Inside the Intel 1405: die photos of a shift register memory

In 1970, MOS memory chips were just becoming popular, but were still very expensive. Intel had released their first product the previous year, the 3101 RAM chip with 64 bits of storage.[1] For this chip (with enough storage to hold the word “aardvark”) you’d pay $99.50. To avoid these astronomical prices, some computers used the cheaper alternative of shift register memory. Intel’s 1405 shift register provided 512 bits of storage – 8 times as much as their RAM chip – at a significantly lower price. In a shift register memory, the bits go around and around in a circle, with one bit available at each step. The big disadvantage is that you need to wait for the bit you want to come around, which can take half a millisecond.

Great article.


    • 2014-12-23 3:56 pm
  1. 2014-12-23 7:17 pm
  2. 2014-12-24 6:32 pm
  3. 2014-12-25 12:19 am