Port-vax archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

Re: New Vax - future directions :-)

On 2021-07-06 15:11, Paul Koning wrote:

On Jul 6, 2021, at 5:08 AM, Johnny Billquist <bqt%Update.UU.SE@localhost> wrote:

Well, the processor handbook even have the description on how you use EMUL and MUL to do multiplication of two 64-bit values. Without EMUL it becomes a much larger and more tedious process to multiply 64-bit values. But yes, it's only usable for signed multiplications. Which is annoying. (And is the same problem on the PDP-11.)

Turning a signed multiply into an unsigned one isn't very hard.  Unsigned div is another matter, unfortunately.

Hmm. I tried to figure that one out before, without much success. I've done various silly things like halfing a value if it's too big, and then double the end result, and other silly things. But they all feel rather unelegant.
You have a better way?

And yeah, divide have always been even worse. :-)


Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt%softjar.se@localhost             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

Home | Main Index | Thread Index | Old Index