"PC-98" is a term used by the Western community to refer to the first 5 games of the Touhou Project. "PC-98" is named after the NEC PC-9801 computers on which they ran on. The Japanese community's equivalent is "old works" (旧作 kyuusaku), a term reflecting the technologically inferior FM Synthesis music & 16-bit colour graphics. ZUN has used both the Japanese and English terms interchangeably. PC-98 games are distinguished from later "Windows games" for having been distributed by Amusement Makers instead of Team Shanghai Alice, as well as possessing canon that is ambiguously split from later Windows canon.
Factors which caused the end of the PC-98 games include a hiatus brought on by ZUN's graduation & employment, as well as the decline of PC-9801s. The PC-98 games are less well known, possibly due the ageing hardware they ran on, their release during the dawn of the Touhou community & their relatively limited circulation. Only 200 to 300 copies of Lotus Land Story were sold on its release, while Phantasmagoria of Dim.Dream sold fewer than 100. On 19 September 2002, ZUN ceased sales and support for PC-98 games. ZUN later released arrangements of many themes from the PC-98 games in MIDI format on his old website. ZUN has stated in Akyu's Untouched Score vol.3 that he loves FM music and would continue to create FM music in the modern world.
- 東方靈異伝 ～ Highly Responsive to Prayers (Amusement Makers/ZUN Soft 1996)
- 東方封魔録 ～ Story of Eastern Wonderland (Amusement Makers/ZUN Soft 1997)
- 東方夢時空 ～ Phantasmagoria of Dim.Dream (Amusement Makers/ZUN Soft 1997)
- 東方幻想郷 ～ Lotus Land Story (Amusement Makers/ZUN Soft 1998)
- 東方怪綺談 ～ Mystic Square (Amusement Makers/ZUN Soft 1998)
Unlike the Windows era, descriptions of the PC-98 world were far more vague. Sources suggested the games were set in "an Eastern Country" (not Gensokyo), with statements from Highly Responsive to Prayers and Mystic Square respectively describing the world as "Strange" & "Human [inhabited]". Locations in the Eastern Country included Makai, the Human Village, the Fantasy World, Mugenkan, Reimaden as well as the recurring Hakurei Shrine. The world was inhabited by humans, youkai & demons. Similar to the Windows world, a shrine maiden named Reimu Hakurei (博麗靈夢) lives at the shrine, with her friend Marisa Kirisame visiting occasionally. In PC-98 only, Reimu's turtle Genji also lives at the shrine, along with Mima who haunts and torments visitors out of boredom. Like the Windows games, the PC-98 games begin with Reimu or another character going out to investigate & resolve incidents. However, there was no mention or use of the spell card rules in the PC-98 universe.
The story of the Touhou Project drastically changed with the advent of the Windows era. While the series kept the name "Touhou Project", ZUN stated that it was a "clean sweep", with the current setting of the Touhou Project coming together for the first time in Embodiment of Scarlet Devil. Hence, no PC-98 character has reappeared in a Windows game except for Reimu Hakurei, Marisa Kirisame, Alice Margatroid and Yuuka Kazami. There's been no information about Mima in the Windows era, but ZUN has mentioned in at least 2 interviews that Genjii is "probably still living in the lake behind the shrine".
As ZUN has previously referred to the world of PC-98 as a "study project" which could be ignored in light of the later contradictions of the Windows era, it is sensible to consider the PC-98 and Windows canons as separate. While the Windows games are set in a time period which appears to be later & continuous with the events of PC-98, it is more accurate to consider them as alternate universes which coincidentally occupy adjacent time periods. The Windows universe is a reimagining & reboot of the PC-98 universe, with no actual connection in time or space. Despite the songs, names, roles, personalities & relationships copied to the Windows universe, similarities to the Windows era should be considered as tributes towards PC-98. Some characters (i.e Reimu & Marisa) may resemble their original counterparts closely, while others may only share a few superficial traits & harbour stark differences. This lack of consistency means Windows backstories theorized from PC-98 sources can only be considered as conjecture at best. For example, it is an open possibility that Alice never visited Makai in the Windows universe, despite the reintroduction of Makai in Undefined Fantastic Object.
The NEC PC-9801s were a series of personal computers developed by NEC, which were equipped with 16 or 32-bit Intel x86 CPUs. While outwardly similar to IBM's PC and compatibles, including the use of DOS, it was for the most part a proprietary architecture. PC-9801s included dual µPD7220 video display processors, one each for text and graphics. In graphics mode, they could display sprites with four 16-color palettes selected from 4026 possible colors. Various expansion cards could be installed in PC-98 systems, including more capable video or audio cards, but only the base hardware is required for the Touhou games. ZUN developed the PC-98 games with the PC-9821 computer as a hardware benchmark and specified a 486 at 66MHz as the bare minimum.
As for sound hardware, the PC-9801VX and many subsequent models came default with the PC-9801-26k soundcard. This includes the Yamaha YM2203 OPN FM synthesizer, providing three 4-operator FM synthesis channels plus the three channels of the integrated YM2149 SSG unit. Users could replace this with the PC-9801-86 soundcard with the much more capable YM2608 OPNA chip, doubling the amount of FM channels and adding a few other features. As such, the PC-98 games included two versions of their in-game music, made for either the three or six FM channel hardware. All of the music was programmed in MML with M. Kajihara's Professional Music Driver (PMD), except for Highly Responsive to Prayers which used Mdrv2 for the music driver. Story of Eastern Wonderland also supports outputting to a MIDI device.
- It has been shown in an interview that ZUN still owns a PC-98 computer, on which he played Highly Responsive to Prayers for the first time in years. He felt nostalgic.
- Since any software made for Windows 2000 or earlier can be run both on the IBM-compatible Windows 2000 and the PC-98 Windows 2000 without compatibility problems, technically all Touhou games up to at least Undefined Fantastic Object should be able to run on a PC-98 as long as the appropriate DirectX version is installed. However, since the last PC-98 system was released in 2000 (the PC-9821Ra43, which had a 433MHz Celeron, whereas the system requirements of the Embodiment of Scarlet Devil ask for a 500MHz Pentium) this is generally not viable in practice.
- Sakuya Izayoi may be an reimagining of Yumeko
- Byakuren Hijiri may be an reimagining of Shinki, as both are powerful spellcasters who maintain peaceful relationships with humans and youkai. They are both connected to Makai and even share similar spell cards
- PC-98 characters are often shown in fanworks with Windows characters as though the two canons are connected.
- Because PC-98 computers are no longer sold/manufactured, fans use an emulator to play these games on modern PCs. The emulators most commonly used for the PC-98 games are Anex86, T98-Next, and Neko Project 21 (for the latter it's advised to use the unofficial fmgen builds that're linked from here instead).
- Many fans consider the PC-98 ecosystem to be old or obsolete, to the extent that it is generally associated with nostalgia.
- There are FM Synthesis remixes exist of later songs mimic the PC-98 style. One notable example is the album PC-98 Perfect Cherry Blossom. There's also artwork of modern Touhou characters drawn in the PC-98 style.