On Sun, 22 Dec 1996, John Payson wrote:
> Do you (or does anyone) have any idea whether that wierdness is only a
> problem with Toshiba laptops, or if it is more widespread?  I have no
> real qualm with the /Strobe wire not being open-collector (if it's open
> collector it will pose a bottleneck when trying to send data quickly to

This proves not to be the case.  That interface was designed in the early
days of TTL, and is designed to have a pull-up that is by modern standards
an awfully small value - I recall 220 ohms or 330 ohms as being common for
plain-old-TTL pullups.  And in fact, the Centronics interface was spec'd
with setup and strobe (minimum) pulse width on the order of a couple
microseconds not for the sake of the logic gates but to allow for a
reasonably long cable.

> [btw, even for the strobe wire, they should have done something analagous
> to the 87C51 pullup design: make it so that when the pin has a low->high
> transition it will be pulled up hard, briefly, and so that it's pulled up
> weakly the rest of the time.]

That would have been interesting, but I'm afraid you're forgetting how old
the design is.  They used an earlier design paradigm's "hard" pull-up
rather than one that hadn't been invented yet.  :-)