Please keep in mind that *existing software* is also a metric in my consideration.
What *existing software* do you want to run? If it's pre-compiled MSDOS applications then you will need to reproduce an entire IBM PC, either at the hardware level or using a custom BIOS to interface to your non-standard hardware (with reduced compatibility). If you are happy to recompile source code then you have more flexibility, but then the CPU choice also becomes less of an issue.
If I built a retro computer using 8088 I can build it in the style of an IBM PC XT compatible with some AT features, complete with a compatible BIOS. This will allow vanilla MS-DOS as well as a good selection of existing DOS programs to work, including games.
I think you may be underestimating the amount of work required to produce a sufficiently XT compatible machine, particularly for games.
My first PC was an
actual IBM, but it was not compatible with a lot of PC software because it was an
IBM JX. For me it was an excellent choice because I had the technical reference manuals and a desire to learn the PC architecture inside and out. The incompatibilities taught me a lot because I had find out why they occurred and fix them - including hacking into games, writing drivers and making my own hardware. However if you
don't want to do that it could be a nightmare.
The 8088 seems attractive due to its low pin count and compatibility with Intel peripherals, but needs a lot of specific support hardware to become a fully functional XT. And in the end all you have is another crappy XT clone. What's the fun in that?
An interesting bit of history -
Why the IBM PC Used an Intel 8088"For IBM it was extremely different because this was a project where they let a supplier -- a partner, whatever you call us -- shape the definition of the machine and provide fundamental elements of the machine. When they first came to us, their concept was to do an 8-bit computer. And the project was more notable because they were going to do it so quickly and use an outside company....The novel thing was: could you work with outsiders, which in this case was mostly ourselves but also Intel, and do it quickly? And the key engineer on the project, Lou Eggebrecht, was fast-moving. Once we convinced IBM to go 16-bit (and
we looked at 68000 which unfortunately wasn't debugged at the time so decided to go 8086), he cranked out that motherboard in about 40 days." - Bill Gates.
Basically, IBM decided to use the 8088 because it was
cheap, and they just wanted something to compete with other 8 bitters. If they had picked the much more powerful 68000 they might still have a hold on the PC market today. As it was they realized their mistake (and tried to correct it with the PS/2 line) too late.
I am not familiar with the 68000-based systems (they are virtually nonexistent in China) so is there any open standards comparable to IBM PC?
Compared to the PC not as much, but if you want to run existing PC software (including games) you need full PC compatibility anyway so any
other standards are irrelevant.
OTOH why limit yourself to recreating a boring PC? Be adventurous, learn new stuff, try doing something everybody else
hasn't done before!
I am not that keen on coding everything in assembler, so availability of some kind of ISO C compiler is almost a must, and the ability to write startup code in as little assembler as possible is a bonus point.
Few of us code everything in assembler (I am one of the exceptions) but 68000 machine code is
much easier to work with than 8086. Orthogonal instruction set, no segment registers, few instructions to learn, powerful easy to remember opcodes and neat looking code. Compared to Intel it's a dream. Why don't you try it?
My software work platform is Linux and macOS so Windows-only tools are out of consideration.
MacOS was originally 68000, and Linux is based on Unix which the 68k instruction set is particularly well suited to. It may be more familiar than you think...
Motorola 68000"the 68000 became the dominant CPU for Unix-based workstations including Sun workstations and Apollo/Domain workstations, and also was used for mass-market computers such as the Apple Lisa, Macintosh, Amiga, and Atari ST. The 68000 was used in Microsoft Xenix systems, as well as an early NetWare Unix-based Server."
Notable systemsThe original Apple Macintosh and early successors use the 68000 processor as their CPU.
The original Apollo Computer workstations, DN100, DN400 and DN600 use two 68000 processors as main CPU.
The 1981 SUN workstation and its subsequent commercial spinoff the 1982 Sun-1 workstation used the 68000 as their CPU.
The Sega Genesis game console uses a 68000 processor (clocked at 7.67 MHz, 15/7 of the NTSC video colorburst frequency) as its main CPU and the Sega CD attachment for it uses another 68000 (clocked at 12.5 MHz).
SNK's Neo Geo.
The Commodore Amiga 1000, 2000, 500, 600 and CDTV use the 68000 processor as their CPU.[24]
The Atari ST computers use the 68000 processor, initially with a clock speed of 8 MHz, and later switchable to 16 MHz in the Mega STe.
CDTV, the world's first compact disc based multimedia platform, uses the 68000 processor as its CPU.[25]
The TI-89 Graphing Calculator uses the 68000 processor at 10, 12, or 16 MHz, depending on the calculator's hardware version.
The CP System uses the 68000 processor at 10 MHz;