► Introduction

NEC PC9800 series computers are very new to me.
I only knew one title, well, its DOS port : Knight of Xentar, or Dragon Knight 3.
Its game library is very huge, full of eroge / hentai games but also with some hidden treasures you have to discover.
Unfortunatly, it's very hard to play them.
First because you have to know japanese, Second because available emulators aren't very user friendly.

► Tech details

So what's the core of PC98 computer ? Not a Z80 like its predecessor, the PC88.
You'll read (too) often that the PC98xx are similar to 286 PC.
Be careful, similar doesn't mean a PC software would run on PC98xx and vice versa.
While the 2 are based on x86, there is a LOT of differences :

Interrupts Comparison
Memory map Map
by Darklanlan [CC0], via Wikimedia Commons
I/O port Details
Hardware Comparison
Load Address per floppy type
registers values

Most of the tools you use for DOS RE could be used, but be careful with IDA : its auto comment feature is PC based, not PC98
And while Ralf Brown interrupt list lists some of the PC98 interrupts, it's incomplete. You'll need to dig on japanese only books to get all of them.

► Video

On text mode, you're able to draw Japanese character.
It prints JIS character (word) to TextVRAM (A000:0000)
If you RE games, you'll find SJIS text .. the SJIS character is converted by code to JIS decreasing MSB by 0x20

► File format

FDI : floppy
D88 : floppy, difficult to make the difference between a PC88 (z80) and PC98(x86)
HDI : hard drive

► Toolkit

► Links

NEC PC98 Basic reference
46 OKUMEN projects
Nana's PC98 Translations
More technical books