cvs commit: src/sys/boot/i386/boot2 boot1.s
bde at zeta.org.au
Sat Aug 30 03:04:12 PDT 2003
On Sat, 30 Aug 2003, Dag-Erling [iso-8859-1] Sm=F8rgrav wrote:
> Warner Losh <imp at FreeBSD.org> writes:
> > Log:
> > Many newer CF do not handle having the entire track read from them at
> > boot time. Instead, read it a sector at a time. While this sounds
> > like a significant slowdown, I've not been able to measure any
> > signficant difference.
> It should make a big difference on floppies.
Probably not even there for suitably modern hardware. Try
"dd if=3D/dev/fd0 of=3D/dev/null". It reads mostly as fast as possible, 1
sector at a time, although there is no track buffer in the driver. It
only misses reading the next sector and has to wait for 1 revolution
after seeking, and naively implemented track reads would have the
same inefficiency. I think all hardware newer than 8-10 years old
can keep up doing single-sector reads, at least with the FreeBSD
driver, but my BIOSes couldn't keep up in 1993 when I implemented
the track buffer in biosboot.
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