Ultra rare 3 inch Silicon Wafer - The 1970s Bell Labs BellMAC-4 CPU

Description

The predecessor of the modern DSP, the BellMAC-4 (also known as the MAC-4) was created by Bell Laboratories in the 1970s. This special gem is a great piece of DSP/CPU history and is called by some the first single chip DSP. I was able to purchase these for my collection from the estate of a former Bell Labs engineer. So far as I can tell, they are the only wafers of this type on the market.
During the 1970's Bell Laboratories was fertile ground for the imaginations of engineers fortunate enough to work there. Aside from their work in microelectronics fabrication, the "C" programming language was simultaneously being developed at Bell Labs and the resulting code run on the very processors they were building.
Creation of this CPU was a natural direction to take as the idea of putting CPUs into telephones came about. Ironically the 4 bit MAC-4 was a technologically advanced derivative of the BellMAC-8 (8 bit CPU) developed for use in telephony applications. Dropping line widths from the 5 microns (BellMac-8) to 3.5 microns, allowed the MAC-4 to have on chip ROM and RAM, making it an embeddable microcomputer.
With all these elements coming together at one time and place, Bell engineers saw the future of digital signal processing. The idea of the MAC (Multiply Accumulate) unit was carried over into a line of processors they named DSPs the first of which is DSP1 which had the basic computing features of a modern DSP. Skipping beyond the 16 bit generation altogether, they developed the BellMac-32 (WE 32100) CPU and also the WE DSP32 (32 bit DSP).
Die photo credit to Pauli Rautakorpi
Note:  The BellMAC-8 (WE 212) was used strictly internal to Bell.
See the WE DSP32 and many other tech collectables in my ebay store.