Re: old X, new 1.4.1pre

[Ignatios Souvatzis <is%jocelyn.rhein.de@localhost>]

On Sun, Aug 15, 1999 at 12:41:28AM +0200, Ignatios Souvatzis wrote:
> On Sat, Aug 14, 1999 at 11:20:34PM +0200, ali (Anders Lindgren) wrote:
> > off topic: I'm looking into plip, which seems be available
> > in port-i386. I've never written any kernel- or IP code --
> > would it be too difficult for me to have a go at it without
> > previous knowledge? I want to connect my newly acquired
> > (I'm not joking :-) ) 486 to my amiga, and plip seems 
> > like the most attractive solution.

> Amiga-PLIP is different from i386-PLIP. You lose, unfortunately.
> 

As Ali was quite astonished:

Intel-PLIP was developed for the original unidirectional parallel ports.
the 4 control lines on the chip were freely programmable and used as inputs
for PLIP.

The Amiga parallel port uses an intelligent chip, that a) is bi-directional
and b) does automatic handshaking (to a certain degree). The result of b) is
that one of the 4 control lines is NOT freely programmable as input, but can
only be used to create interupts when a transition occurs.

This is no problem for Amiga-PLIP, which uses the 8 data lines bidirectionally
and uses the a few of the control lines to negotiate transfer direction and
the handshaking lines to do handshaking. But the side effect is that
Amiga-PLIP and intel-PLIP can not, and never will!, interoperate. For hardware
reasons. 

(Of course it should be possible to write a Amiga PLIP for the modern PC 
printer ports (ECP), which are bidirectional. But this would be different
from Intel PLIP.)

If you want to write any of this, feel free.

Regards,
        -is