5061

The HP desktop calculator 9825 uses a multi-chip hybrid module as the core of its computing capability. This hybrid module consists of three chips combined on a ceramic substrate along with a number of support chips. This combination of chips works together to form a full 16-bit minicomputer-class CPU, with an instruction set similar to that of HP's 211x-series minicomputers.
The 5061 consists of three secondary NMOS chips:

- BPC (Binary Processor Chip): decodes and executes 59 instructions; central unit of
                                               the processor; directs the other two chips; contains
                                               the general purpose 16 bit registers A and B and a
                                               program counter P; a stack pointer and flags are also
                                               implemented on this chip.
- IOC (Input Output Chip): performs I/O via 12 instructions.
- EMC (Extended Math CHip): performs 15 instructions mostly involving Binary Coded
                                             Decimal math.
All chips are packaged in a small hybrid circuit with several buffer chips; registers on the processor chips are memory mapped allowing communications between the chips through a 32 word window in memory; memory was word-addressed and therefor required only 15 bits to address 64K bytes.