whaka wrote on 2021-10-10, 13:57:
Jo22 wrote on 2021-10-10, 07:09:
There's a difference, though, I think. 😀 If you added a NEC V20/V30 to any random XT,
it would become very compatible with most DOS software, way up to the end of the 90s.
i don't really get your point here. the fact is few moderns program run on 8088. even if V20 or 30.
I thought thw same, originally. But the more I experimented with an XT and DOS programs, I realized that the NEC series CPUs are slightly higher evolved than the 80186, even.
And In terms of compatibility, both V20/V30 and 8018x are on par with the 80286 processor.
That means, as far as I can tell, that they can run most normal DOS programs - about 90% or so are fine with the 286 instruction set.
They only relevant things both 8018x and the NECs are missing are the MMU and Protected-Mode. So no Windows 3.1 party time, hi.
However, the unpatched Windows 3.0 VGA driver (186 instructions!) will work on a XT if a V20/30 is installed.
Only a few DOS programs that run in Real-Mode use 386+ instructions, also.
The Creative drivers are among ofthem (not surprisingly).
- On a 286 system, 386+ instructions can even be intercepted through NMIs/CPU Exception Faults and emulated. EMU386 does use that, for example.
So long story short, most DOS programs from the 90s require these things:
- 80286 processor (or similar or higher)
- MS-DOS 3.2 or compatible or higher
- 512 or 640KB base memory (installed, not free)
- VGA
VGA.. VGA may seem like a luxury, especially to Amiga users.
However, VGA never was meant as a luxury. It was designed to be cheap right from the start.
And many users replaced their old video boards through VGA cards from. The late 1980s onwards, making VGA a defacto standard that united all the video modes of its predecessors (MDA, CGA, EGA, MCGA) into one device.
Even IBM itself advertised VGA to IBM PC/XT users.
Exceptions.. In some cases, an FPU aka NPU is also required.
That's the case if the application uses floating point.
Programs from the 486 era sometimes need that capability.
On a 286 and later, a NPU can be emulated in software through the same trickery that EMU386 uses.
That's why some DOS Compilers have both a FPU emulator and a floating-point library to choose from.
If the application is linked with the FPU emulator, it can make use of FPU commands - which comes in handy if it is run on a PC with a physical FPU.
However, that doesn't work on a XT, since EM87 etc need the exception handling feature of a 286 or higher CPU.
So in order to use floating-point arithmetics here (no 87 installed), a floating-point runtime must be used which doesn't act like a FPU.
Last but not least, there's the BIOS.
Some later programs may need service routines present in the AT BIOS only.
These won't work on XTs, unless they run on modernized BIOSes.
However, well written programs typically used DOS as some sort of HAL, if it was possible, not BIOS functions. 😀
whaka wrote on 2021-10-10, 13:57:devlopper can set a limit for the kickstart version. the kickstart contain some libraries used by (and are part of) the OS and t […]
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Jo22 wrote on 2021-10-10, 07:09:
The Amiga platform was different, though. Amiga programs didn't use different code paths, or used drivers for different video hardware etc.
In terms of compatibility, Amigas were/are more like Macs, I think. Mac OS applications contain a minimum OS requirement information in their headers.
If the program was written on, say, System 7.5.1, it won't execute on 7.5.0 - even if that OS has all the API functions needed! 😔
devlopper can set a limit for the kickstart version. the kickstart contain some libraries used by (and are part of) the OS and their version sometimes matter.
but from 1985 to nowdays, kickstart/workbench can and has always been uprgadable on all amiga. there's no real "artificial" software limitation.
the only comparison with mac is they used same cpus. but politics and spirit were really different 😀
I did talk about the philosophy, yes.
Amiga programs wriiten in the 90s rarely ran, if at all, on unmodified Amigas from the 1980s.
To make programs run, they had to be upgraded heavily.
Especially those awkward 68040-68060 accelerator boards, not to mention PowerPC processor boards.
I mean, a little RAM upgrade and a simple CPU swap (68000 out, 68010 in) is one thing.
Installing an huge, expensive behemoth of a CPU card something completely different.
It's like installing a parasite on a host.
And the PPC things were the upshot, replacing the whole architecture M68k of an Amiga.
They're as alien as that crazy SuperCPU addon for the C64.
Sure, each to his own. It's a freaky thing for computer freaks. That's fine.
But my point is: That's not what the normal Amiga users have or had.
That's what I meant to say. In order to use hobbyists software from the 90s written by Amiga die-hards (commercial software went extinct), someone needs a Frankenstein Amiga. The ubiquitous Kick 1 - 2/3 EPROM board is the least to be worried about.
Hence, I agreed with user hyoenmadan
that back then, real Amigas were affordable but that now emulation is the way to go.
Emulators can emulate most of these funny upgrades that became a requirement.
Edit: I'm sorry for my English again. Writing on a mobile device is not easy. It will constantly replace the words I type in.
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