29 Jan
1998
29 Jan
'98
1:50 a.m.
In a message dated 98-01-29 08:44:40 EST, you write:
<< > I looked in my never used copy of os2 version 1.3 standard edition and
found
no mention of rexx so maybe it arrived in version 2.x
but i'm not opening
my
shrinkwrapped version to find out! minimum
requirements for 1.3 are a 286,
2meg, and 12 meg of hdd space.
: Worth a try then. But am I right in thinking that the AT doesn't
: implement all the 286 modes properly? I'm sure the XT286 doesn't. >>
...an AT doesnt implement 286 models properly? i dont get it. AT=80286. now,
all 286 machines had a limitation about being able to switch from protected
mode to real mode and back to protected mode without major work and/or a
reboot. the 386 does this all smoothly under software control. it's also my
understanding the XT286 is just a regular old 5170 board in a 5160 case.
david
29 Jan
29 Jan
3:19 a.m.
SUPER's right, I do believe. The 286 could switch INTO protected mode,
but not out, as I recall. And, there were no virtual '86 modes, as the
386 has in protected mode. Along with a 16MB address space limit
against 4GB for 386.
But these are just the limitations as to why the 286 can't do 386 code.
I don't think theres any reason why the AT couldn't run 286 protected
mode programs as it was the standard around which those codes were
written.
The XT286 seems to bring to mind wome compatibility issues, but I can't
remember what they were. Unless the XT286 was build around 86 support
chips and bios (just to tap 10 or 12mhz speed for XT programs) in which
case you might have some problems.
I guess....
-Mike
SUPRDAVE wrote:
In a message dated 98-01-29 08:44:40 EST, you write:
<< > I looked in my never used copy of os2 version 1.3 standard edition and
found
no mention of rexx so maybe it arrived in version
2.x but i'm not opening
my
shrinkwrapped version to find out! minimum
requirements for 1.3 are a 286,
2meg, and 12 meg of hdd space.
: Worth a try then. But am I right in thinking that the AT doesn't
: implement all the 286 modes properly? I'm sure the XT286 doesn't. >>
...an AT doesnt implement 286 models properly? i dont get it. AT=80286. now,
all 286 machines had a limitation about being able to switch from protected
mode to real mode and back to protected mode without major work and/or a
reboot. the 386 does this all smoothly under software control. it's also my
understanding the XT286 is just a regular old 5170 board in a 5160 case.
david 
7:35 a.m.
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12:57 p.m.
Tony:
I just seem to remember _something_ about the XT286 that made me avoid
it for true 286 stuff. Maybe it was the memory. Most after market AT
boards had room for a meg or two. Maybe it was the 640...
-Mike
Tony Duell wrote:
I've not got the XT-286 techref to hand, so I
can't look at the
schematics. But I seem to remember that it's _very_ similar to the PC/AT
- it's a lot closer to that machine than to the XT. There are 2 DMA
controllers, 2 interrupt controllers, the 8042 keyboard controller (so it
takes an AT keyboard), etc. My thoughts when I looked at the schematics
were that it was a repackaged AT. Of course they could have missed out
the extra reset logic, but I doubt it.
It does use a non-standard motherboard, though. The memory is a little
odd - 128K in DIPs (4 off 64K*4, 2 off 64K*1 for the parrity) and 2 256K
SIMMs for a total of 640K.
I guess....
-Mike
-tony
9824
days inactive
9824
days old
3 comments
3 participants
participants (3)
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