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Fastest Parallel port card

E

evildragon

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What is the best parallel port card I can get for my model 25?

I'm ready to sacrifice the SoundBlaster in it, for a better parallel port card, so my external hard drive goes much faster.
 
I presume that the existing parallel port is at least bi-directional.

The next step up would be EPP. EPP improves the handshake between the machine and the device, increasing the speed of the transfer. I've run EPP ports on a PCjr.

ECP would be the top of the line, but these require DMA which might be tight on your system. (It is effectively an XT, so there is not a lot to go around.)
 
The port on my model 25 is reported as uni-directional according to my hard disk driver, and the 20kbps file transfers via ftp are getting old now fast..
 
At one point I was under the impression that all PS/2 parallel ports were bi-directional. Apparently that is not the case ..

What we really need is an 8 bit ISA card for "limited" machines that includes XT-IDE and Ethernet. :)
 
XT-IDE was nice, but the fact I have to make it myself, forget it, I don't even have an EEPROM burner.

I can't find a single EPP parallel port card that would work on XT's at all, like they don't exist.
 
The Model 25 has a bidirectional printer port; it just doesn't work the same way that the other (higher) models do. According to the Model 25 Technical reference:

To allow the parallel port to receive data from external devices, disable the output buffer by writing a 0 to bit 7 of the System Board Control register.
Click to expand...

This is a bit different from the other PS/2 models, which use bit 5 in the printer port control register to change the direction. This is port 65 (hex) and is configured thus:
Code: 
Bit  Function 
7  Parallel Port Output Enable 
6  Reserved  =  0 
5  Reserved  = 0 
4  Serial CS 
3  Diskette CS 
2  Video CS 
1  Parallel Port CS 
0  Fixed Disk CS

So, you'd read port 65H, then clear bit 7 and write the byte back to enable input.

The PS/2 TRM for the Model 25 is on bitsavers.
 
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evildragon said:
I can't find a single EPP parallel port card that would work on XT's at all, like they don't exist.
Click to expand...

Actually, almost any simple printer port (that uses simple SSI TTL) can be changed to provide EPP with a cut and jumper, including most cheap Taiwanese boards as well as both the IBM printer adapter and the IBM MDA.

It's been discussed here.
 
Hmm ... I'm confused (again).

My understanding of the bi-directional parallel port is that an LS374 is usually wired to always output data, not to read it. The modification on the MDA card and similar designs (including the PCjr parallel port sidecar) is to put the LS374 under software control such that it can be told to both read and write.

What does that bit on the "System Board Control Register" do - does it just enable/disable the write to the control port on the parallel port to change the direction of the LS374 (or equivalent) ?
 
mbbrutman said:
What does that bit on the "System Board Control Register" do - does it just enable/disable the write to the control port on the parallel port to change the direction of the LS374 (or equivalent) ?
Click to expand...

Well, the parallel port always is in input mode, so you just tristate the output buffer (374). The thing with the 25 is that the control bit was moved to bit 7 of port 65h. Don't ask me why--I don't know. But writing that bit has the same effect as writing bit 5 in the "normal" EPP control register.

Too bad that not many software vendors knew about it.
 
Chuck(G) said:
Well, the parallel port always is in input mode, so you just tristate the output buffer (374). The thing with the 25 is that the control bit was moved to bit 7 of port 65h. Don't ask me why--I don't know. But writing that bit has the same effect as writing bit 5 in the "normal" EPP control register.

Too bad that not many software vendors knew about it.
Click to expand...

That seems like a case of criminal stupidity ...

On a normal parallel port the control register for the port is at the base address + 2, and it's the 5th bit in that port that controls pin 15 on a 174 , which can then be used to control the 374. Moving that bit to port 65, bit 7 makes no sense at all, and no wonder why nothing that checks for a bi-directional port on a Model 25 can detect it ...

Thanks for clearing that up.


Mike
 
So then literally the only thing would be to either find a way to modify the driver to access it correctly (it's a .sys driver in config.sys), or just get a new card.

As for SCSI, I don't have any enclosures and would rather an extra parallel port anyway..
 
Hmm, any takers on modifying the driver for me? Or teach me how its done. Sounds like its just one hex string that needs to be changed.
 
It may just be a fluke, but yesterday i picked up an 8 bit serial/parallel/game port card. Its brand new in box, the shrink wrap is still sealed. I got it because it was sealed and $10. It "features" a bi-directional printer port and claims it will work in any AT compatible slot. Its made by Siig, whom I believe are the best at what they do. Model IO1802. Google brings up nothing of value on a search. I have a late model Siig card that has 16550 uarts in my 386 and it can easily saturate the isa bus with just the hard drive...

Its one of those things thats just going to sit on my shelf and look pretty, let me know if your interested.
 
Chuck(G) said:
Actually, almost any simple printer port (that uses simple SSI TTL) can be changed to provide EPP with a cut and jumper, including most cheap Taiwanese boards as well as both the IBM printer adapter and the IBM MDA.

It's been discussed here.
Click to expand...

Chuck,
I've made this mod on a parallel port and it works well, but I found one downside. If the port is in input mode when a cntrl-alt-del is executed, the port is not recognized upon boot and the only way to recover is to cycle the power since my 5155 doesn't have a reset switch. Do you know of a solution for this problem? If I short the "Power Good" lead to reset, will the parallel port be reset?
 
Well, essentially you want to clear the control port on RESET. What kind of parallel port (i.e. what's the IC lineup?) do you have?

Failing that, you could tweak the BIOS to make sure that the control port is cleared in the parallel port test code or you could even install a TSR to hook INT 19H and clear on the three-finger-salute.
 
mbbrutman said:
That seems like a case of criminal stupidity ...

On a normal parallel port the control register for the port is at the base address + 2, and it's the 5th bit in that port that controls pin 15 on a 174 , which can then be used to control the 374. Moving that bit to port 65, bit 7 makes no sense at all, and no wonder why nothing that checks for a bi-directional port on a Model 25 can detect it...
Click to expand...

I think in this case it was grouping the "planar features" of the Model 25 and Model 30 to one control port. Certainly it is unique, and very proprietary. Code that would sync the two bits would avoid the matter entirely (as I recall, the parallel and serial ports of the Model 25 and 30 are locked in place anyway, I even think it is at the odd 03BCh address).

Your confusion might be from the early PS/2s, where all microchannel systems had base 16650 UARTs, and ISA models were limited to 16450s. All of the parallel ports were bi-directional, with the caveats of this thread. I wonder if the parallel-based "Data Migration Facility" had extra code to account for if it was run on a Model 25 or 30.
 
Chuck(G) said:
Well, essentially you want to clear the control port on RESET. What kind of parallel port (i.e. what's the IC lineup?) do you have?

Failing that, you could tweak the BIOS to make sure that the control port is cleared in the parallel port test code or you could even install a TSR to hook INT 19H and clear on the three-finger-salute.
Click to expand...

It looks like a generic parallel card similar to the original IBM 8bit card. I disconected pin one of the 374 from ground and jumpered it to pin 15 of the174. Next time I have the card in my hand I'll take some hi-res pics of it and post them here. I'm afraid that "tweaking" the bios is currently beyond my ability but if someone else would like to give it a try, I'll help in any way I can.
 
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Pin 1 of the 174 is the CLEAR input and is normally connected to the RESET bus signal (position B02 on the ISA connector). (The 5150 Tech Ref has the legends for the 174 pin 1 and 9 swapped and is wrong).

So a TSR to hook the three-finger salute may be in order. It should be very small.
 
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