cvs commit: src/sys/boot/i386/boot2 boot1.s

Bruce Evans bde at
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> 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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