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281 votes
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Why does trying to break into the NT 3.1 kernel reboot my 486DX4 machine?

Short explation The Windows NT 3.1 kernel is incompatible with enhanced 486 processors. Specifically, it is incompatible with 486 processors providing the CPUID instructions. Kernel debugging works ...
Michael Karcher's user avatar
41 votes
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In what ways was the Windows NT POSIX implementation unsuited to real use?

In what specific ways was the POSIX implementation unsuited to real use? It wasn’t unsuited, but it’s important to understand what was certified. In order to meet requirements for certain US ...
Stephen Kitt's user avatar
39 votes
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Was OS/2 a viable alternative for daily DOS and Windows tasks?

The short answer is yes, starting with version 2.0 and even more so with Warp, OS/2 was a viable alternative for daily DOS and Windows tasks, up to and including Windows 3.x. Starting with OS/2 2.0, ...
Stephen Kitt's user avatar
31 votes
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Are later 68000 variants backward compatible with earlier ones?

There are a few incompatible changes, but after the 68010, most of them are surmountable (with a performance penalty) or would only affect operating systems, not applications (at least, not ...
Stephen Kitt's user avatar
29 votes
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Why is the RM Nimbus PC-186 not IBM PC compatible?

While the NM-186 was based on a standard x86-compatible 80186, its architecture was very different compared to the IBM PC’s. The major differences are the firmware, which isn’t PC BIOS-compatible, and ...
Stephen Kitt's user avatar
22 votes
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Why did the PlayStation 2 implement backward compatibility that way?

Probably because it was the only way to get 100% compatibility with the old software library, which was required while most PS2 titles weren't developed yet. No one wants to buy a machine without ...
Jean-François Fabre's user avatar
20 votes
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Do all VGA cards implicitly support CGA and EGA?

All VGAs support the “official” CGA and EGA modes, so most CGA and EGA games work fine. However, compatibility can only be relied upon at the BIOS level; a VGA can be implemented without strict ...
Stephen Kitt's user avatar
19 votes

In what ways was the Windows NT POSIX implementation unsuited to real use?

You would be interested in this video, in which the vlogger installs the POSIX subsystem for Windows NT 4.0sp6 (after previously having tested the version for NT 3.1). It’s a summary of a livestream ...
Davislor's user avatar
  • 8,845
18 votes

Are later 68000 variants backward compatible with earlier ones?

The 68k family is largely compatible between all the members. "Normal" application code can be written to easily run on all the members, unchanged. There are, however, a number of subtle differences ...
tofro's user avatar
  • 35.5k
16 votes

Why is the RM Nimbus PC-186 not IBM PC compatible?

This question is a bit hard, as 'IBM-Compatibility' isn't as clearly defined as advertisement wants to make us believe. In fact, almost any IBM machine could be classified as not compatible, starting ...
Raffzahn's user avatar
  • 227k
16 votes
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How POSIX-compliant is Xenix?

In short: not very. Older versions of Xenix are based on V7 or System III (which are very similar to each other). They had the bourne shell, and large parts of the standard library were already ...
Rico Pajarola's user avatar
15 votes
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Pair Am386 with i387

The Intel 387 should work fine with an AMD 386DX; the latter was a direct clone of the Intel 386. The extra rows of pins are perfectly normal — see this photo for an example. (The extra pins were used ...
Stephen Kitt's user avatar
15 votes
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Why does MS-DOS 5.0 EDIT hang on my XT-class machine with a German 102-key keyboard?

Analysis of the problem The cause is an incompatibility with many pieces in it. It is centered around what the bit 4 of 40:96 in the BIOS data area actually means. This bit is documented to mean that ...
Michael Karcher's user avatar
14 votes
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How compatible is the Leningrad clone with the "original" ZX Spectrum?

Leningrad is a primitive and not particularly compatible clone. However, it is pragmatic, so the incompatibilities are not always going to show up. The main differences are due to a completely ...
introspec's user avatar
  • 4,172
13 votes
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What was the second most common incompatibility in MS-DOS machines?

But was there anything other than video that was a source of hardware compatibility issues in the first wave? Or put another way: after video, what was the second most common source of compatibility ...
Raffzahn's user avatar
  • 227k
11 votes

How compatible is the Leningrad clone with the "original" ZX Spectrum?

