Re: Redbook on the new z196 mainframes.
- From: Terje Mathisen <"terje.mathisen at tmsw.no">
- Date: Tue, 03 Aug 2010 23:16:45 +0200
Bernd Paysan wrote:
Andy Glew wrote:256 *BYTE*?
2048 bits?
Line sizes 4X the typical 64B line size of x86?
These aren't cache lines. They are disk blocks.
What do you expect? Bandwidth and latency change differently. My rule of
thumb is that transfer time = access time, and that should work for disks as
That's identical to my own rule of thumb as well, I've been using it for many, many years. Among other things it means that the minimum transfer block size has increased by an additional order of magnitude or so during the time. :-)
well as for memories. The fact that disk sectors are still 512 bytes is
just legacy stuff, they should have increased to about a megabyte by now.
Disk sectors are for adressability, and backwards compatibility. The latter is important enough that some modern disks which work with larger sectors still have to emulate the old sector size, with dire consequences for disk partitions which aren't properly aligned. :-(
Terje
--
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"
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