Hi.
What follows is not an answer; just an opinion that can be
completely wrong.
Take into account that in the early days the electronics
involved in the parallel port (and keyboard) were TTL
signals. TTL chips manufacturers only guaranteed things
working when PCB tracks were limited to 1 foot (30 cm). In
that sense the printer and the keyboard cables were out of
TTL specifications, but things worked, since in practice
(and in garage electronics) these things work.
So you can alleviate these 'out of specs' things working on
the cable (shielding, grounding and separation). More than
that, a cable is a cable and a digital signal is a digital
signal.
Now, although the TTL levels are maintained, the chips
involved are moreless customs, with input/output stages
probably with more driving capability than TTL chips. So
improvements could be on the electronics (say current
controlled instead of voltage controlled), but I haven't
heard of any significant invention in cabling. The only
thing would be more signal separation (to minimize mutual
capacity), and you should see this if the cable is thicker.
May be you see an ordinary $2-3 chinese printer 25 wire
printer cable and a "brand" one costing 20 times that; the
only difference may be how happy are the vendor and
manufacturer when selling one. It is usual that the PC
vendor sells a printer at his own cost, and his benefit is
the cable; of course he will say how wonderful it is.
So my advice is:
-Distinguish 18 and 25 wire cables through its thickness;
take only the thick ones (25).
-Individual shielding would make the cable much more thick,
so this should be carefully checked to be true.
-More signal separation would also make the cable thicker.
************************************
Javier Vizcaino. Ability Electronics. [log in to unmask]
http://www.automodelismo.com http://ability53.hypermart.net
Starting point: (-1)^(-1) = -1
Applying logarithms: (-1)*ln(-1) = ln(-1)
Since ln(-1) <> 0, dividing: -1 = 1 (ln(-1) is
complex, but exists)
----- Mensaje original -----
De: JMB <[log in to unmask]>
Para: <[log in to unmask]>
Enviado: miércoles 28 de abril de 1999 3:19
Asunto: [PCBUILD] IEEE1284 Cables
> Okay, you engineers out there, what gives?
>
> Now a days, when you buy any computer, you have to
separately purchase a
> printer cable and every manufacturer ALWAYS recommends a
bi-directional
> IEEE-1284 compliant cable.
>
> Well, for about the last 8 years, all printer cables were
bi-directional
> capable (at that time it meant that all 25 pins were
populated in the
> DB-25 connector and properly terminated in the matching
centronics
> connector.
>
> Somewhere along the way, manufacturers decided that a NEW
(read that as
> 4X more expensive) printer cable was required for all new
printers!
>
> Even the lowly Lexmark 1100, Canon BJC250, and Epson 440
'require' a
> bi-directional, IEEE-1284 compliant printer cable.
>
> So what is the difference between an IEEE-1284 and an
ordinary printer
> cable? Since both cables are shielded, the only thing I
can think of is
> that maybe the 1284 cable has each major signal wire
individually
> shielded, but I noticed that the cable diameter is almost
the same
> diameter as ordinary cable.
>
> So what exactly makes the 1284 better? I have used
'ordinary' cables on
> many low and mid-grade color inkjets with no degradation
in signal. I
> even used one on an HP-5000 for about 1 month until I
could obtain a
> 1284 cable, and observed no difference in print quality or
> computer-printer operation (errors and such). So what is
the big deal
> here?
>
> Any theories are greatly appreciated.
> --
> Jean Bourvic :>))
>
> PCBUILD's List Owner's:
> Bob Wright<[log in to unmask]>
> Drew Dunn<[log in to unmask]>
>
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