No more Parallel/Serial?
The last few servers I configured for customers have no parallel ports, and the new laptop I just bought for my wife doesn't have one either. Both the customers and my wife were surprised, but I wasn't: almost all printing today in business is networked, and home class printers are usually USB only. Parallel is disappearing quickly.
The new servers still had at least one serial port, but my wife's laptop doesn't have that either. It does have a built-in modem - probably because so many home users still use dial-up internet. The USB ports can easily be used as parallel or serial ports if you need to support legacy devices, so there's just no need to waste the space or the expense.
Memory lane: ancient Tandy printers required a special cable.
Some cheap parallel ports didn't handle interrupts well: SCO had
(link dead, sorry)
to control that and other printing oddities. I do not know if
you can control polling in current Linux:
seems to imply that you can, but http://people.redhat.com/twaugh/parport/
says polling is unimplemented.
Many years ago I wrote a parallel port driver because I was having trouble getting a particular
printer to work. I put all sorts of debugging and control code into the driver but oddly never needed it: the printer started working correctly the moment
I installed my driver. Still, writing the code was fun:
(link dead, sorry)
has the sort of details I didn't have back when I
did this, but it wasn't all that difficult.
It probably won't be too many more years before parallel and serial ports disappear entirely.
PCI Parallel ports
If you absolutely must have a parallel port (I don't know why, because you with any Unix system, see How can I make a device that will print to a network printer?), you can usually use a PCI parallel card, BUT you are less likely to have trouble if you choose one that claims "exactly replicates a legacy LPT port" or "fully DOS compatible".
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