
> inside the box), replacement of physical hardware with an emulator is
> not an issue. There are quite some cases where the emulator was accepted
> by the certification authorities.

But also some who would not it appears.


-- 
David Froble                       Tel: 724-529-0450
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