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I'd like to share a little project I've been working on.

I was getting annoyed at overhauling my emulator setup every time I wanted to play a new game, so I decided to split things up. The result is my "cat pack" - four separate emulator setups based on the latest unofficial Neko Project II build.

I have designed the setups around four real-life PC-9801/9821 models, tweaking settings for maximum performance and compatibility. The setups are complementary - for each setup there is at least one game that runs poorly or not at all on the other three setups.

PC-9801VM (1985)
Compatible games:
- Ys series (Nihon Falcom)
- 1920 Series: Kohakuiro no Yuigon (Riverhill Soft)
- Onryou Senki (Studio Wing)
- Puzznic (Broderbund Japan)

PC-9801RX (1988)
Compatible games:
- Roli Roli Rolling (Bio 100%)
- Hell Ogre (ZIGO Watt)
- Dennou Gakuen - Cybernetic Hi-School (Gainax)
- Okhotsk ni Kiyu (Login Soft)

PC-9821As (1993)
Compatible games:
- Steam Hearts (Giga)
- Farland series (TGL)
- True Love (Software House Parsley)
- Corpse Party (Kedwin/Kenix)
- Eve: Burst Error (C's Ware)
- Policenauts (Konami)

PC-9821Xs (1994)
Compatible games:
- Touhou Project series (ZUN Soft)
- Night Slave (Melody)
- Briganty (Giga)
- Queen of Duellist series (Agumix)

It would be impossible to create an individual setup for every possible configuration, but I think these four cover most of the major compatibility issues (CPU architecture, BIOS settings, sound boards, GDC/Graphic Charger chips, etc.)

Please tell me what you think.

Detailed emulator settings:

***Note: These are emulator settings, not the exact specs of the reference hardware.***

PC-9801VM (1985)
CPU: V30 (u70116) 8 MHz (1.9968 MHz x 4 = 7.9872 MHz)
Architecture: PC-9801VM
RAM: 640 KB
Graphic Display Controller: uPD7220
Graphic Charger: GRCG
Sound board: PC-9801-26K, Jast Sound PCM device
BIOS: NEC N-88 BASIC(86) version 1.0
Dip Switches:
SW2-5 ON: Retain memory switches
SW2-6 ON: Disable hard disk
SW3-8 OFF: CPU mode Low
Memory Switches:
Use math coprocessor, 8 MHz
Use sound board

PC-9801RX (1988)
CPU: 286 12 MHz (2.4576 MHz x 5 = 12.2880 MHz)
Architecture: PC-9801VX
RAM: 640 KB + 1024 KB (1.6 MB)
Graphic Display Controller: uPD7220
Graphic Charger: EGC
Sound board: PC-9801-26K
BIOS: NEC N-88 BASIC(86) version 2.0
Dip Switches:
SW2-5 ON: Retain memory switches
Memory Switches:
Use math coprocessor, 8 MHz
Use sound board

PC-9821As (1993)
CPU: 486 33 MHz (2.4576 MHz x 14 = 34.4064 MHz)
Architecture: PC-9801VX
RAM: 640 KB + 7168 KB (7.6 MB)
Graphic Display Controller: uPD7220
Graphic Charger: GRCG+
Sound board: PC-9801-86, MIDI (GS)
BIOS: NEC N-88 BASIC(86) version 2.0
Dip Switches:
SW3-5 ON: Fast DMA clock

PC-9821Xs (1994)
CPU: 486 66 MHz (2.4576 MHz x 27 = 66.3552 MHz)
Architecture: PC-9801VX
RAM: 640 KB + 7168 KB (7.6 MB)
Graphic Display Controller: uPD72020
Graphic Charger: GRCG+
Sound board: PC-9801-86, MIDI (GS)
BIOS: NEC N-88 BASIC(86) version 2.0
Dip Switches:
SW3-5 ON: Fast DMA clock

