[Linux-parport] Connecting 2 PCs directly over an "8-wire Fast Laplink" cable

Robert Heller heller at deepsoft.com
Mon Jun 28 14:15:03 EDT 2004

In message <20040628200224.A11439 at pc199.ben.tuwien.ac.at>, Daniel Tahin writes:
>Hello Developers!
>Hopefully I'm here right. I would like to ask you about connecing two PCs over
> a Laplink cable (on the paralell port). But this cable isn't a common Laplink
> cable that uses only 4 data lines; it uses each (8) data lines. Information a
>bout cross connecting the cable I put at "http://members.a1.net/e0226781/".
>It works well under Windows98, with 160-190Kbytes/sec (better than 50Kbytes/se
>c with the cable that uses only 4 data lines:-))). I would like to ask you, th
>at is really the highest transfer rate, that could be reached with it? (I ask 
>you, because I think other paralell devices can do a higher transfer-speed wit
>h 8 data lines? Or not?)
>I set the port to ECP, and EPP mode before doing any transfers, but I couldn't
> go over 190Kbytes/sec.

The parallel port is a master-slave type of interface -- it is NOT a
symetrical bi-directional device.  What happens with ALL of the
'Laplink' parallel port hacks is some sort of hack to 'fake' a full
duplex interface -- this by its very nature will reduce you effective
throughput.  With a 'normal' paralell device (eg printer), there is a
clear master (computer) and slave (printer) relationship and no need to
fake anything.

If you really need high-speed bi-directional data transfer, get yourself
a pair of EtherNet NICs (either PCI cards and/or PCMCIA cards,
depending).  These cards are cheap enough and easy to get (Radio Shack
sells them).  With a Cat-5 crossover cable you can skip the switch.

It might also be possible to get better thn 190Kbytes/sec. thoughput
with either FireWire or USB 2.0, but I don't know of any PC-to-PC data
transfer software using either FireWire or USB 2.0.

>Best regards, and thanx for your answer.
>Linux-parport mailing list
>Linux-parport at lists.infradead.org
Robert Heller                        ||InterNet:   heller at cs.umass.edu
http://vis-www.cs.umass.edu/~heller  ||            heller at deepsoft.com
http://www.deepsoft.com              /\FidoNet:    1:321/153

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