231 votes
Accepted

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 ...
33 votes
Accepted

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, ...
  • 98.2k
29 votes
Accepted

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 ...
  • 98.2k
20 votes
Accepted

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 ...
  • 98.2k
19 votes
Accepted

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 ...
17 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 ...
  • 28.6k
15 votes
Accepted

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 ...
15 votes
Accepted

What are the common sources of incompatibility on different MSX computers?

Seemingly there is an entire page dedicated to this (by the MSX wiki). Most of the time, programmers programmed code like how they usually did with the Commodore 64 and ZX-Spectrum and completely ...
  • 2,434
15 votes
Accepted

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 ...
  • 98.2k
14 votes
Accepted

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 ...
13 votes

What are the common sources of incompatibility on different MSX computers?

The famous poke -1,x depends on each computer's slot configuration. The general formula is poke -1,((peek(-1)xor&hff)and&hf0)*1.0625. This is copying the high nibble of the secondary slot ...
  • 1,045
13 votes
Accepted

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 ...
  • 3,842
13 votes
Accepted

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 ...
  • 177k
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" ...
  • 5,667
11 votes
Accepted

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 ...
  • 32.6k
10 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 ...
  • 177k
10 votes
Accepted

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 ...
  • 177k
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!", ...
9 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 ...
  • 57.6k
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 ...
  • 14.1k
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 ...
  • 7,719
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 ...
  • 177k
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 ...
  • 98.2k
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 ...
  • 57.6k
7 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 ...
  • 10.4k
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 ...
6 votes

Pair Am386 with i387

I confirmed this worked as expected, using Am386/DX-40 + Intel 387 co-processor. The trick with the Am386 is having separate clock for CPU/co-processor, as the former runs at 40 MHz and the latter at ...
  • 161
6 votes
Accepted

"Restoring" a 1986 Compaq Portable II (Cabling question)

As can be seen in this video, the hard drive and floppy drive should have separate cables connecting them to the multi-I/O card. To connect your floppy emulator, you need a 34-wire cable with the ...
  • 98.2k
6 votes
Accepted

How did games written for tape-based BBC micro, get officially and unofficially ported to disk, bearing in mind extra workspace needed by DFS ROM?

Both the DFS and the ADFS did indeed reserve memory for themselves at startup, increasing PAGE; this memory was used to hold the current catalogue and other bookkeeping. For adapting existing tape ...
  • 32.6k

Only top scored, non community-wiki answers of a minimum length are eligible