cvs commit: src/release Makefile
babkin at verizon.net
Wed Feb 1 09:14:51 PST 2006
>From: =?ISO646-US?Q?Dag-Erling_Sm=3Frgrav?= <des at des.no>
>Sergey Babkin <babkin at verizon.net> writes:
>> 1. It's slow, since BIOSes tend to use USB 1.x speeds, and even that
>> not in a really fast way. So the big images are best to be
>> avoided. Though probably it's still faster than floppies.
>It is significantly faster than a floppy, and comparable to a CD when
>you take into account the time required to spin up the drive and the
>slow seek times. It is also a lot less hassle than either (at least
>with modern PCs which have USB connectors in front)
Well, my experience was with GRUB and with UnixWare
loader, and for those the USB drive boot was much
slower than an IDE CD boot. The trick is that only
one spin-up and seek happen on the CD, after that
everything is read strictly sequentially at full
CD drive speed.
A 30MB image gets loaded from CD in no time, but
loading it from an USB flash drive took almost forever,
easily half an hour or so. Maybe the BIOSes became
more clever since then.
Of course, if you read not strictly sequentially,
a lot of seeks happen on the CD and the speed plummets.
The Really Bad case is when for each 2KB block
you read more data than neccessary (say, 4KB),
then discard everything beyond the first 2KB,
and then do the next read. This causes a seek on
every read. You wold normally think that the data
would be cached in the drive anyway, but apparently
the CD drive caches work in a strict FIFO order.
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