There are a lot of great tools and games available for the NEC PC-6001 (1981.) However, the original models, including the US-market NEC TREK, often require a 16K RAM expansion to be able to run advanced software. There are official NEC options, such as the NEC PC-6006 cartridge, but these are expensive and becoming rarer.

This hardware was developed as part of a Leaded Solder blog post, which is still upcoming. In the meantime, you can read about how I used this cartridge to play some homebrew games.

With any luck, a case design will soon be forthcoming, but if you design one yourself, please let me know! It would save me a lot of work.

Ordering Suggestions

Because this is a cartridge with an edge connector, it's a great idea to get a beveled edge, as well as ENIG or Hard Gold finishing, if you can afford it. These will put less strain on your cartridge slot and make the cartridge last much longer before corroding.

Build Instructions

1. Solder pin headers into the pin header locations.
2. Solder two 28-pin DIP sockets into the cartridge. You can use a ZIF-socket for the ROM, but keep in mind that the lever will keep you from being able to insert it into the PC-6001, and you will have to use an expansion module such as a PC-6011 instead.
3. Solder down the 74-series ICs. You can use a socket if you want.
4. Install the 62256 RAM chip. This is designed around the Cypress CY62256 SRAM, but other 62256-compatible SRAMs are available, sometimes with slightly different pinouts. It is not necessary to get an exact match to the pinout: even if the address pins are numbered differently, it will still work as long as the computer can place data and retrieve data at the same address. Set the jumper to enable SRAM.
5. Program the 27C256 with your software. Insert the 27C256 and set the jumper for hi/low half of the ROM.
6. Insert the cartridge into your PC-6001 (with the power turned off) and start the computer up. It should begin running the software that is loaded on ROM.

Special Thanks

The following blog posts and articles were essential for me to figure this out. Thank you for your hard work.

• tsutsui's 32K RAM cartridge design;
• mm's 32K RAM/ROM cartridge design;
• Nishida Radio's Beluga mega-ROM cartridge. Thank you most of all, Nishida-san, for getting me into the world of homemade 8-bit computer hardware.