IBM PALM processor
| Company type | Microprocessor design |
|---|---|
| Industry | Computer hardware |
| Founded | 1973 |
| Founder | IBM |
| Products | 16-bit CPU used in IBM 5100, 5110, and 5120 |
| Parent | IBM |
The PALM (Program All Logic in Microcode) is a 16-bit central processing unit (CPU) engineered by IBM. It was utilized in the IBM 5100 Portable Computer, an early forerunner to the IBM PC, as well as in its successors, the IBM 5110 and IBM 5120. Additionally, it is believed to have functioned as an embedded controller within other IBM devices.
IBM characterized PALM as a microprocessor, indicating a processor that interprets microcode to execute a higher-level instruction set, rather than being a CPU contained within a single integrated circuit. The PALM unit comprised a circuit board equipped with thirteen bipolar junction transistor gate arrays housed in metal packages, three standard transistor–transistor logic (TTL) integrated circuits, and one extra metal-can component.
This processor incorporated an emulator enabling it to run machine instructions from alternative systems; most notably, it supported IBM System/360 APL on the 5100 model.
The architecture includes a 16-bit data bus accompanied by two parity bits and supports direct addressing of up to 64KB of memory. The IBM 5100 could be outfitted with more than 64KB of Executable ROS (ROM) containing both APL and BASIC languages, alongside a maximum of 64KB RAM. To surpass this memory limit, a bank switching mechanism was employed to expand the accessible address space.
In 1973, IBM’s Los Gatos Scientific Center developed the SCAMP (Special Computer APL Machine Portable) prototype based on the PALM CPU. This prototype featured a Philips compact cassette drive, a compact CRT display, and a full keyboard.
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