The PALM (Program All Logic in Microcode) is a 16-bit

central processing unit A central processing unit (CPU), also called a central processor, main processor, or just processor, is the primary Processor (computing), processor in a given computer. Its electronic circuitry executes Instruction (computing), instructions ...

(CPU) developed by IBM. It was used in the IBM 5100 Portable Computer, a predecessor of the

IBM PC The IBM Personal Computer (model 5150, commonly known as the IBM PC) is the first microcomputer released in the List of IBM Personal Computer models, IBM PC model line and the basis for the IBM PC compatible ''de facto'' standard. Released on ...

, and the IBM 5110 and IBM 5120 follow-on machines. It is likely PALM was also used in other IBM products as an embedded controller.

IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...

referred to PALM as a ''microprocessor'', though they used that term to mean a processor that executes

microcode In processor design, microcode serves as an intermediary layer situated between the central processing unit (CPU) hardware and the programmer-visible instruction set architecture of a computer. It consists of a set of hardware-level instructions ...

to implement a higher-level

instruction set In computer science, an instruction set architecture (ISA) is an abstract model that generally defines how software controls the CPU in a computer or a family of computers. A device or program that executes instructions described by that ISA, s ...

, rather than its conventional definition of a CPU on an

integrated circuit An integrated circuit (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components a ...

. The PALM processor was a circuit boardsalvaging a huge IBM 1130 APL program containing 13 bipolar

gate array A gate array is an approach to the design and manufacture of application-specific integrated circuits (ASICs) using a semiconductor device fabrication, prefabricated chip with components that are later interconnected into logic devices (e.g. NAN ...

s packaged in square metal cans, 3 conventional

transistor–transistor logic Transistor–transistor logic (TTL) is a logic family built from bipolar junction transistors (BJTs). Its name signifies that transistors perform both the logic function (the first "transistor") and the amplifying function (the second "transistor" ...

(TTL) ICs in

dual in-line package In microelectronics, a dual in-line package (DIP or DIL) is an Semiconductor package, electronic component package with a rectangular housing and two parallel rows of electrical connecting pins. The package may be through-hole technology, throu ...

s, and 1 round metal can part. The PALM was used to implement an emulator, which in turn could run machine instructions originally written for other machines; this is how

IBM System/360 The IBM System/360 (S/360) is a family of mainframe computer systems announced by IBM on April 7, 1964, and delivered between 1965 and 1978. System/360 was the first family of computers designed to cover both commercial and scientific applicati ...

APL ran on the ''5100''. PALM has a 16- bit data bus, with two additional bits used for parity. PALM can directly address 64KB (64 KiB) of memory. The IBM 5100 could be configured with up to 64+KB (APL + BASIC ROMs make 64+KB) of ''Executable ROS'' (

ROM Rom, or ROM may refer to: Biomechanics and medicine * Risk of mortality, a medical classification to estimate the likelihood of death for a patient * Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac * ...

) and up to 64KB of RAM. A simple bank switching scheme was used to extend the address space. In 1973, the IBM Los Gatos Scientific Center developed a portable computer prototype called SCAMP (Special Computer APL Machine Portable) based on the PALM processor with a Philips compact cassette drive, small CRT display, and full-function keyboard.TOSEC: IBM PC Compatibles (2012-04-23)
Internet Archive

References

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External links

about various Microcode implementations
;Pictures

The Maintenance Information Manual linked at the bottom of the page includes an appendix describing the microcode. PALM IBM microprocessors