1970s EPROM memory that still works!
I found this loose 1702A EPROM laying around today in the warehouse. Probably came from a 70s or 80s vintage Philips Transmission Electron Microscope since we still service those for people.
According to the National Museum of American History this is the first EPROM ever put on consumer market. For those that do not know EPROM stands for Erasable Programmable Read-Only Memory. These are the predecessors to the ubiquitous FLASH memory used today. Some like this one were gold plated for better conduction. The 1702 holds 2K of memory, and runs on 5 volts. It was invented by Dov Frohman of Intel in 1971! That means this chip may be older than me since I was born in 1973. So since I have heard that many of these still work, I decided to test it. Surprisingly, my programmer loaded some code onto it successfully as seen below.
Memory was stored in an array of floating gate transistors, each one holding a bit. The device could be erased by exposing it to Ultraviolet light for a few seconds. You can see in the picture a window, which was made of quartz, a UV transparent material. EPROMs were later replaced by EEPROMS, which are a electronically erasable version. EEPROMS with much larger storage capacity are still in production today, like the AT28C256 by Microchip Corp. It stores 256K of memory, in a 8x32K arrangement, with a 150 nanosecond access time. The 1702A by comparison has a 550 to 1000 nanosecond access time, depending on the type according to this spec sheet:
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I am intrigued that it still functions, and wanted to share. This was a robust device indeed, and I am not even sure how long this thing was cooking in the Texas heat in the warehouse.