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Re: New Vax - future directions :-)

> On Jul 5, 2021, at 1:12 PM, Johnny Billquist <bqt%update.uu.se@localhost> wrote:
> On 2021-07-03 15:46, Anders Magnusson wrote:
>> So, some thought about expanding the Vax architecture.
> Interesting topic, yes...
>> 64-bit:
>> For userspace; the vax architecture itself leave the door open for expanding the word size.   The instructions are all defined to use only the part of a register it needs, so adding a bunch of 'Q' instructions are a no-brainer.  Argument reference will work as before.
> Indeed. There are even some instructions that already exists in Q format. However, I am unclear what actually happens if you do a
> does it clear R0 and R1, or just R0?

The SRM is clear (so to speak) about that: 64 bit operations on registers touch the register pair.  So CLRQ R0 clears R0 and R1.  Similarly, CLRO R0 (if your machine implements that) clears R0 through R3.


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