On Wed, Jan 9, 2013 at 3:38 AM, dmccunney <dennis.mccun...@gmail.com> wrote:
> On Wed, Jan 9, 2013 at 2:32 AM, Michael Robinson
> <plu...@robinson-west.com> wrote:
>> A protected mode dos like the one under Windows 9x and Windows ME
>> could be interesting and would justifiably deserve a different name
> I wouldn't call that a "protected mode DOS".  Win98/ME used DOS as a
> real mode loader for Windows.  The protected mode portions were in the
> Windows code, and once Windows was loaded, DOS was out of the loop.

I thought WinME removed the real mode bootup, hence lower compatibility?

Anyways, sure it preempted various DOS things, but other parts were
still used behind the scenes. It probably just switched modes a lot
(similar to DOS extenders). Indeed, I don't think it would run without
DOS, even if you did manage (somehow) to bootup without it.

>> Gates made some very bad assumptions ... nobody will ever
>> need more than 640k of memory for executable programs
>> and drivers...
> That wasn't a Gates decision, it was an IBM decision.  The 8088 CPU
> used by the original PC had a one megabyte address space.

Rumor is that IBM wanted 512 kb limit but MS complained! So we should
be grateful!  ;-)

Tim Paterson successfully used the full MB of RAM on his original 8088
clones. Even MS had some of those machines for a long time so that
they could "link the[ir] linker".

Besides, you could still use more (kinda sorta) via EMS. It was many
years before extended RAM was cheap and common enough for software to
be useful over 1 MB.

BTW, yes, vanilla MZ .EXE files are limited to approx. 640 kb, but
obviously various DOS extenders have worked around that by manually
loading the images themselves (via stub), hence why we have various 10
MB .EXEs in DJGPP ports (just FYI).

> Given that you have a megabyte available, total, and some *will* need
> to be reserved for the system, where *do* you draw the line?

Tegra 2 reserved part of its total RAM (address space) for the
graphics. A lot of other integrated chips / SoCs or whatever do too.
This is also why XP (32-bit) allegedly can only use 3.1 GB of RAM.
There are always hardcoded limits in everything, it's unavoidable.

>> Actually, there is OS/2 which was supposed to be the competitor to
>> Windows 9x and I'll bet that IBM is willing to release source code
>> to it.  Maybe the freedos community should get it's hands on OS/2
>> and develop it further.
> If IBM is willing to release code, that's news to me.

No, they've said at least twice, very openly, that they will never do
so. Besides, lots of the code is copyrighted by MS still (due to the
1.x co-development), so that makes it all the more complicated. IBM
just suggests people migrate to Linux and/or Java these days.

> You can still get OS/2 from an outfit called eComstation:
> http://www.ecomstation.com/product_info.phtml

Yes, it sells a 5-pack of licenses for [EDIT] $149 USD or such. Not
sure how well the DOS support still works, but I think it claims to
have semi-recent Firefox, OpenOffice, Java, etc. Though I would be
skeptical that it wouldn't boot properly, honestly, but hopefully
they've fixed most of that in their [EDIT] 2.1 release.

>> A hypervisor that can run dosbox and make modern hardware work
>> with old dos programs anyone?  How about dosbox running on a Pentium 133
>> or a Pentium 166 machine with 16 megs of ram?
> Insufficient demand to justify the effort.

Not enough developers. Too many differing machines. Besides,
hypervisors usually require VT-X these days (which means "select" cpus
after 2006). Probably "easier" (so to speak!) to just fix VBox or QEMU
(or KVM) instead. (Too many competing technologies, things change too
fast, not enough stability, blah ....)

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