Section 10: Technology And Architecture; 10:05 Technology; Introduction - IBM 4381 Manual

Section 10: Technology and Architecture
10:05 Technology
Introduction
The price performance and compact size of the 4381 Processor unit have been
achieved in part through the use of large-scale integrated bipolar semiconductor
technology for logic chips and large-scale integrated packaging of logic chips. In
addition, a 64K-bit and 256K-bit dynamic storage chip are used for processor
storage.
Large-scale integrated technology and packaging are utilized to increase logic
circuit density. The major benefits of increased circuit density are faster logic
speed and higher logic reliability. In addition, logic cost and space requirements are
reduced.
The speed of logic circuitry is affected by the distance signals have to travel. The
shorter the distance, the less the time it takes for the signals to travel from one
circuit to another, and at the same time less power is consumed. The use of less
power reduces the total amount of heat generated by the circuitry, which reduces
the total amount of cooling required. However, the higher density of circuits
concentrates the heat that is generated in a smaller area.
The reliability of logic circuitry is related to the ( 1) number of circuit
interconnections and (2) level of packaging (location and wire length) at which the
interconnections occur (which determines the number of times an electrical current
must flow between dissimilar materials). External connections (the wiring among
circuits) are the least reliable part of logic circuitry. Thus, circuit connections made
on a chip are more reliable than those made off a chip. Reductions in the number
and length of external connections (those made off the chip via a card or board, for
example) improve reliability.
The large-scale integrated (LSI) technology in which the logic in the 43 81
Processor is implemented is very similar to the LSI technology implemented in
4341 Processors but provides faster circuit speeds. The packaging of 4381 logic
chips on a ceramic substrate is an extension of the packaging used in 4341
Processors and is similar to the packaging used for 308X logic modules; however,
fewer chips are placed on a substrate for the 4381 Processor than for the 308X
Processor Unit to reduce cooling requirements. The packaging of a logic module
14
A Guide
to the
IBM 4381
Processor