[Linux-parport] parport_pc disables Hercules mode of mdacon on one pentium

Adam Baker parport at baker-net.org.uk
Thu Jul 22 16:36:42 EDT 2004

On Thursday 22 July 2004 02:48, Sindi Keesan wrote:
> I was able to get the third computer to work by NOT insmod'ing the
> parport_pc module.  Load all the modules manually and mdacon works
> properly with parport_pc, but then I load parport_pc and the Hercules mode
> goes bad again.  It does not help to load mdacon before rather than after
> parport_pc, or to rmmod parport_pc after the problem occurs.
> The fix is either not to use mdacon at all, or to insmod parport_pc
> manually only when needed for printing, after first switching to a VGA
> terminal.  Then I need to reboot (into DOS and then again into linux) to
> use both monitors.  I don't often print in linux.
> Slackware 7.1, 2.2.16 kernel (specially compiled with minimal drivers for
> Basiclinux 2).  I have not tried a different Hercules card in there, or a
> different kernel (bare.i, for instance, which I think has parport_pc built
> in).
> My theory is that mdacon and parport_pc are using  the same RAM on that
> computer, if that is possible.  Another computer will not work at all with
> Hercules cards due to RAM conflicts of some sort, I think.
> Is there some way to specify where in RAM to load a module?
> Would it help anyone if I were to try a different Hercules card or a
> different kernel and report back?
My theory would be that it is the probing for possible parallel ports that is 
causing the problem, I assume the hercules cards are old ISA cards and hence 
may well have a register that is at a location typically used by one of the 3 
standard parallel ports. My first suggestion is therefore to specify when 
insmod'ing parport_pc the io address to use which should prevent other 
addresses from being probed. It is also worth seeing if the problem follows 
the card if you move it between machines.

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