In the USSR, the analog TV sets used SECAM, not PAL, so I imagine that the timings will be different between the UK Spectrums and the Leningrad. SECAM is, like PAL just the colour encoding and on top ...
Raffzahn's user avatar
  • 227k
11 votes

Was OS/2 a viable alternative for daily DOS and Windows tasks?

I recently installed OS/2 Warp on a vintage (late-90s) IBM PC 350 with a 200 MHz Pentium MMX CPU and 96MB of RAM. I found that OS/2 Warp works very well for running virtually any DOS or Windows 3.x ...
Brian H's user avatar
  • 60.9k
11 votes

What was the second most common incompatibility in MS-DOS machines?

Aspects I recall, perhaps influenced by the area I was working in at the time: Video display (as you mention) Serial ports Timer interrupt I only had to work with "near-compatible" ...
Greg Hewgill's user avatar
  • 7,009
11 votes
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Lotus 1-2-3 and Microsoft Flight Simulator as unofficial compatibility benchmark?

Yes, I think you did. E.g. from The Digital Antiquarian: Having quickly concluded that simply copying IBM’s ROMs wasn’t a wise option, Compaq hired a staff of fifteen programmers who would dedicate ...
Tommy's user avatar
  • 37.5k
10 votes
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Can 6502 programs be transliterated to the SPC700?

The SPC700's instruction set is derived from the 6502's, but moves the instructions around and adds a few. But is it fully backwards compatible? No. At least not fully. The instruction set is mostly ...
Raffzahn's user avatar
  • 227k
9 votes

Do all VGA cards implicitly support CGA and EGA?

The other answers are good, but one specific area where VGA cards are generally incompatible with CGA is with respect to CGA's Composite mode. In the video "CGA Graphics - Not as bad as you thought!", ...
Robert Columbia's user avatar
8 votes

Are later 68000 variants backward compatible with earlier ones?

But is there any incompatibilities which could keep code written for the 68000 from being run the same way on a later model? Yes. Any 68000 program that used the "move from SR" instruction in user ...
JeremyP's user avatar
  • 11.8k
8 votes

Why is the RM Nimbus PC-186 not IBM PC compatible?

The 80186 contains a CPU and several peripheral units, including a two-channel DMA Controller, a Programmable Interrupt Controller and three 16-bit timers. The IBM PC-AT and PC-XT also have a DMAC, ...
TonyM's user avatar
  • 4,486
8 votes

USB ports for a 486 laptop (pccard 16bits)

The laptop you describe is unlikely to be able to support USB ports, for hardware reasons. But there may be an alternative solution. The first USB standard (version 1.0) was published in 1996, but ...
Kaz's user avatar
  • 8,176
8 votes

Are later 68000 variants backward compatible with earlier ones?

In addition to the other excellent answers, sometimes the addition of caches could cause incompatibility. The 68010 had a single instruction cache that couldn't really cause any problems. The 020 ...
user's user avatar
  • 15.3k
7 votes
Accepted

What changes made some Atari ST software incompatible with the Atari TT?

Beyond the usual TOS compatibility issues which affected all Atari STs, the TT add the following twists: its faster CPU meant that some programs (games) ran too fast; this wasn’t as much of a problem ...
Stephen Kitt's user avatar
7 votes

What changes made some Atari ST software incompatible with the Atari TT?

The question is sort of broad, since there are many ways to write software that targets the specifics of ST hardware, and which leads to programmer assumptions that break when the hardware changes ...
Brian H's user avatar
  • 60.9k
7 votes

Pair Am386 with i387

AMD 80386 chips are die-identical to Intel's, as AMD cloned the Intel 386. So, putting an Intel 80387 (or ULSI 80387 or IIT-387) will do fine, as long as their speed is equal or faster than the main ...
mcleod_ideafix's user avatar
7 votes

Did the Harris 80C286 differ from Intel's 80286 in its behaviour?

Does the Harris 80C286 have any difference in behaviour from an Intel 80286 as far as the programmer is concerned? The Harris/Intersil/Renesas 80C286 is, like its 80C86 predecessor fully compatible ...
Raffzahn's user avatar
  • 227k
7 votes

In what ways was the Windows NT POSIX implementation unsuited to real use?

Having tried to use it, I found it had a major fault that rendered it unusable. Delete file while in use did not function; and quite a few applications from the era expected this to work; with them ...
Joshua's user avatar
  • 1,858

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