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My Continuing Adventures With The NEC PC-9821…


Following on from my introduction to and restoration of the NEC PC-9821, part of the legendary PC-98 series from Japan, I learn a lot more about the machine and how it differs from a PC and start exploring YAHDI - Yet Another Hard Disk Image.


This is my NEC PC-9821 and I made a somewhat popular video all about the history of the PC-98 and 88 platforms and the pretty complicated and in-depth restoration of this machine back in January which I was hoping would lead to a pretty quick and easy series where I’d get Windows 95 back up and running, install various games, and take a look at some of the weird and wonderful hardware inside.

Now, if you saw that at the time and the rather big mistake which caused me to have to edit it and reupload it - which is never ideal - you might have an inkling as to why things have gone a little bit off track. See, I thought this was basically just a bog standard mid-90s IBM compatible PC running Windows with a few extra odd bits thrown in for a bit of backwards compatibility.

Turns out that’s not the case - even in 1996 when this machine was built, the PC-98 was still a very strange beast indeed, and so I’ve had to reevaluate the whole project - and I thought, well, why not bring you along on that journey too?

And before we get into it, I want to give a very big shoutout to a member of the PC-98 community known as thepirategamerboy12 - he’s certainly not the only one who’s helped me out but he really did go above and beyond in holding my hand with all of my silly questions and that started by providing me with a disk image called YAHDI or “Yet Another Hard Disk Image” - so let’s take a look at that.

You see, getting a PC-98 up and running - even a later machine like this one - isn’t just a case of dropping a hard disk or what have you into it, booting from a DOS floppy and formatting the thing. I mean, it doesn’t boot from DOS floppies for a start, in fact it doesn’t even use the same disk format. The original install media is incredibly difficult to come by and of course it’s all in Japanese, so by far the best place to start is with YAHDI.

This is a preconfigured disk image created - from what I can see - back in 2014 by an NFG Games forum user known as kobushi. It includes quite a lot of stuff, including DOS versions 6.2 and 5 - and they’re the proprietary customised versions by NEC of course - a file manager, a graphical menu system, disk imaging tools, audio and CD-ROM drivers which are of course proprietary to the PC-98, image viewers, audio players, utilities, games, and who knows, I’m still exploring it myself and hopefully we can check out everything it has to offer over the next few videos.

So, I got it imaged to a Compact Flash card which was simple enough and booted up the PC-9821 - and then immediately ran into a problem.

YAHDI - let’s call it YAHDI from now on as it’s a bit less of a mouthful - is supposed to run a configuration script on first boot to set up things like sound drivers for the specific machine that you’re running it on. But in my case, I got nothing and it seemed like nothing was working. On a whim I decided to hit the W key as per the instructions and it turns out that the script was running - I just couldn’t see it.

Then it booted into the menu system - known as BM - and all of the options were blank. Now ultimately this turned out to be a setting in the BIOS which my new friend helped me to track down, so let’s take a look at that BIOS because as you might expect, it’s odd.

So at first glance you might think that this is just your fairly typical mid-90s PC BIOS, and you can kind of fumble your way through it by firing up Google Translate on a mobile phone and pointing it at the screen. But the first big thing that sticks out are these virtual DIP switches. If you’ve ever used something like the MAME arcade emulator you’ll probably be familiar with the concept, and these were indeed physical switches on earlier machines but now implemented in software. There is a very important one that we need to change to fix some game compatibility issues, and we’ll have a look at that shortly.

For now, the setting that solves all of our problems is this one - which switches from graphical to text based boot. Now, I’m not really sure of the exact technical details here, but as mentioned in the first video, the PC-98 uses a ROM chip to store text characters thanks to those complex Japanese alphabets, and I’m wondering if this is the setting that initialises that.

Either way, we can now see the options in BM and explore a little bit further.

I must admit, the first time I saw this I thought it was very cool. This is the Filmtn file manager and I’m barely going to scratch the surface of it in this video but it’s certainly something I’m going to learn more about. I mean - look at it!

For now, all we need to know is that we can press R to run various things, and thankfully this is a little bit more familiar in that we’re dealing with DOS things like .EXE and batch files.

So I thought I’d check out some games based on pirategamerboy’s recommendations. I haven’t managed to get all of them running yet but here’s a small flavour of what’s to come.

First up I checked out 4D Driving. It turns out this is actually the official PC-98 port of STUNTS - known as 4D Sports Driving in some markets - which was released on DOS in 1990 and the Amiga in 1992. This dates from a year later and is a massive improvement on the Amiga version in particular in pretty much every way - the music and sounds are better, it runs much smoother and at a rather impressive FPS, and it’s just loads of fun to play. As with most of the games I’ve checked out it certainly has its own unique sound to it as well.

Definitely recommended.

Oh, and I also enjoyed playing with the track editor which reminds me a bit of SimCity. Of course it supports the mouse as well and a few different tilesets with different themes. It’ll even show you this 3Dish render of your custom track. Good stuff.

