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DJGPP for PC-9801/9821 target
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jps...@gmail.com
Aug 12, 2020, 3:59:17 AM8/12/20
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Hey folks,
I know there are some mentions of the NEC PC-98xx as a target in various bits of (very) old documentation, but wondered if there was anyone who could confirm whether this is still supported, or if it has bitrotted and become unsupported since it was introduced?
If you're not aware, the PC-98 was a range of "sort-of" PC compatibles by NEC in the mid-late 80's and early 90's in Japan. The older 9801 used NEC Vxx processors and the later 9821 used x86 (386, 486 and Pentium), they shared a few bits of PC-like peripherals and ran a slightly modified version of MS-DOS and Windows, but had completely different BIOS interface, interrupts, memory map, sound and graphics hardware. Just like regular PC's, they were also immensely popular for running games :)
Well behaved DOS applications can run on them, but at an absolute minimum they would need a different crt0 as an output target, but likely other things too.
I was wondering if this was still a viable target?
I know there are some mentions of the NEC PC-98xx as a target in various bits of (very) old documentation, but wondered if there was anyone who could confirm whether this is still supported, or if it has bitrotted and become unsupported since it was introduced?
If you're not aware, the PC-98 was a range of "sort-of" PC compatibles by NEC in the mid-late 80's and early 90's in Japan. The older 9801 used NEC Vxx processors and the later 9821 used x86 (386, 486 and Pentium), they shared a few bits of PC-like peripherals and ran a slightly modified version of MS-DOS and Windows, but had completely different BIOS interface, interrupts, memory map, sound and graphics hardware. Just like regular PC's, they were also immensely popular for running games :)
Well behaved DOS applications can run on them, but at an absolute minimum they would need a different crt0 as an output target, but likely other things too.
I was wondering if this was still a viable target?
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J.W. Jagersma (jwjagersma@gmail.com) [via djgpp@delorie.com]
Aug 12, 2020, 8:19:33 AM8/12/20
to dj...@delorie.com, jps...@gmail.com
https://github.com/lpproj/djgpp-cvs.nec/commit/ff819a64c2265ea45675489b18d4cecd91b28e4b
I personally have no experience with PC-98, so I don't know how complete it is.
jps...@gmail.com
Aug 13, 2020, 6:37:50 PM8/13/20
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Well I managed to find a really old patch against 2.03 that adds in support for the PC-98xx.
It took a while to get a working environment - the patch was a partial binary diff against libc.a, which would work on the version of DJGPP that I found, so I had to bootstrap the whole thing from within Dosbox with a correct version of GCC (2.95.2, if you're interested!).
Finally got it all running and compiled binaries can run on both regular PC MS-DOS and PC-98 MS-DOS as long as you have a DPMI server for the latter (cwsdpmi wont work, quite obviously, but there's one by Microsoft, on the PC-98 DOS 5.00 floppies!!!).
Anyway, I can see there are a couple of efforts to get full support in current versions of DJGPP, but for now there's a pre-built Dec environment and how-to on my wiki:
https://www.target-earth.net/wiki/doku.php?id=blog:pc98_devtools
Next step is to work out how to talk to the custom NEC graphics hardware from within GCC+DJGPP...
It took a while to get a working environment - the patch was a partial binary diff against libc.a, which would work on the version of DJGPP that I found, so I had to bootstrap the whole thing from within Dosbox with a correct version of GCC (2.95.2, if you're interested!).
Finally got it all running and compiled binaries can run on both regular PC MS-DOS and PC-98 MS-DOS as long as you have a DPMI server for the latter (cwsdpmi wont work, quite obviously, but there's one by Microsoft, on the PC-98 DOS 5.00 floppies!!!).
Anyway, I can see there are a couple of efforts to get full support in current versions of DJGPP, but for now there's a pre-built Dec environment and how-to on my wiki:
https://www.target-earth.net/wiki/doku.php?id=blog:pc98_devtools
Next step is to work out how to talk to the custom NEC graphics hardware from within GCC+DJGPP...
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