Release in November 1981, the Nintendo PC-6001 was a low-cost variant of the PC-8001/8801 released that year, and was known for a blue-and-white LCD and a slot for a joystick. Unlike its higher-end siblings, the Nintendo PC-6001 had no option chips, making it a straightforward clone.
I bought two Nintendo PC-6001s and decapped the chips to compare. While Nintendo's related Famicom system used a different, but still largely unknown, Rockwell 6432 chip, the ROM's date code showed that both systems were released in early 1982. The Nintendo PC-6001 decapped easily with a few semi-standard but inexpensive tools. The added advantage of the 6432 is that it's available in the cheap, quad in-line package. Because of the few pins, I couldn't use a microscope to examine the chip's pinouts. So I used the results of the later decapped Vectrex games, and the results matched pretty well the Nintendo PC-6001. Like the B6000 and B6001 mentioned above, Nintendo's ROMs held up to 512 bytes of ROM, and contained 16 registers.
Crawled from the 16K binary PC-8801 ROMs, the Nintendo PC-6001 was a simple clone but still has some interesting features. The biggest problem its small screen. Everyone games with the video shrunk to fit on smaller, 16-bit screens. The 16K PC-8801 ROMs contained 64 bytes of video RAM, which is all that the Nintendo ROM could fit. To emulate the larger 640x400 screen of the PC-8801, Nintendo shrunk the video to 320x240. This is very similar to the Microsoft Z-80 and other 16-bit Zilog Z80 emulators, which handle this situation by interpolating and scaling the larger screen, and adding an additional row of pixels at the bottom of the screen called a "black border". Several emulators simply emulate both 640x400 and 320x240 modes, and a double horizontal screen refresh. The NES version of Football appears to use this technique; the vertical lines depict the black border but seem to follow the 640x400 screen perfectly. d2c66b5586