Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!pyramid!voder!apple!landon
From: landon@apple.UUCP (Landon Dyer)
Newsgroups: comp.sys.atari.st
Subject: Re: TOS bug ?
Message-ID: <7095@apple.UUCP>
Date: 23 Dec 87 17:00:50 GMT
References: <8712211936.AA01429@ucbvax.Berkeley.EDU>
Organization: Apple Computer, Inc., Cupertino, USA
Lines: 35

> I have run into some problems as i tried to copy files to a Harddisk.
> I had 2 SH205-Harddisks connected to my Mega ST4 and tried to copy a (german)
> TeX-Distribution from one Harddisk to the other. The fonts are located in a
> couple of subdirectories all named 'PXLnnnn', where 'nnnn' stands for a four
> digit number. I tried to copy the directories by opening two windows,
> selecting 4 directories and pulling them in the other window. For the first
> 2 or 3 directories all works well, but then suddenly the name of one of the
> directories will change! The 'X' of 'PXLnnnn' will turn in the Sqare-Root-
> Symbol or in a superscript '3'.

Single-bit errors on DMA transfer.

If you have SH205 cables longer than eighteen inches they will not work
reliably.  If you have home-brew unshielded cables, or you have defeated
the shielding (with a Y-cable), the same applies.  [If your cables are
longer than 18" and they came in the box with the SH205, let atari!neil
know about it!  And get them replaced.]

SCSI data transfers (at least on the ST) are not checksummed or
otherwise validated.  The DMA bus doesn't have much fail-safe, and you
can run for a long time before noticing sporadic single-bit errors.

A simple test you can try is to read the same set of blocks over and
over again (with Rwabs()) and compare consecutive reads; let it run
overnight and see if you get any errors.

It's sad that the ST's only high-speed port is fraught with so much
flakiness and folklore about its use.  If there's a single piece of
hardware Atari should improve on the ST, it's the reliability of the
DMA bus.  [Sorry, John.]


-Landon
-- 

I speak for me.