951x > AMDAM9511ADC_2
Modified: March 11, 2005, 11:27 pm
Manufacturer:AMD
Model:AM9511ADC
Speed:2MHz
Type:9511
Data Code:8334
Introduced:1979
Transistors:??
Package:24CDIP
Process:3 Micron
Architecture:FPU
Used in:CP/M, S-100, Others
Description:.
AMD also produced what is probably the first
floating point "coprocessor" for microprocessors,
the AMD 9511 "arithmetic circuit" (1979), which
performed 32 bit (23 + 7 bit floating point) RPN-
style operations (4 element stack) under CPU
control - the 64-bit 9512 (1980) lacked the
transcendental functions. It was based on a 16-
bit ALU, performed add, subtract, multiply, and
divide (plus sine and cosine), and while faster
than software on microprocessors of the time
(about 4X speedup over a 4MHz Z-80), it was much
slower (at 200+ cycles for 32*32->32 bit
multiply) than more modern math coprocessors are.

It was used in some CP/M (Z-80) systems, and on a
S-100 bus math card for NorthStar systems.
Calculator circuits (such as the National
Semiconductor MM57109 (1980), actually a 4-bit NS
COP400 processor with floating point routines in
ROM) were also sometimes used, with emulated
keypresses sent to it and results read back, to
simplify programming rather than for speed.