From owner-freebsd-hackers Thu May 21 05:49:06 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id FAA01372 for freebsd-hackers-outgoing; Thu, 21 May 1998 05:49:06 -0700 (PDT) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from animaniacs.itribe.net (gatekeeper.itribe.net [209.49.144.254]) by hub.freebsd.org (8.8.8/8.8.8) with SMTP id FAA01366 for ; Thu, 21 May 1998 05:49:02 -0700 (PDT) (envelope-from jamie@itribe.net) Received: from localhost (jamie@localhost) by animaniacs.itribe.net (950413.SGI.8.6.12/950213.SGI.AUTOCF) via SMTP id IAA03004; Thu, 21 May 1998 08:36:38 -0400 Date: Thu, 21 May 1998 08:36:38 -0400 (EDT) From: Jamie Bowden To: Peter Jeremy cc: hackers@FreeBSD.ORG Subject: Re: Intel vs the rest (was `Original PC' and `talk') In-Reply-To: <199805202156.HAA15942@gsms01.alcatel.com.au> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Thu, 21 May 1998, Peter Jeremy wrote: > As an example of the impact of an architectural decision on > complexity: The 68k included a clear split between (non-modifiable) > instructions and (modifiable) data, the x86 didn't (and early > applications often used self-modifying code). This means that the x86 > needs a unified cache, whilst the 68k uses a split cache - which gives > it two immediate advantages: The I-cache is also somewhat simpler (no > need for dirty bits or the write-{through,back} logic), allowing more > of it for the same complexity. Dual caches allow parallel I and D > accesses - ie effectively doubling the cache <-> CPU bandwidth (dual- > porting the cache can be done, but entails a substantial increase in > complexity). (The downside is that a unified cache will adjust to > different code vs data footprints - giving somewhat better hit rates > for a given total cache size). I have both. Data cache size: 16 Kbytes Instruction cache size: 16 Kbytes Secondary unified instruction/data cache size: 512 Kbytes on Processor 0 All hail high end workstation makers. This is the SGI on my desk, lowly Indy that it is. Jamie Bowden System Administrator, iTRiBE.net To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message