Re: [PARPORT] Aha !

David Campbell (
Sat, 12 Sep 1998 08:18:17 +0800

> Finally, is this indicative of a flakey drive or PP? Should I try to
> return the Sparq for a replacement or seek a differnt momboard? (The PP
> is built into the motherboard.)

Do you have access to a second machine to test the drive. There
are a number of IO chipsets which are known to cause problems:

a) Early WinBond chipsets have bad EPP timing
b) Some "beta" NatSemi IO chipsets have broken EPP.

The "beta" NatSemi chipsets were released for testing/development purposes
but found there way into some mainboards. Very few and far between.
WinBond have fixed their problems about a year ago (can not confirm this).
> Are other brands (IOmega?) of PP drives with removable media less prone to
> this kind of bug? I don't remember this kind of problem when I was using
> a 486 board (AMDx86-133) with the PP built-in.

Iomega with their drivers keep an eye out for "buggy" chipsets and use PS2
mode when they are found (from verbal conversation with Iomega driver

> Perhaps the speed of this CPU (AMDk86-200 w/MMX) is trying to push
> the PP too fast?

This is a mainboard issue since the board has something like three different
bus speeds (CPU, PCI and ISA). The PCI <=> ISA bridge on some mainboards
is known to flakey when doing 32 bit IO. What happens is that the correct
amount of data is transfered but some of the bytes are replicated and overwrite
other bytes. eg:

Drive ParPort ISA Bus PCI Bus

Trouble is that not many devices on the ISA bus expect 32 bit IO, the only
device that would regularly use 32 bit IO would be IDE (which now hangs
off the PCI bus).

Without reading Grant's mind I do not know if the PARIDE driver complains
if the device returns different amount of data than expected.
eg: 511 or 513 bytes when 512 expected.

SCSI complains bitterly since the last byte is the status byte. The mid-level
driver will only allow something like 10 possible answers. Any other and the
kernel panics (I know from experience :-).

> What were you saying about discovering that EPP-32 was prone to problems
> with some makes and brands of PP drives? I'm feeling less eager to
> purchase PP drives in the future and may try to stick with scsi, ide,
> and/or USB drives (when they're available and linux supports them).

My tests shows that most hardware throttle the ISA bus to 1.0E+6 accesses
per seconds (asm loop polling a single port). This puts an upper limit of
arround 1MB/sec through a parallel port. This would be considered a
"poor" drive by IDE or SCSI standards.

The one thing about parallel ports is that nearly every machine has one.
(Although not every parallel port is equal)

> I hope my difficulties with this will help others who may not even be
> aware yet that they HAVE a problem with the integrity of their data (in
> linux) on their Sparq drive. Maybe someone could post this in one of the
> newsgroups, although I don't see much there along technical lines of
> discussion regarding PP drives....mostly just gripe fests.

I will join the gripe fest when *every* PC comes with an external SCSI
connector (or maybe even USB). Until then every PC will still have a
parallel port.

David Campbell

"There is no such thing as a bug in the Linux 2.1.x kernels
Consider it as a request from the enlightened for you to brush
up on your C programming and help improve the kernel."

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This archive was generated by hypermail 2.0b3 on Wed 30 Dec 1998 - 10:18:16 EST