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From: jgh@root.co.uk (Jeremy G Harris)
Newsgroups: comp.arch
Subject: Re: Cache Line Fills -- Critical Word First
Keywords: cache memory
Message-ID: <2454@root44.co.uk>
Date: 3 Oct 90 09:00:50 GMT
References: <34275@cup.portal.com> <14780@cbmvax.commodore.com> <41856@mips.mips.COM>
Reply-To: jgh@root.co.uk (Jeremy G Harris)
Organization: UniSoft Ltd, London, England
Lines: 24

In article <41856@mips.mips.COM> mash@mips.COM (John Mashey) writes
yet another long and informative exposition....
>[...]
>For the I-cache, when you have a cache miss:
>	I1) You can stall the machine, fetch the entire cache block,
>	then restart.  This is clearly the simplest.
>	I2) You can do "early restart", where you begin executing as soon
>	as the requested word is available.  [...]
>	I3) You can do "out-of-order fetch" in addition to early restart,
>	and then do "wrapped fetch", so that you wrap-around to complete.

Does anyone do:

I4) Out-of-order fetch with early restart but without wrapped fetch?
Extra hardware is needed to mark unavailible words within the line;
would checking these marks be too slow?

(orthogonal possibility)
XX) Prefetch of next line on access of last word of line?


Disclaimer: I've never designed a memory system.
-- 
Jeremy Harris			jgh@root.co.uk			+44 71 315 6600