Re: SCSI and EIDE

[Rob Browning <osiris@cs.utexas.edu>]

Sherwood Botsford <sherwood@space.ualberta.ca> writes:

> I agree that you can do this in the OS, but I don't think that it
> *should* be done in the OS.
> 0.	In general smarts should be at the point they are used. We had a
> VAX that was about as speedy as a 12 MHz 286 with 287 co-processor.
> However, that vax could handle 8 simultaneous 19 KB terminal lines.
> How?  Smart serial cards.  
> 	The CPU should do those tasks that are either too general for
> dedicated hardware, or that don't happen often enough to take up much
> time.
> 1.	The OS shouldn't have to care about the layout of the disk.

Not trying to start a flame war here, but if the overhead to the cpu
is minimal, which I would guess it is for seek algorithms, you are
often better off doing it with the cpu.  Mainly because changing the
algorithms, fixing bugs, trying out new approaches, etc. can happen
with a simple kernel recompile, and improvment's in CPU speed (which
happen all the time, as opposed to the somewhat slower embedded
controller market) immediately translate to improvements in algorithm
speed.  Now if the disks just had some flash ROM and a 386 (or
equivalent that gcc knows about) on board, things might be different.
Either that or a couple of cheap 386's on the motherboard for stuff
like this...

I'm mostly just speculating.  I don't know that much about drive
hardware.

--
Rob