Putting The Sega Teradrive Into Overdrive

During the 80s and 90s it seemed like Japan got all the good stuff when it came to videogames. In the US there were consoles called the NES, the TurboGrafx-16, and the Genesis. While in Japan they had cooler names like: the Famicom, the PC Engine, and the Mega Drive. The latter was incorporated into a plethora of different form factors, including the little known IBM PC/Mega Drive combo known as the Sega Teradrive. Finding a rare Japanese 1990s PC stateside is a feat in and of itself, and thanks to an electronics hobbyist named [Ronnie] there is at least one Teradrive out there still running strong thanks to an upgraded CPU mod.

Sega Teradrive Motherboard CPU

In theory, the Sega Teradrive was a dream-machine; combining the utility of an IBM PC with the fun of a Sega Mega Drive. The dual functionality extended to the video modes where both VGA and composite video were supported. However, the reality was that the final design was less than desirable. The Teradrive shipped in 1991 with an Intel 80286, 16-bit processor which was already two processor generations behind at the time. The meager 10Mhz clock speed was on the lower end of the performance spectrum which meant that many DOS titles ran poorly…or not at all.

Not satisfied with those specs, [Ronnie] modded his Teradrive with an adapter board containing an Intel 80486 processor clocked at 66Mhz. The upgrade, accompanied with a complete re-cap of the motherboard, brings the IBM PC to 486DX status. This opened up a few new possibilities including the Thundercats Demo in the video below:

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A Modern 386 Development Board

Some readers out there probably have nostalgic feelings for their first 386 based PC, the beeps and hisses of the modem, and the classic sound of a floppy drive’s stepper motor. Perhaps that turbo button that we could never quite figure out.

If you want the power of a 386 processor today, you’re in luck: [Pierre Surply] has developed a modern development board for the 80386SX CPU. This board is based on a 386 processor that comes in a LQFP package for “easy” soldering, and an Altera Cyclone IV FPGA.

To allow the CPU to run, the FPGA emulates the chipset you would usually find on a PC motherboard. The FPGA acts as both a bus controller and a memory controller for the CPU. On the board, there’s an SRAM chip and internal memory on the FPGA, which can be accessed through the 386’s bus access protocol.

The FPGA also provides debugging features. A supervisor application running on the FPGA gives debugging functionality via a FTDI USB to UART chip. This lets you control operation of the CPU from a PC for debugging purposes. The FPGA’s memory can be programmed through a JTAG interface.

The project is very well documented, and is a great read if you’re wondering how your old 386 actually worked. It can even be hand soldered, so the adventurous can grab the design files and give it a go. The francophones reading can also watch the talk in the video below.

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