Date: Thu, 21 May 1998 10:56:36 -0400 (EDT) From: Chuck Robey <chuckr@glue.umd.edu> To: Jonathan Lemon <jlemon@americantv.com> Cc: Soren Kristensen <soekris@alameda.net>, hackers@FreeBSD.ORG Subject: Re: Original PC and talk Message-ID: <Pine.BSF.3.96.980521105326.312j-100000@localhost> In-Reply-To: <19980521072302.21950@right.PCS>
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On Thu, 21 May 1998, Jonathan Lemon wrote: > On May 05, 1998 at 11:47:17PM -0400, Chuck Robey wrote: > > All those tricks (the same ones) are why processors like the DEC Alpha > > are so hot. Things like register renaming don't give you much > > improvement if you're talking about such a tiny humber of registers to > > begin with (referring to the X86 here). > > Huh? > > Register renaming (from the architecture's point of view) only refers > to the internal on-chip registers (reservation stations), not the > externally visible registers (from the compiler's point of view). It uses those invisible internal registers to store things coming from or going to real registers. The strategy is far more useful when there are more registers _to_ rename. > > There can be a lot of internal registers. These are marshalled and > committed (or squashed) by the reorder buffer at the end of execution > (assuming a relatively modern chip here). > > This reordering does give a performance boost, even if there are only > a few architecturally visible registers, as in the case of x86. > -- > Jonathan > > ----------------------------+----------------------------------------------- Chuck Robey | Interests include any kind of voice or data chuckr@glue.umd.edu | communications topic, C programming, and Unix. 213 Lakeside Drive Apt T-1 | Greenbelt, MD 20770 | I run Journey2 and picnic (FreeBSD-current) (301) 220-2114 | and jaunt (NetBSD). ----------------------------+----------------------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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