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Parallel Cable File Transfer DOS PCs

IBMMuseum said:
With some older systems, receiving files might be more hardware-dependent than the DOS version: The bi-directional printer port ("EPP" now, but initially know as a PS/2 parallel port) has to be present, and there isn't any mechanism to drop down to a "nibble" mode if not. All PS/2s had bi-directional parallel ports (a few third-party adapters specifically for them did not), and the microchannel level (Model 50 and above) had 16550-level UARTs (again, some adapters were 16450).
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Very related...

One of the "hacks" that's been largely forgotten is that both the IBM Parallel port adapter and the Monochrome/Printer adater can be modified with nothing more than a cut and jumper to provide EPP bidirectional capabilities. In both, IBM used a 74LS174 Hex flip-flop to provide all of the control signals on the printer interface. In addition, both provided an LS240 receiver to monitor the state of the parallel port. Since there are only five control signals, the sixth flip flop is left unused on both, even though it is connected to bit 5 on the data bus.

So it's a simple job to lift pin 1 on the LS244 latch U3 on the parallel adapter (or OE/ on the LS374 latch, U41 on the MDA) and jumper it to pin 15 of the LS174 (U7 on the parallel port adapter or U39 on the MDA) and you've got yourself a PS/2-conforming bidirectional printer port. Like the PS/2 port, bit 5 of the control port, if set to 1, puts the parallel port into input mode. Many of the cheap Taiwanese printer adapter cards can be modified in the same way.

Another mystery of "Why didn't IBM do that?"

FWIW, somewhere on SIMTEL, I think, there's an old program of mine called LPTGPIB or something like that that used the 5150 parallel port to drive an HPIB-interface 5-pen HP plotter.
 
PeterNY said:
Unfortunately I have no reference disks...
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We thought ahead: The required "receiving" executable has a link from the referenced page...

EDIT, before I had to: Thought ahead but, duh, someone hard-coded the file's location assuming it wouldn't change through time (and it did). Correcting it now. Give me ten minutes.

EDIT: Now fixed, refresh the page...
 
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Chuck(G) said:
Very related...

One of the "hacks" that's been largely forgotten is that both the IBM Parallel port adapter and the Monochrome/Printer adapter can be modified with nothing more than a cut and jumper to provide EPP bidirectional capabilities. In both, IBM used a 74LS174 Hex flip-flop to provide all of the control signals on the printer interface. In addition, both provided an LS240 receiver to monitor the state of the parallel port. Since there are only five control signals, the sixth flip flop is left unused on both, even though it is connected to bit 5 on the data bus.

So it's a simple job to lift pin 1 on the LS244 latch U3 on the parallel adapter (or OE/ on the LS374 latch, U41 on the MDA) and jumper it to pin 15 of the LS174 (U7 on the parallel port adapter or U39 on the MDA) and you've got yourself a PS/2-conforming bidirectional printer port. Like the PS/2 port, bit 5 of the control port, if set to 1, puts the parallel port into input mode. Many of the cheap Taiwanese printer adapter cards can be modified in the same way.

Another mystery of "Why didn't IBM do that?"...
Click to expand...

I've found an 8-bit adapter using the common "SSP" 16452/16452 chip that wasn't easily wired (pin 1 tied high or low changed LPT/EPP mode) for bi-di...
 
Agent Orange said:
There are all kinds of serial pc to pc programs to be had for free if you take a little time to Google. You should still be able to get the adapter or null modem cable at Radio Shack or any computer outlet.
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From memory null modem takes forever so parallel really is the way to go. :D​
 
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Agent Orange said:
Well, it's a cheap way to go and its not like he's going to be transfering files all day every day is it?
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I think 'free' (Chuck) or 0.99 (eBay) for a parallel cable is actually cheaper and it is indeed faster... ;-)

The one advantage of the null-modem serial connection is that the "client" can be remotely installed from the "server", very handy if you have incompatible (or no) diskette drives and no other way to get a file on to the client in the first place.
 
IBMMuseum said:
Depending on location, I think nowadays you would just get blank looks from the "staff" (a 19 year-old kid)...
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Sure: most folks in regular retail stores no 0 about anything these days. And knowledgable storekeepers go out of business since there is no way to compete with large chains.​
 
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MikeS said:
The one advantage of the null-modem serial connection is that the "client" can be remotely installed from the "server", very handy if you have incompatible (or no) diskette drives and no other way to get a file on to the client in the first place.
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True. I vaguely remember one of my friends connecting to my 80286 back in 1992 or 1993 to transfer data from his 80386 without hooking up the monitor or keyboard. :)​
 
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MikeS said:
The one advantage of the null-modem serial connection is that the "client" can be remotely installed from the "server", very handy if you have incompatible (or no) diskette drives and no other way to get a file on to the client in the first place.
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Yes. A procedure for that, using Laplink 3, is at http://members.dodo.com.au/~slappanel555/transfer/transfer.htm

It requires a serial Laplink cable, and once Laplink 3 has been transferred to the second computer via that cable, then if desired, a parallel Laplink cable could be used to do the subsequent file transfers.
 
FYI: in case you own a license but misplaced the disk I can send you a ZIP with FastLynx 2.01.
 
IBMMuseum said:
Depending on location, I think nowadays you would just get blank looks from the "staff" (a 19 year-old kid)...
Click to expand...
You are right - you need to know what you are looking for. However, I did manage to get a null modem cable from my local RS not that long ago.
pRS1-7086393w345.jpg
Item nunmber 26-1141 ($11.99)
 
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