DOS extenders

[T. Ment]

While looking at Causeway I also found PMODE. It's small, lacks support
for virtual memory. That mattered when PCs only had 4 meg, but it's hard
to find those on Ebay now. And the price is high if you do.

Wikipedia says

The source code to PMODE/W was never made available to the public

but that is false http://www.sid6581.net/pmodew/

The source looks simple, only two .asm files, and a 3 line batch build
file that calls tasm and tlink.

Any comments or opinions about PMODE? Causeway? others?

[JJ]

Post by T. Ment
While looking at Causeway I also found PMODE. It's small, lacks support
for virtual memory. That mattered when PCs only had 4 meg, but it's hard
to find those on Ebay now. And the price is high if you do.
Wikipedia says
The source code to PMODE/W was never made available to the public
but that is false http://www.sid6581.net/pmodew/

Wikipedia is not wrong considering that the article was last updated on
March 9 2018. The PMODE/W source code has not yet been released at that
time. It was only released on September 19th 2018.

Perhaps you might be interrested of being the one to update the article with
that important information.

[T. Ment]

Post by JJ
Wikipedia is not wrong considering that the article was last updated on
March 9 2018. The PMODE/W source code has not yet been released at that
time. It was only released on September 19th 2018.

Right then wrong now.

Post by JJ
Perhaps you might be interrested of being the one to update the article with
that important information.

Too low on my priority list. It's fine if someone else does.

[Kerr-Mudd,John]

Post by T. Ment

Post by JJ
Wikipedia is not wrong considering that the article was last updated
on March 9 2018. The PMODE/W source code has not yet been released at
that time. It was only released on September 19th 2018.

Right then wrong now.

Post by JJ
Perhaps you might be interrested of being the one to update the
article with that important information.

Too low on my priority list. It's fine if someone else does.

removed "never"

[Rod Pemberton]

On Sat, 12 Oct 2019 15:10:27 +0000

Post by T. Ment
Any comments or opinions about PMODE? Causeway? others?

I use the DPMI hosts that come with the C compilers I use. I also have
a large collection of others to which I can test with, but I'm aware
of just about as many that I don't have. Most DPMI hosts mostly comply
with DPMI 0.9. There are only a few DPMI 0.9 complete hosts of the ones
I've tested (about 2 out of 3) in my collection (Windows 98/SE, CWSDPMI,
QDPMI, DPMIONE, HDPMI). There are only two DPMI 1.0 hosts that I'm
aware of (DPMIONE, HDPMI), but I haven't checked some hosts.

My experience with the PMODE variants below is that they're fast and
reliable, but one (or maybe both?) doesn't use paging. Unfortunately,
some special functionality was added to CWSDPMI to allow piping of DOS
commands between DJGPP applications, which isn't available for
PMODEDJ. So, you can use PMODEDJ for DJGPP apps, but you can't use it
to compile with (since the C compiler uses extended piping) or for apps
that use DJGPP extended piping.

OpenWatcom: DOS4GW, PMODEW
DJGPP: CWSDPMI, CWSDPR0 (Ring-0), PMODEDJ (aka PMODETSR)


Rod Pemberton

[T. Ment]

Post by Rod Pemberton
My experience with the PMODE variants below is that they're fast and
reliable, but one (or maybe both?) doesn't use paging.

With enough memory, I don't need paging. It's slow anyway.

[r***@gmail.com]

Hi,

Post by T. Ment
While looking at Causeway I also found PMODE. It's small, lacks support
for virtual memory. That mattered when PCs only had 4 meg, but it's hard
to find those on Ebay now. And the price is high if you do.
Wikipedia says
The source code to PMODE/W was never made available to the public
but that is false http://www.sid6581.net/pmodew/
The source looks simple, only two .asm files, and a 3 line batch build
file that calls tasm and tlink.
Any comments or opinions about PMODE? Causeway? others?

I knew it was available (for commercial purposes) but didn't know
the source had been released. Still cool, even though I haven't
looked at the licensing yet.

AFAIK, it only accesses 64 MB of RAM, so it's a bit limited. But
still good for "smaller" programs. (UHarc compressor from 2005
[DOS version, obviously] used it.) You can probably override
it with "cwstub uharc.exe". Causeway does support virtual
memory (swapping), unlike PMODE/W, but it's slow. (Unlike
DJGPP, which only uses 3 MB if you only need 3 extra MB,
Causeway will swap the *entire* amount out. Oh, and OpenWatcom's
malloc is less efficient than DJGPP's.)

* https://www.sac.sk/download/pack/uharc06b.zip
(7-Zip is probably better overall these days. Still, it's cool.)

[r***@gmail.com]

Hi again,

(Unlike DJGPP, which only uses 3 MB if you only need 3 extra MB,
Causeway will swap the *entire* amount out. Oh, and OpenWatcom's
malloc is less efficient than DJGPP's.)

Minor correction, obviously I meant "CWSDPMI" here. DJGPP 2.05
(IIRC) also switched malloc (again) to CBFalconer's nmalloc.
I think it's faster for lots of frees, otherwise dunno if it's
more efficient or not. I'm thinking more of older 2.04 vs.
OpenWatcom (my compiles of Matt Mahoney's paq8o8). Also,
CWSDPMI r7 (circa 2010) did add 4-MB pages support, which
I'm not sure can be swapped out, but it's noticeably faster,
when supported. (It can be disabled with CWSPARAM.)

Oh, here's a historical page with details about DJGPP's malloc:
* http://www.delorie.com/djgpp/malloc/