CH>NT defaults to polling, I would imagine that any printer and drivers,
CH>postscript, bidirectional, whatever, that work in NT 
 JG> could not be trying
CH>to use direct interupt printing as NT doesn't allow 
CH>direct hardware access
CH>of the printer port. Not sure about ECP ports, but 
 JG> those are a superset of
CH>the original PC parallel port architecture in that 
CH>not only do they have a
CH>hardware interupt, but they also use DMA. I don't 
 JG> know how NT handles ECP
CH>ports if it even does treat them differently from the standard IBM PC
CH>architecture paralell port. --- Maximus/NT 3.01b1
 JG> I've had problems with my HP5L if the sound card is set to IRQ7 with
 JG> bidirectional support enabled in the printer driver.  
 JG> That doesn't necessarily
 JG> imply that bidirectionality forces use of the interrupt 
 JG> but it appears to do
 JG> so in this case.
I -think- that depends on how you have your printer port hardware setup. If 
you set it to SPP (Standard Parallel Port), then the interupt is not held 
high and can be shared. If you are setup as ECP (Enhanced Centronics Port) 
then you cannot share the interupt, that seems to be inherrent in the design 
or the BIOS of computers supporting ECP ports. This is true of DOS, W95, 
whatever. If you use a Bi-di cable with a standard parralel port, then that 
would depend on the printer driver and the OS you are using. It makes sense 
that the windows drivers (W95 and W16) would have to hold the irq line high 
with printers that are capable/require BI-DI printing. It's a wild and wended 
path we weave with printer ports and interupts. I believe the only way you 
want to share printer port interupts with any other device is if you are 
running an SPP port configuration and are using non bidirectional printing.
Could be that NT doesn't support the "Windows printing system" (Some Canon 
and some HP printers use this in W16 and W95 and are not supported in Win NT 
and probably never will be) which is bidirectional with the IRQ line held 
high because it doesn't allow direct access of the ports and designing bi-di 
printer drivers for NT just ain't worth the hassle. NT doesn't appear to have 
support for ECP printer ports, but seems instead to treat them like ordinary 
SPP ports. I could very well be wrong about that though.
But it's not an important enough of a subject that I have wasted too much 
time researching. Some hardware freaks really get off on ports, I don't. Like 
you, my results and "theories" are primarily empirical.
I wouldn't really know if Mark is right/wrong. Usually he is right though. If 
he is wrong this time, I guess we can cut him some slack .
--- Maximus/NT 3.01b1
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