In 80's - 90's Japan, a number of unique PC architectures were released because they needed to handle Japanese language. Most of them are incompatible with IBM-PC nor Apple II. I roughly introduces some Japanese PCs and gaming consoles to which Ultima games were ported.
NEC (Nihon Denki)
NEC was the largest PC manufacturer. They formerly dominated Japanese PC market by until Windows 95 was released. NEC had released a number of PC models belonging several architectures, from 8-bit handheld PC-2001 to PC-100, one of the firstest GUI-based PC released at 1983.
PC-8801 having Zilog Z80 CPU was introduced at December 1981. The original PC-8801 is not so suitable for gaming because of lack of synthesizer audio, however, PC-8801mkIISR, an enhanced model released at January 1985. PC-8801mkIISR has built-in FDDs, Yamaha YM2203 audio, ALU graphic acceleration controller and an ATARI-style joystick port, so that PC-8801 became suitable for gaming.
PC-8801mkIISR and successor models were primary target for gaming along with MSX, especially in 1987 - 1989, until PC-9801VM took over this position.
Starcraft Ultima II and III and Ponycanyon Ultima I - IV were released for the architecture.
PC-88VA is a 16-bit(NEC's V30 enhanced 8086 CPU) computer architecture that has good compatibility with PC-8801mkIISR(like Apple II GS against Apple II). PC-88VA, introduced at March 1987, has higher video modes such as 640x400, 256 colors and sprite function. PC-88VA did not achieve good sales against the rivals such as X68000, and ceased at around 1989.
Ponycanyon Ultima I - V were released for the architecture.
PC-9801, the first model was introduced at February 1982, is 8086-based architecture but incompatible with IBM-PC. PC-9801s were wide-spread on Japanese business PC market, and CPU-and-video-enhanced model, PC-9801VM(V30-10MHz and 640x400, 16 of 4096 colors video) was introduced at July 1985.
PC-9801VM, UV(3.5'' FDD model released at May 1986) and their successors, with optional PC-9801-26K Yamaha YM2203 audio card, became good gaming platform and dominated late-80's to early-90's PC gaming market, replacing PC-8801mkIISR. At October 1992, PC-9821 architecture was introduced. PC-9821 has good compatibility with PC-9801VM and enhanced video(640x480, 256 of 16k colors) and audio (Yamaha YM2608).
Starcraft Ultima II and III, Ponycanyon Ultima I - VI and the Savage Empire, and Ultima Underworld I and II and Ultima VIII were released for the architecture. Ultima VI, the Savage Empire and Underworld I/II require VM-based architecture(some of them requires 386 or faster CPU) and Ultima VIII is for PC-9821 computers.
MSX was a Z80 based platfom, and several manufacturers such as Panasonic and Sony had released MSX computers. MSX computers had basically lower price than other Japanese 8-bit computers, so that achieved good sales in this country.
Ponycanyon Ultima I - IV(including Ultima III ROM cartridge edition) were released MSX2 architecture.
Fujitsu was yet another rival, along with Sharp, in 80's - '90s home computing market against NEC.
FM-7, or Fujitsu Micro 7, introduced October 1982, is Motorola MC6809 based architecture. The original FM-7 was low price, but good video performance with second 6809 as graphic controller(unless the programs require complex graphic processes). FM-7 architecture has several variant models; FM-new7(identically same as original FM-7 and having lower price), FM-77(having slightly faster video and built-in 3.5'' FDD) and FM77AV series(having enhanced video of 4096 colors/320x200pix).
Starcraft Ultima II and III, and Ultima IV were released for the architecture.
FM TOWNS, introduced at February 1989(initially proposed at Fall 1988 but delayed by illness of Emperor Hirohito), is an intel i386 based architecture. FM TOWNS can overlay High-res-but-low-color(640x480, 16 of 4096 colors) screen on High-color-but-low-res(320x240, 32768 colors) screen, the function being suitable for porting VGA or Amiga games to the architecture. That is, Japanese characters that require High-res screen are placed on overlaid screen.
Ultima trilogy, IV - VI, and Underworld I/II were released for the architecture.
In Japan, PC compatibles were not considered as gaming devices, before DOS/V had been released. DOS/V is a DOS that enables standard 286/VGA PCs to handle/display Japanese text.
Several PC-based architectures such as Toshiba J-3100(based on T-3100 laptops), IBM PS/55(based on MCA PS/2) and AX architecture(PC/AT with JEGA video card and AX keyboard) were released before DOS/V, but they were primarily used in offices.
DOS/V became popular in Japan at leased after Windows 3.1 was released. The term "DOS/V" is sometimes used as PC compatible in Japan, even if DOS/V OS cannot be installed thereto.
Ultima VIII was released for the architecture.
Several Ultima games were released for Nintendo Family Computer(Famicom, Japanese counterpart for Nintendo Entertainment System in United States), Game Boy and Super Famicom(Super NES in Japan), and Sony Playstation.