ISC 3.2/harddisk & floppy problems

[Ralph-Diether Marzusch]

   This is a summary of a discussion regarding certain floppy and harddisk 
   problems under ISC UNIX (2.0.2 and 2.2.1). This topic has recently been 
   discussed in a local german newsgroup. Since nobody came up with a solution 
   to this problem I'm summarizing and repeating it here:


Due to additional hints and experiences from gemini at geminix.in-berlin.de 
(Uwe Doering) and tik at abqhh.hanse.de (Michael Havemester) I found two problems
with ISC's harddisk and floppy drivers (possibly not related to each other):

1st problem:
     When using certain motherboards and ET4000 VGA controllers together
     write accesses to the floppy disk(s) may fail, however these failures
     are not reported at all (invalid data will be written without notice).
     This happens frequently when mounting floppy file systems read/write
     (causing the whole file system to be destroyed) and less frequently
     when writing to floppy disks sequentially (e.g. copying disks).
     Since the `install' disk is a `mounted' file system and the install
     procedure writes quite a lot, installation of the OS fails 9 out of 10
     times because the install floppy gets destroyed (a *copy* of the install
     disk, of course ...).

2nd problem:
     If you connect two (!) hard disk drives to one (ore even two) `standard'
     AT type hard disk controller (i.e. MFM, RLL or ESDI drives) you may
     experience a `hanging' disk controller (making any further disk accesses
     impossible which possibly destroys one or more file systems) when both 
     disks are accessed concurrently (to reproduce this problem try to enable 
     an additional swap partition on the second volume, this will cause lots 
     of disk accesses on both disks when the system starts paging or swapping).

There seem to be no solutions to these problems, just some workarounds:

workarounds for 1st problem: 
   a) adjust `setup' parameters (DMA rate or bus clock may help a little bit
      but will probably slow down the machine)
   b) Michael told me this problem disappeared when he installed the ET4000 in
      an 8 bit slot; however this doesn't help much since Thomas Roell's
      X11 server requires a 16 bit path to the VGA controller
   c) don't *write* to floppy disks any more until a fix is available - reading
      floppys seems to work without problems (or, at least, verify *every*
      floppy you write - especially backup floppys!)
   d) try another motherboard (if you can afford buying new hardware each time
      some software fails ...)

workarounds for 2nd problem:
   a) connect only *one* disk to your system
   b) throw away your `standard' disk controller (and the disks connected to
      it) and get a SCSI controller and SCSI disk [a good decision anyway, but
      quite expensive if you already have two other disks ...]
   c) try another motherboard ...

[Personally, after having had to re-install the whole system at least 3 times
I finally decided to get a SCSI disk - which seems to have solved the 2nd 
problem.]

ISC seems to know about problem 1 since even my distributor in Germany told me
it might have to do with the ET4000 controller, however there seems to be no
fix.

Both problems did already appear under ISC 2.0.2, but the situation became
worse when I tried (and finally succeeded after several retries :-( ) 
to install ISC 2.2.1.

Is there anybody out there who is or was stuck with the same problems 
(and possibly knows how to solve them other than buying new hardware)?
Anybody at ISC listening?

-- Ralph-Diether
-- 
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    | Ralph-Diether Marzusch, Rehwinkel 2, W-2070 Grosshansdorf, Germany |
    | E-mail: marzusch at odiehh.hanse.de             Voice: +49 4102 64193 |
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