CPU of the Day: Scientific Micro Systems SMS300
Over two years ago we wrote about the history of the Signetics 8X300 processor. A design that was one of the first DSP like architectures. The 8X300 was a design of the Scientific Micro Systems Inc. SMS300. You can read the entire history here.
The only SMS300 I had ever seen was a picture of one in the 1976 issue of Microcomputer Digest (as seen here). Its a very unusual package, with very long leads. Recently I found one hiding in a scrap lot on eBay, and could nearly not contain my excitement when the seller confirmed its markings. Of course I purchased the scrap lot, and waited like a child before Christmas for it to arrive. When it did, I was happily surprised to find it intact, and in good condition (a relatively rare occurrence for a DIP in a scrap lot, especially a 36 year old one.
SMS 300 – Early 1976
Here you can see an original SMS300 dating from 1976. Interestingly enough the Signetics version is in a 50 pin package while the SMS is in a 48pin. I assume Signetics changed some of the power supply requirements for it but do not know for sure.
Back side showing stunning traces and die caps
Looking at the back of the processor you can see 2 large ceramic ‘caps’, one is for the die, the other appears to be a power circuit of some sort. These are over 2mm thick, which is one of the reasons for the very long pins. (8 mm long). If you have any additional info on the SMS300 (a datasheet perhaps) please let me know.
March 18th, 2014 at 4:42 pm
[…] of in the 1970′s. Some of these processors never saw wide use in PCs, such as the 1802 or SMS300 yet were remarkable. Still others were designed not to be mass market, or to be licensed but to […]
August 16th, 2022 at 8:09 am
The extra “bump” on the SMS package is a NPN pass transistor, probably the die from a 2N5320. It is used to step-down the 5 volts. Signetics added two extra pins and placed this transistor outboard.