Posted By
TLC
on 2004-10-27
07:16:10
|  Re: X1541 cable and WinXP
SVS:
There are several different problems regarding either the parallel ports of the new(er) pc's or the operating systems (or both).
On the operating system's side: SC was originally designed for DOS. It simply needed the single task/single user environment for its realtime tasks. Later, async transfer modes were introduced that are mostly able to work even in a dos window of Win95 or '98 (they're less / not dependent on precise timing). With NT, 2k and XP there's another problem, however: these forbid DOS programs to use direct hardware access. With some utilities, it's possible, though.
The cables have more to do with the parallel ports. Back in the old days  most pins of the parallel ports, if not all were bidirectional. X1541 depends on this feature. Later, the pins used in the X1541 cable became unidirectional, that's why the X1541 mostly won't work on anything later than different P1 models, in any parallel port modes. XE1541 was introduced as a work-around for this.
Someone then figured out (I don't remember the author) that it could be possible to make the 1541 handler at least partly interrupt driven, and for that, he modified the XE1541 so that the CLK line will be connected to a pin that can generate interrupt requests. This is XM1541.
Finally, there were parallel ports that were "weak" in the electronic sense so they can't even sufficiently drive the 1541 serial bus. For those, the XA1541 was introduced. (In these, the lines are driven by transistors; in previous cables, the active components are schottky diodes).
So... If your computer was physically able to drive an 1541 with an X1541 cable, then you could use that one, after you "hacked" the XP to allow SC to see the parallel port. (But I'm afraid, it's not).
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