Hacker News Reader

The TMS9900 was made in I²L bipolar technology, not MOS. Texas Instruments also had a 4 wide bitslice using the same fabrication process.

View on HN

You must confuse TMS9900 with other TI integrated circuits, perhaps those used for TMS990.

TMS9900, which was 16-bit CPU in a big 64-pin package (like that used later by Motorola MC68000) was certainly made in an NMOS technology.

See e.g. Wikipedia:

https://en.wikipedia.org/wiki/TMS9900

There is no doubt about this because TMS9900 required -5 V (for substrate bias), +5 V and +12 V (for enhancement MOS load transistors), like all early NMOS ICs, e.g. Intel 8080. No bipolar technology would have needed such power supplies.

The later TMS9995 was also made in an NMOS technology, but in a more modern variant with depletion transistor loads, which required only a single +5 V power supply, like Zilog Z80 and other more recent NMOS CPUs.

You are correct as is the other reply to my post. The chip in chapter 3 of the 1977 "The Bipolar Microcomputer Components Data Book" from Texas Instruments is the SBP9900 processor, not the TMS9900. I had never noticed this detail before and always had used this book as my reference for the 9900.

SBP9900 is the I²L version, found atleast in older M1 Abrams:

https://www.eevblog.com/forum/projects/reverse-engineering-a...

Reply on news.ycombinator.com