IBM PALM processor
Encyclopedia
The IBM PALM processor was a board-level 16-bit processor used in the IBM 5100 Portable Computer
, a predecessor of the IBM PC
. PALM was also used in the IBM 5110
and IBM 5120
follow-on machines. PALM was likely 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
to implement a higher-level instruction set
, rather than its conventional definition of a complete processor on a single silicon
integrated circuit
. The PALM processor was an entire circuit board containing 13 square metal-can bipolar
gate array
s, 3 conventional DIP
transistor-transistor logic
(TTL) parts and 1 round metal can part.
PALM has a 16-bit
data bus, with two additional bits used for parity
. PALM can directly address 64 kB (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 64 kB of RAM. A simple bank switching
scheme was used to extend the address space.
IBM 5100
The IBM 5100 Portable Computer was a portable computer introduced in September 1975, six years before the IBM PC. It was the evolution of a prototype called the SCAMP that was developed at the IBM Palo Alto Scientific Center in 1973. In January 1978 IBM announced the IBM 5110, its larger cousin,...
, a predecessor of the IBM PC
IBM PC
The IBM Personal Computer, commonly known as the IBM PC, is the original version and progenitor of the IBM PC compatible hardware platform. It is IBM model number 5150, and was introduced on August 12, 1981...
. PALM was also used in the IBM 5110
IBM 5110
The IBM 5110 Computing System was the successor of the IBM 5100 Portable Computer.Three variations of the IBM 5110 were built:* IBM 5110 Model 1 .* IBM 5110 Model 2 ....
and IBM 5120
IBM 5120
The IBM 5120 Computing System was announced in February 1980 as the desktop follow-on to the IBM 5110 Computing System...
follow-on machines. PALM was likely used in other IBM products as an embedded controller.
IBM referred to PALM as a microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
, though they used that term to mean a processor that executes microcode
Microcode
Microcode is a layer of hardware-level instructions and/or data structures involved in the implementation of higher level machine code instructions in many computers and other processors; it resides in special high-speed memory and translates machine instructions into sequences of detailed...
to implement a higher-level instruction set
Instruction set
An instruction set, or instruction set architecture , is the part of the computer architecture related to programming, including the native data types, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O...
, rather than its conventional definition of a complete processor on a single silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
integrated circuit
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
. The PALM processor was an entire circuit board containing 13 square metal-can bipolar
Bipolar junction transistor
|- align = "center"| || PNP|- align = "center"| || NPNA bipolar transistor is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications. Bipolar transistors are so named because their operation involves both electrons...
gate array
Gate array
A gate array or uncommitted logic array is an approach to the design and manufacture of application-specific integrated circuits...
s, 3 conventional DIP
Dual in-line package
In microelectronics, a dual in-line package is an electronic device 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 or inserted in a socket.A DIP is usually referred to as a DIPn, where n is...
transistor-transistor logic
Transistor-transistor logic
Transistor–transistor logic is a class of digital circuits built from bipolar junction transistors and resistors. It is called transistor–transistor logic because both the logic gating function and the amplifying function are performed by transistors .TTL is notable for being a widespread...
(TTL) parts and 1 round metal can part.
PALM has a 16-bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
data bus, with two additional bits used for parity
Parity bit
A parity bit is a bit that is added to ensure that the number of bits with the value one in a set of bits is even or odd. Parity bits are used as the simplest form of error detecting code....
. PALM can directly address 64 kB (64 KiB
Kibibyte
The kibibyte is a multiple of the unit byte for quantities of digital information. The binary prefix kibi means 1024; therefore, 1 kibibyte is . The unit symbol for the kibibyte is KiB. The unit was established by the International Electrotechnical Commission in 1999 and has been accepted for use...
) of memory. The IBM 5100 could be configured with up to 64+ kB (APL + BASIC ROMs make 64+ kB) of Executable ROS (ROM
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
) and up to 64 kB of RAM. A simple bank switching
Bank switching
Bank switching is a technique to increase the amount of usable memory beyond the amount directly addressable by the processor. It can be used to configure a system differently at different times; for example, a ROM required to start a system from diskette could be switched out when no longer...
scheme was used to extend the address space.