The National IMP-4 (originally National GPC/P) was a family of multi-chip 4-bit bit-slice microprocessor developed by National Semiconductor and introduced in 1973. Units could be combined to implement systems with 4 to 32-bit words. The IMP-8 and IMP-16 families were made using the IMP-4 logic. The IMP-4 had 2 chips: a control unit and an ALU, some systems used the RALU with custom control circuitry. The RALU was the first bit-slice microprocessor - predating both the 3000 and the am2900.
Rockwel was the only 2nd source for the IMP-4 series. Some USSR clones are known to exist.
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|IMP-4A/520||IMP-4A/420||Bundled Kit, CROM + RALU|
|IMP-4A/521||IMP-4A/421||Control and Read-only Memory (CROM)|
|IMP-00A/520||IMP-00A/420||Register and Arithmetic Logic Unit (RALU)|
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|designer||National Semiconductor +|
|full page name||national semiconductor/imp-4 +|
|instance of||integrated circuit family +|
|main designer||National Semiconductor +|
|manufacturer||National Semiconductor +|
|name||National IMP-4 +|
|process||10,000 nm (10 μm, 0.01 mm) +|
|word size||4 bit (0.5 octets, 1 nibbles) +|