[Info-vax] Kednos PL/I

[gah4]

On Thursday, September 14, 2023 at 7:38:58 AM UTC-7, Johnny Billquist wrote:

(snip)

> It's UMULH, but I agree. The Alpha was definitely designed for getting a 
> 128 bit result from 64 bit multiply. But it is done via two 
> instructions. MULQ;UMULH. If you want a signed MUL, you then need a 
> couple of more steps to adjust the result. But it's a simple thing. 
 
Okay, I found my "Alpha Architecture Handbook", copyright 1992.

I think I got it before machines were available for sale.

And what I had forgotten, and might have known 31 years ago:
There is no hardware integer divide.  

For divide by constant, you can usually, or maybe always, use the
high half of the double length product. 

And for variable divide, they suggest, but don't write out, a successive
approximation algorithm.  Presumably usually as a subroutine call.

There is floating point divide, though.