The PALM (Put 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 electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, a ...

(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 IBM PC model line and the basis for the IBM PC compatible de facto standard. Released on August 12, 1981, it was created by a team ...

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

microcode In processor design, microcode (μcode) is a technique that interposes a layer of computer organization between the central processing unit (CPU) hardware and the programmer-visible instruction set architecture of a computer. Microcode is a lay ...

to implement a higher-level

instruction set In computer science, an instruction set architecture (ISA), also called computer architecture, is an abstract model of a computer. A device that executes instructions described by that ISA, such as a central processing unit (CPU), is called ...

, rather than its conventional definition of a CPU on an

integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny M ...

. 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 prefabricated chip with components that are later interconnected into logic devices (e.g. NAND gates, flip-flops, etc.) accordin ...

packaged Packaging is the science, art and technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of designing, evaluating, and producing packages. Packaging can be described as a co ...

in square metal cans, 3 conventional

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

(TTL) ICs in

dual in-line package In microelectronics, a dual in-line package (DIP or DIL), is an electronic component package with a rectangular housing and two parallel rows of electrical connecting pins. The package may be through-hole mounted to a printed circuit board (P ...

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 that was announced by IBM on April 7, 1964, and delivered between 1965 and 1978. It was the first family of computers designed to cover both commercial and scientific applica ...

APL ran on the ''5100''. PALM has a 16-

bit The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represented ...

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) and up to 64KB of

RAM Ram, ram, or RAM may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch ...

. A simple

bank switching Bank switching is a technique used in computer design to increase the amount of usable memory beyond the amount directly addressable by the processor instructions. It can be used to configure a system differently at different times; for exampl ...

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

{{reflist

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 Palm most commonly refers to: * Palm of the hand, the central region of the front of the hand * Palm plants, of family Arecaceae **List of Arecaceae genera * Several other plants known as "palm" Palm or Palms may also refer to: Music * Palm (ba ...

IBM microprocessors