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Doubts about DOSBOX possibilities with LPT ports

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First post, by KeiDash

Posted on 
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Hello! I'm new here and I've registered because an old hardware issue that I have. The reason of my question it's because I don't know if is possible to do that I want.

I'm try to read something about this issue but I'm not found anything about this (meybe because It doesn't exists or I'm not able to find that)

The main question is:

It's possible use a host LPT PORT in dosbox?

I have an old device that only works on Windows 98 using the mother board parallel port. This is not a printer but I think that use the parallel port like "serial port" to transfer data between PC and this hardware. I tried to use this hardware using a PCI parallel port board and Virtual Machines like VMWare or Virtual Box. This softwares recognices my host COM ports but when I try to use the sofware in this VM that connect with my old hardware, they doesn't found the hardware, so, when my friend told me about this forum, I thought that "maybe here is possible"

At this momment I solved it using a real hardware with Windows 98 but this is a little uncomfortable because I must have change between computers to read and write data in this old hardware.

So, it's possible? In this case, exists any documentation to read how to do that?

Thanks!!

Reply 1 of 3, by Jo22

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Hi there!

Parallel Port support is difficult to implement.
Especially on Windows, which doesn't even have an official API to access LPT ports (unlike RS232 "COM" ports).

Another issue is, that there's no single LPT port.
There are several different types, actually.

Centronics (from the 80s), Standard Printer Port (SPP), PS/2 Mode, Nibble Mode, EPP, ECP..

https://en.wikipedia.org/wiki/Parallel_port

What you're looking for is a pass-through feature.
To directly access the physical parallel port from within DOSBox.

To make that work (on Windows), DOSBox would have to directly talk to hardware, which
was allowed in DOS-based Windows versions, but not Windows NT anymore.

It's not impossible, though, if a driver like PortTalk was used on Windows NT.
It would allow these things like on Windows 98.

However, that's against the conventions and would make DOSBox non-platform independent.
Because, it would need to make direct port accesses. Windows has no LPT API, after all.

Edit: Microsoft Virtual PC 2004/2007 did support LPT pass-through.
I checked that feature myself in a DOS VM about ten years ago.
VPC has its own sets of drivers that integrate into Windows.

Edit: DOSBox-X may support such things, not sure.

Edit: Just checked your link. Cool! 😎
I've had a similar device, by the way - the vintage gb e-merger for backing up cartridges. Used parallel port, too.

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 3 of 3, by Jo22

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You're welcome. ^^

Virtual PC 2007 did work for me, as I said earlier.
Maybe VPC can be somehow made work on modern Windows ?
It can run Windows 98SE in a VM very well, too.
VPC 2007 had both x86 and x64 executables and optional patches/updates for download.

Edit: I've taken a picture of VPC for you..
Sadly, the PC is a Mac Pro and has no LPT port installed right now.
If it had, you'd see LPT1 being mentioned for selection.

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"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

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