Common settings:
Sound sampling rate: 44 KHz
Sound buffer: 100 ms
Screen: Window(soft), Vsync disabled, Full frame
Screen option: no skipline revisions, PC-9801-24 16-color board enabled
Screen timing: T-RAM 1, V-RAM 6, GRCG 8, Real palettes adjust 0
Sound option - Joypad enabled
Dip Switches:
SW2-8 OFF: GDC clock 2.5 MHz
SW3-4 ON: Do not control floppy motor
ini file settings:
ITF_WORK=TRUE enable ITF emulation
STATSAVE=TRUE enable save states
I286SAVE=TRUE enable debugger

This is a brilliant idea

Thank you for sharing

Excellent idea. Thanks for sharing!

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Excellent work as usual kobushi

Is there actually a dipswitch which allows to switch between 15 and 31 Khz modes? I think I read that once somewhere, but I might misremember it.

The regular horizontal frequency for the PC-9801 is 24.83 KHz. Late models started using 31.47 KHz (i.e., VGA frequency) by default, but you could switch back to 24.83 by holding Grph+1 at bootup. (Grph+2 reverts to 31.47). There never was a dip switch.

The switch in horizontal frequency was done merely to accommodate newer monitors, and is meaningless in an emulator.

Wait, but there was still 15 Khz output for 640x200, no? I thought that was why Neko had scanline emulation in the first place.

I'm pretty sure the PC-9801 stays at 24 KHz, even in 640x200 mode. (unlike the PC-8801)

Launch a game with scanlines such as Ys, and check Neko's emulator status information (Other->About->More). On the fourth line, under GDC, you'll see that the horizontal frequency is still 24 KHz.

The monitor I use with my real PC98 machines is an LCD from 2007 that supports 24 KHz. I'm sure it doesn't support 15 KHz, but I have no problem running older games with scanlines. I don't think even original PC-9801 monitors supported 15 KHz as a general rule, because there were special 2-mode (15/24 KHz) and 3-mode (15/24/31 KHz) "multi-sync" monitors sold separately. (In case you've ever wondered where the name for NEC's MultiSync brand of monitors comes from, this is it).

That's probably because Neko runs all games (even the 640x200 ones) at 24 kHz -- the scanline feature is just an optional software emulation which you can gradually set from full black to full transparency on the fly, and the interlaced games don't suddenly change frequency when applying/disabling scanlines in Neko.

The original help file further indicates that the software scanlines are meant to reproduce the look of interlaced games on 15 kHz capable monitors, which I assume must have been a mode somehow familiar to PC-98 users.

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ITO Takayuki's page mentions 15 KHz in 640x200, but I'm not sure what to make of this. Specifically, this paragraph:
●PC-98専用モニター
PC-98シリーズの標準的な解像度は、水平同期周波数24KHzで出力されます。
したがって、PC-98用のモニターは使えないと思ってください。
PC-98GS用などのごくごく一部が15KHzに対応しますが、わからないモニターはまず使えないと考えましょう。

I think Takayuki Ito is wrong on this particular point (no offense to the good man )

The page you link to seems to confirm my thoughts - it's talking about connecting various game consoles to a computer monitor (most older consoles like the SNES/SFC and the Genesis/Megadrive run at 15 kHz).

The pages says that PC-98 monitors are generally unusable because they only run at 24 kHz. Besides a few exceptions, PC-98 monitors don't support 15 kHz. The exceptions are the multisync monitors and the models that included TV tuner/video capture features.

Kaminari,
I think Yui was making a comparison to the PC-8801 when he wrote the Neko help file, because there is no "15 kHz" mode that I can find.

Also, Neko doesn't force 24 kHz - it is possible to run at 31 kHz using a software tool such as TT21. People used to do this because it made the screen less jittery on old CRTs. You can confirm that Neko is running at 31 kHz by checking Other->About->More, or by just running some DOS software (the screen gets messed up). You could program a similar tool to force 15 kHz, but I don't think games would display properly.

I hope you don't mind: the link is dead so I put a copy up at:

http://www.retroprograms.com/PC98/PC98_Utils.html