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No more Parallel/Serial?


2006/12/27

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 docsrv.sco.com:507/en/OSAdminG/prntT.slowParallel.html (link dead, sorry) ways to control that and other printing oddities. I do not know if you can control polling in current Linux: http://www.novell.com/documentation/suse91/suselinux-adminguide/html/ch06.html 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: http://www.beyondlogic.org/spp/parallel.htm (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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© Anthony Lawrence







Wed Dec 27 15:30:30 2006: 2783   BigDumbDinosaur


All of our (Athlon64 powered) workstations come with a parallel port and at least one serial port. USB is not the ideal medium for printing, in my opinion, and downright sucks for serial port applications.

As you noted, the parallel port is seldom used anymore with a server. The two types of Opteron dual and quad processor motherboards we use in our servers do not ship with a parallel port and we haven't really found that to be a problem. The boards we use all have two serial ports, however. We always connect a UPS's data link to the server via the serial port (usually COM2) -- never to the network. Therefore, at least one serial port is essential. We will continue to provide serial ports on our servers as long as the motherboard manufacturers continue to make them available.



Wed Dec 27 22:57:27 2006: 2784   drag


I love using some ancient laptop as a serial console. I used one for a long long time until I ended up giving it to my mom for some word proccessing stuff she wanted to do. (I should get it back!) Used kermit on MS-DOS. It was a very old machine, 8 megs RAM.

What would it take to use USB for serial console? I looked at it a bit, but it's confusing.

The cool thing about that is that it would be perfect for handling multiple headless servers and such.. Setup a very secure old laptop that would act as the front end, have a couple USB hubs, and then you can have lilo output to the console. No need to have ssh or any sort of remote access directly to the servers and the laptop can grab information from the kernel logging output to the console and save it to a file for debugging purposes. You could have a dozen servers for each laptop front end, and with laptops being very cheap nowadays it just makes sense to me.. it's as cheap as those fold down rack mount monitors you can buy.

I know how frustrating it is to have a server 'just let go' for some reason and you have no idea why it rebooted or crashed or whatnot. Having saved console output would probably be very helpfull.

But I don't know how you'd go about doing something like that. It seems nice on the front of it.


And on a side note Usenix conference from last year had a presentation for 'legacy free' servers. They developed a PCI card that took 'legacy' O/I such as VGA, keyboard, serial, parrellel, etc etc and encasulated it in IP so that you could setup a workstation on a network to grab that I/O over the network. This is for installing and managing operating systems and such without having to actually have to physically access the hardware. (Google was very interested)



Fri Feb 16 19:57:32 2007: 2864   TonyB


The particular printer cable you were talking about used to cost about $25.00. I still have it. I had the tandy 286 version (can't remember the name). Back then (1987) PC's ran close to $1000.00. My how things have changed.....

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