Speaking of SimCity, the PC-98 also got ports of various other DOS games including the original SimCity and SimCity 2000 which doesn’t seem to like any of the audio hardware in my machine but is otherwise playable, oh, and Lemmings which is - well - basically Lemmings although it sounds pretty cool on the PC-98 hardware.

Lemmings and a few of the other games use a really clever system of self-extracting and mounting virtual floppy images to run. It’s evident that a huge amount of work has gone into YAHDI to get all of this stuff working.

There are also versions of Doom and Wolfenstein 3D on here which I was looking forward to checking out but for whatever reason I haven’t managed to get them running yet. Definitely something to investigate.

Of course, as interesting as it is to look at the differences in games that we all know and love, the appeal of the PC-98 is definitely in some of those more exclusive games - particularly the ones in the folder market NSFW.

Err… Maybe not that one…

So I thought I’d check out Night Slave.

Now, the first time I played this there was something very odd going on with the intro and title screen, and once I got into the game itself that definitely didn’t look right either. Again, my new friend helped me out and pointed me towards the GDC clock speed setting in the BIOS.

The GDC is the PC-98’s Graphics Display Controller - if you cast your mind back to part 1, this was a very sophisticated graphics chip known as the NEC PD7220 dating back to 1981 - so sophisticated in fact that Intel actually licensed it from NEC and released it as the 82720 in the west. It was basically pushing VGA-like graphics years before that was a thing, and is generally considered to be the first dedicated PC GPU.

The good thing is that this later machine actually has one in it in some form or another, but it’s running at the wrong clock speed for some of those earlier games, and it turns out that one of those virtual DIP switches that I mentioned earlier actually controls this clock speed and setting it to 2.5MHz makes our graphical woes a thing of the past.

Now, quite why Night Slave was designed with the older, slower speed in mind I’m not sure as it was a much later release from 1996. If I were to hazard a guess I’d probably say it was for backwards compatibility with much older PC-98 machines.

Still, it’s running great now, so what is Night Slave? Well, on the surface I’d probably compare it to Turrican - it’s basically a massive robot stomping around a barren landscape and blowing stuff up, which is always great fun and I enjoyed it a lot. Apparently the game also incorporates RPG elements like the ability to upgrade your mech, so I’m definitely going to be revisiting this one.

Now, as to why it’s in the NSFW folder - I must admit I didn’t find out myself, but Wikipedia does offer something of a clue.

I’m gonna have to play it some more. It’s a good game!

Another one was Bomber Quest and I wanted to check this one out because pirategamerboy has been doing some translation work on it. It’s another PC-98 exclusive and another slightly later game from 1994. It’s an RPG puzzle-like game that features bits of Bomberman, bits of Pokemon maybe, and… Yup, some interesting imagery.

Oh Japan.

Still, I don’t want that to detract from what is genuinely a fun and interesting game, and the bits that have been translated certainly do help a lot in figuring out what’s going on. Another one that’s maybe worth firing up in an emulator - although perhaps not in front of the kids.

Again, I really loved the music in this game and just the general vibe of the PC-98 sound hardware, and YAHDI does include some music stuff which I’ve started to check out.

The PC-98 has always had a very active music scene and I mentioned earlier that YAHDI includes 3 different sound drivers known as FMP, MDX and PMD. It also includes a tracker called MSDP which looks really cool and supports all 3 formats but for some reason isn’t working on this machine and I promise I am going to try to get that working along with everything else as I learn more about it.

For now, here’s a small taste of things to come.

There’s also the built in image viewer that I mentioned and a .WAV file player to check out!

So hopefully you can see that I’m now pretty much up and running with this and working my way through various issues and learning as I go, which has been a lot of fun and that hopefully means that it won’t be quite so long until the next update on this machine - be sure to subscribe so you don’t miss those.

I’ve also been talking to another friend of the channel who has access to a professional data recovery lab who has very kindly offered to try to recover the original hard drive for me which would be really useful knowing what I now know about this machine. YAHDI does come with a copy of Windows 3.1 and I did briefly try to fire it up but it seems to hang, which I think is probably something to do with the graphics settings so I’ll definitely be checking that out as well as trying to get the original Windows 95 environment reconstructed and back up and running.

I’ve also just had this joystick adapter arrive from Japan. It’s Atari compatible and should even support 2 buttons with an MSX controller so I’ll need to see if I’ve got one somewhere that I can try out, or something that I can modify, and of course have a bit of a deeper dive into all of those games.

Oh, and you may have noticed in my last video that I didn’t actually get around to sticking those reproduction stickers back on to replace the originals that I took off for retrobrighting. It definitely isn’t because I lost them and have only just dug them out.

There! Now that looks the part.

So as always big thanks to my supporters on Ko-Fi, Patreon and the YouTube channel membership page for all of your support, you can see their names on screen as I speak - they got to see this video and others a little bit early and with the ads turned off as well as some other exclusive bits and bobs. But that’s all I have on the PC-98 for now, thank you ever so much for watching and I’ll hopefully see you - and this machine - again very soon.

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