ken@turtleva.UUCP (07/05/83)
One of the best features in some of the newer microprocessors (29116,
RISC) is a barrel shifter. The 29116 allows only rotates, but the RISC
also allows arithmetic and logical shifts in one cycle. The barrel
shifter makes it much easier to work with packed data (especially with
the 29116's rotate, mask, and merge instruction), and also helps when
converting between data types that have the radix point in different
positions. Are there any other processors, present or future, that
have this component? I suspect that it is almost a necessity in 32-bit
micros.
Ken Turkowski
{decwrl,amd70}!turtlevax!kenparnass@ihuxf.UUCP (07/06/83)
"One of the best features in some of the
newer microprocessors (29116, RISC) is a
barrel shifter....... Are there any
other processors, present or future,
that have this component? I suspect
that it is almost a necessity in 32-bit
micros."
As shown on page 35 of the July 1983 issue of IEEE Spectrum
magazine, the Bellmac1 -32, designed by Bell Laboratories,
contains a "barrel switch".
Robert S. Parnass
Bell Laboratories
Naperville, Illinois
ihnp4!ihuxf!parnass
__________
1. Bellmac is a trademark of the Western Electric Company.ucbesvax.turner@ucbcad.UUCP (07/11/83)
#R:turtleva:-20900:ucbesvax:12800004:000:808 ucbesvax!turner Jul 9 16:56:00 1983 Indeed, I was quite indignant when I discovered that 68000 shift/rotate timing was (sigh) a distinctly linear function of the number of shifts. I suppose barrel shifters do rather horrify the micron-hackers, since it's just a big array of simple switches. How can anything that clean-looking be useful? (Oh know, I don't really believe that they think things like that. How do you say in netspeak? ":-)") But yeah, 32 bits is a lotta bits. 32-bit machines almost *need* to be virtual, I think, since there's so many high order bits sitting around in memory being 0 or 1 most of their lives. Better bit-field support in high-level languages and the use of folding algorithms in loop optimization would both probably help a lot. From the Mental Blocks of Michael Turner, ucbvax!ucbesvax.turner
phil@amd70.UUCP (07/15/83)
I understand the press has already gotten hold of this, so it should be ok to say that AMD is doing a 29530 16 bit expandable barrel shifter, maybe available in 1984. I don't have any more information.