Today we have a look around the outside of the Sega TeraDrive Model 2. It’s one of those lovely combinations of PC and Sega hardware that probably made perfect sense to somebody in Japan during the early 1990s.

The TeraDrive combines an IBM PC-compatible 80286 computer with Mega Drive hardware in the same chassis. Sega sold three models in Japan with different RAM and storage configurations. The Model 2 has 1 MB of PC-side RAM as standard and two floppy drives.

On the front there’s a switch for selecting PC or Mega Drive mode, along with a panel covering the two Mega Drive controller ports. The Model 1 has a single floppy drive, while the Model 3 trades one of the floppies for a hard drive. Having two drives on this one is rather nice when you’re playing around with DOS disks.

Around the back are the usual PC connections, alongside the Mega Drive video outputs and an RGB/composite arrangement. There’s also an expansion connector reminiscent of the early Mega Drive hardware. Sadly, the original serial-number label had disappeared before this particular machine came into my possession, so I can’t show you that.

The TeraDrive’s video switching is rather interesting, although not every modern monitor appreciates the signals it produces. My particular machine has also been fitted with extra RAM, bringing the displayed total to around 2.5 MB. The PC side uses a 286 running at about 10 MHz, which isn’t exactly spectacular performance, but it’s more than enough for a little DOS entertainment.

I’ve also fitted an XT-IDE compatible CompactFlash card, based on the open-source XT-CF-Lite version 4.1 design. Rather than buying a completed card, I had the PCBs manufactured, ordered the components and soldered them together myself. That included drag-soldering the fine-pitch CompactFlash connector, which worked out rather better than I might have expected. I built three of the cards without running into trouble. How’s that for a change?

This one had a 2 GB CompactFlash card installed, with the XT-IDE interface using address C800h. The firmware displayed build R588, dated 15 September 2015. Unfortunately, the card contained a version of Windows that wanted a 386 processor. Oh well. Wrong computer!

Testing the different video outputs was another adventure. Composite works, although the picture isn’t especially pleasant for reading PC text. The RGB arrangement is much sharper when the display accepts it, but I spent a fair bit of time changing switches and being greeted by an out-of-range message.

The Mega Drive side was considerably more cooperative. I inserted Sonic and flicked the front switch, and the game started up quite happily. It’s still wonderful seeing a Sega game running from a machine that looks so much like an IBM computer.

I also tried Wolfenstein 3D on the PC side. It ran, although I’d forgotten some of the controls and managed to get myself into trouble rather quickly. Apparently being able to boot DOS doesn’t automatically make me good at surviving a room full of enemies.

There are some obvious similarities to IBM machines of the period, including the PS/2 Model 25, Model 30 and IBM PS/1. That’s one of the things I particularly like about the TeraDrive’s appearance, and I’ll be getting into the hardware inside in a separate article.

I’ve also just worked out how to use the featured-image section for videos. Radical!

Edit: Aaaaaand now I’m not using featured anything anymore. Oh well! :P

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