Date: Fri, 21 Feb 1997 00:05:49 -0800 (PST) From: "Bryan K. Ogawa" <bkogawa@primenet.com> To: bde@zeta.org.au Cc: hardware@freebsd.org, bde@zeta.org.au, dkelly@hiwaay.net Subject: Re: _big_ IDE disks? Message-ID: <199702210805.AAA22530@foo.primenet.com> References: <> <199702210543.QAA29486@godzilla.zeta.org.au>
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In localhost.freebsd.hardware you write:
>>> Run `dd if=/dev/zero of=/dev/null bs=1m count=1000' and complain if
>>> the throughtput is much lower than 120MB/sec.
[...]
>My comment only applies to P5's with a 66MHz memory bus. The speed should
>be much the same for CPU speeds of 100MHz and larger multiples of 33[.3]MHz.
>The above dd command essentially copies the same 4K kernel buffer to
>sequential memory 256 times. . The kernel buffer stays in the L1 cache
>so reading it is almost free and the speed approaches the maximum main
>memory write speed which is 133M * 4/3 on my P5/133 (I think it is for
>a 6-2-2-2 burst cycle).
Hm. I can only get about 100MB/seg doing this, max (P5/133). I did
it with an X server running--should that matter?
{foo} ~ 0:01 ttyp3 > uname -a
FreeBSD foo.primenet.com 2.2-ALPHA FreeBSD 2.2-ALPHA #5: Sun Jan 12 19:28:01 PST
1997 bkogawa@foo.primenet.com:/usr/src/sys/compile/ATWO i386
{foo} ~ 0:04 ttyp3 > dd if=/dev/zero of=/dev/null bs=1m count=1000
1000+0 records in
1000+0 records out
1048576000 bytes transferred in 10 secs (104857600 bytes/sec)
Perhaps my BIOS is mis-set, but I wouldn't think so...?
--
bryan k ogawa <bkogawa@primenet.com> http://www.primenet.com/~bkogawa/
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