OT: How to debug ZIP drive

Richard Lightman richard at reika.demon.co.uk
Sat Oct 20 01:02:54 PDT 2001


Misquoted from Skip Gaede on 2001/10/16 at 20:24 +0000:
> 
> I'd like to restate what I know about the ZIP drive, now that I've done 
> some more homework.
> 
> There are two drivers which can be used to talk to the drive, SCSI 
> (emulation) and ide-floppy. Of the two, the ide-floppy seems more 
> sophisticated, as I can configure the drive as either a large 95 cylinder 
> floppy, or as a small 96 cylinder drive with a partition table (in BIOS 
> setup). The ide-floppy driver notices the difference -- the SCSI emulation 
> still sees the drive as 95/64/32 no matter what.
> 
The zip drive understands SCSI commands. These are sent over the IDE
bus using the ATAPI protocol. Limitations in the IDE standard, and
BIOS require a system of translation to C/H/S format that has nothing
to do with the real geometry. Many years ago, people optimized data
to match the physical geometry of the disk. SCSI reports a geometry
for compatibilty, but this has had nothing to do with the real world
for over 10 years.

I use the SCSI drivers for an IDE zip drive because it removes
one layer of confusion.

> The mke2fs program does succeed, eventually, in formatting the partition, 
> but it missed about 112 interrupts during the format operation, causing the 
> driver to do a RESET operation for each one. The ide-floppy driver uses 
> packet writing technology, and has been revised several times this year. I 
> think it isn't quite ready for prime time yet under the 2.4 kernel. For one 
> thing, it took almost two hours to format an 85 MB partition, compated to 2 
> minutes under Win2000 to do the whole 95 MB.
> 

Try "cat /proc/interrupts". I suspect your SCSI controller is shareing
an interrupt with one of the IDE controllers. Sometimes drivers do
not work well when shareing an interrrupt. It may be possible to tell
the driver for the SCSI card to use a different interrupt. Moving the
SCSI card to a different slot may help (The first 4 slots are wired
differently, but any others will probably be the same as the 4th).
You may be able to change the interrupt used by the IDE controller
from the BIOS.


> So, it works, sort of, and it's slower than molasses. There are a bunch of 
> tweakable parameters in /proc/ide/hdc/settings. I have not found much in 
> the way of documentation on them, however.
> 
Try hdparm:
http://www.ibiblio.org/pub/Linux/system/hardware/

Richard

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