Date: Thu, 21 May 1998 08:36:38 -0400 (EDT) From: Jamie Bowden <jamie@itribe.net> To: Peter Jeremy <peter.jeremy@alcatel.com.au> Cc: hackers@FreeBSD.ORG Subject: Re: Intel vs the rest (was `Original PC' and `talk') Message-ID: <Pine.SGI.3.96.980521083324.1012M-100000@animaniacs.itribe.net> In-Reply-To: <199805202156.HAA15942@gsms01.alcatel.com.au>
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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
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