On Tue, 10 Feb 1998, der Mouse wrote:

> > IIRC the MicroVAX I is probably the least of the VAXen - [...], and
> > (most important) without a full implementation of the instruction
> > set.  (It has to emulate some of the lesser used instructions).
> 
> That is also true of the MicroVAX-II, that it has to emulate some of
> the less-used instructions in software.  In the case of the uVAX-II,
> executing one of the "macrocoded" instructions amounts to taking a trap
> to the kernel....
> 
> 					der Mouse
While were off topic...

True - In fact one of my students discovered in an assembler class I was
teaching that some of the packed decimal instructions were crashing
his program he had written in assembler under Ultrix.  I assumed that
usually when a student's assembler program crashes it is due to some
problem with the student's code.  I examined the code very carefully and
found several mistakes but not related to where his program was crashing.

I came up with a simple example of how it failed and contacted digital.
I assumed that if some of the packed decimal instructions were `micro
coded' wrong that COBOL users would be hosed.  While we had one of the
earlier MVIIs I could not understand why this had not been detected
before.  When I talked to the support person after he came up with a patch
for the OS relative to the `micro code' I asked him why this had not 
impacted VMS users of COBOL.  He explained that the Ultrix and VMS people
developed their own `micro code' independently (I was shocked - but I
guess I should not have been) and VMS people had gotten that one right
while the Ultrix people had not.

johnh...