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Re: New Vax - future directions :-)


> is what I am uncertain about. And your answer just confused me. :-)

It clears R0 and R1.  On VAX-32, that is.  It remains to be determined
what it would do on VAX-64 (in 64-bit mode, if the hardware is to be
dual-mode).  Personally, I would say it should clear just R0 (but all
64 bits of it).

Whether VAX-64 CLRQ uses the same opcode as VAX-32 CLRQ would be
another open question.  I could argue it either way.

> But then we have much more freedom as well, and can indeed change
> addressing modes, instructions and registers any way we want to.

Of course.  But, so far, insofar as I'm seeing a consensus, the only
thing that there is consensus on changing is the VM system.  The VAX-32
VM system is...a bad fit to the task.  (If it were being designed
today, I'd say it's even a bad fit to the 32-bit task.)

Arguably switching to IEEE FP is another, but that feels a bit less
consensusy to me.

I really wish there were an open FPGA design; I'd like to experiment
with some of this myself.  But the closest I've been able to find is
reverse-engineered, not actually documented.  (But admittedly it's been
a year or two since I looked.)

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