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Re: New Vax - future directions :-)
Den 2021-07-06 kl. 11:48, skrev Johnny Billquist:
Well, nothing stops from allowing numbers strings in the future. They
are handled like the string instructions, so they can be interrupted.
The same with the other string instructions, no reason to have a limit
on the string length.
On 2021-07-06 11:28, Anders Magnusson wrote:
A side note: There is a very interesting part of the instruction set
that I think should be investigated more - the packed decimal
Those will in fact implement arbitrary precision in hardware, which
could be really nice to have when doing things like crypto
If you have two 64-bit values which you multiply, there is a fair
chance the result will not fit into 64 bits, and a carry won't be
enough to handle the overflow. :-) Then what? Just give up. Leave
it all to be done in software? Or add some instruction that can
Yes, do it in software. You don't have any modern language that
want to deal with the upper part anyway.
Ok. Fair enough. That wasn't a very meaningful example or question.
(Well, it's meaningful sometimes to assembler programmers, but
hardly for any higher level language.)
But for the VAX32, having support allowing for efficient
multiplication of 64-bit values is something I see value in.
I sortof see the same for a VAX64 to efficiently deal with 128 bit
multiplications as well.
But as this does not extend to larger values, maybe it's
questionable how much value it do have in the end.
That's an interesting view. I've always looked at the packed decimal
stuff as mostly targeted at Cobol and financial applications.
You need to remember, though, that packed decimal strings have at most
31 digits. So not entirely arbitrary. (Hmm, not entirely sure if it is
31 digits, or 31 bytes...)
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