The parallel ports are presented by three areas in the I/O space.
- Area#1 (here 6400-6407)
- represents the parallel port. This can be changed
by the mechanisms available in Windows9x.
- Area#2 (here 6500-6507)
- is necessary to operate the port in EPP-mode. The
necessary configuration registers are located here.
- Area#3 (here 6600-661F)
- represents the card interface itself.
Never change this item.
The changes are permanent, even after a reboot. Until the box of "automatic settings" is checked again.
Sometimes it may be useful to change the base addresses. In very rare
cases old DOS programs may require this.
Also some device drivers may require to find the parallel port at a
"standard address". The only addresses usable by this software are 0378h
and 0278h. It is forbidden to use 0278h on PCI cards. This will
instantaneously cut off the ISA Plug&Play opportunities. The only way
out is to change the parallel port on the mainboard to 0278h, and use 0378h
for the PCI port range#1. To operate the port as EPP, it is required to
set the range#2 at 0778h, i.e. range#1 plus 0400h.
Also some hardware may require changing the address. This includes printers,
dongles, scanner, external drives, and others more. We suggest not to
change the address. Instead a better driver from these manufacturers should solve
the problem.
This is an example of successful changed address. However even a successful change
does not guarantee operation of the port.
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