🚀 go-pugleaf

>>>>> On 23 Oct 92 14:44:40 GMT, ishikawa@ds5200.personal-media.co.jp (Chiaki
>>>>> Ishikawa) said:

Chiaki> Hello.

Chiaki> I attended an Alpha exhibition hosted by Japan DEC near Tokyo
Chiaki> Disneyland.  I had a chance to talk to someone who worked on Alpha
Chiaki> compiler such as C and Fortran (and presumably BLISS, too).  He said
Chiaki> ALPHA doesn't have a byte manipulation instruction. Eh, rather, he
Chiaki> said its memory access is done in only 32 bit or 64 bit. So character
Chiaki> manipulation has to be done by word access, and then masking and
Chiaki> operation.

Chiaki> I know it is possible, but wouldn't it be a little clumsy to
Chiaki> manipulate character data on Alpha?

This is a decision that the hardware designers made after very careful
consideration of all the performance ramifications. They seem to come to the
conclusion that, given typical usage of 64-bit, 32-bit, and character
operations, offering 64- and 32-bit loads/stores was a good idea and that
(though convenient) having byte loads/stores would slow down overall program
execution by complicating the processor in some places. It is exactly this
sort of delicate design decision they get paid for, and presumably good
decisions are part of why the Alpha clock can be so fast. In the Alpha
handbook they detail how to extract bytes, etc., and there are nice
instructions to help one do so.

Note: this question really should have gone to comp.arch, but what the heck ....
--

J. Eliot B. Moss, Associate Professor	Visiting Associate Professor
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