Date   : Thu, 23 Jul 1987 05:37:14 GMT
From   : poisson.usc.edu!mlinar@OBERON.USC.EDU (Mitch Mlinar)
Subject: Re: (none)

In article <8707221530.AA05113@primerd.prime.com> ELLIOT@S34.UUCP writes:
>
>I have a package from Software Publishers Inc. of Arlignton Texas which
>converts the 8" floppies of my Xerox 820 from single density to one of seven
>formats of double density.  The version I have is dated 15 March 1982.  The
>problem is that occasionally and inconsistantly, sectors are wiped out
during a
>write.  Of course, I don't know this until I try to read them (BIOS error...).
>I believe that the hardware headers are wiped out and that the controller
>cannot read the sector (DU can't read the bad sectors).  This happens
even when

Well, you hit jackpot!  I, and about 12 other people I know, all have SWP on
at least one system (2 for me).  And guess what - no problems to speak of.
There ARE drives that do not work well with it, among them are Mitsibushi and
Remex.  Shugarts and Panasonic work the best, although even Tandons do fine.

15 Mar 82 was the last version of ANYTHING by SWP: they are still in business
with a 68000 multi-user system and no longer sell or support the SWP cards.
The "guru" who invented the whole thing sold off and left, and Z-80 is some
archaic buzz-word from the past for the current crew....

>
>My question, then, is this:  Does anyone know if this can possibly be
tied to a
>bad release of the BIOS or the controller hardware where an update would fix
>the problem (and if so, does this company still exist; there are no sources
for
>the BIOS - I can't see that software could do this kind of damage)?  Or is
>this a media problem (I've been using Sony SSDD, though they may be old). Or
>are my drives out of alignment or dirty (I've cleaned the heads; the

SWP does not sell source, but MicroCode Consulting sells a BIOS for SWP with
their QP/M package: source for the BIOS is included (as well as the monitor).
A distributor is (still?) Emerald Microware (503) 641-0347.  The guy there
is also quite knowledgable about drives and also has hard disk upgrades which
plug into the Z80 slot and, through a Western Digital card, talk to up to
2 hard drives of 64M each.  (I have only 20M on mine, which is plenty; there
is no hard drive on the other ... sigh.)

My first guess would have been hardware, although the code COULD be damaged.
However, if that was really the case, then ANY density should fail rather
than getting better as less (density) stress is applied to the disk.  Don't
forget, this sucker is humping along at 2.5MHz and there is NO room for error.
It does not take much to miss the 1st sector with such a slow Z80 rate...

Another problem could be the floppies you are using; although 5.25 stuff is
very forgiving at double density (even if not marked), at least on this
package, poor 8" floppies show the same lousy symptoms discussed.  I use
strictly Maxell or IBM or Dysan (Xerox and BASF do not work well).  They must
be certified double-density - I swear that controller reads the bloody label
and refuses to work error-free when it sees a single-density disk while writing
at double-density!!!

Hope this helps.  Let me know how this comes out.  It is a really nice system
for vintage CP/M.

-Mitch