Logic Chip, Module, And Board Design - IBM 4381 Manual

and the cooling process used in 4381 Processors had not been implemented in IBM
processors before the 4381.
The multilayer logic board design first used in the 3081 Processor Unit is also used
in the 43 81 Processor. The logic module packaging and logic module board design
for the 4381 Processor eliminate an entire level of packaging, aid logic reliability,
and increase logic speed relative to the 4341 implementation. Logic in the 4381
utilizes advanced features that were first used to package logic chips in other 4300
Processors but extends these features to significantly increase the circuit density of
a substrate.
Logic wiring in IBM processors other than the 4381, 308X, and 3090 occurs at
several levels. First, elementary components (transistors, diodes, and resistors) on
a chip are connected to form circuits, which are then interconnected at the chip
level. Additional circuit connections are then made at the logic module level (that
is, within the substrate) and at the card level. Cards are mounted on boards
(card-on-board packaging) and circuit connections among the cards on the same
board and among cards on different boards are made via cabling. This design is
used in 4300 Processors other than 4381 Processors.
Card-on-board packaging is not used for most of the logic in the 4381 Processor
unit. Instead, logic modules are mounted directly on a multilayered board, which
provides the ability to interconnect the logic modules on the board via imbedded
wiring, thus eliminating most intraboard cabling.
Logic Chip, Module, and Board Design
The logic chip used in the 4381 Processor unit is 4.57 by 4.57 millimeters
(approximately 3/16 of an inch square) and contains over 7000 elementary
components (resistors, diodes, and transistors). The 7000 elementary compone,1ts
on a chip can be connected to form a maximum of 704 logic circuits.
The logic chip for the 43 81 Processor has the same maximum logic circuit capacity
(704) as the chip used in other 4300 Processors. However, a slightly different
technology than is used for the 704-circuit chip in 4341 Processors is used for the
4381 chip. This technology reduces the size of the transistors on a 4381 chip and
more power is used. These differences result in a 4381 chip circuit speed that is
1.15 nanoseconds for 4381 Model Groups 11, 12, 1, 2, and 3 (approximately
one-half that of the 4341 Model Group 2 logic chip) and a chip circuit speed of .7
nanoseconds for 4381 Model Groups 13 and 14.
Of the 704 circuits available on a single chip, the average number actually utilized
in the logic implemented in the 43 81 Processor is 650. The high circuit utilization
per chip is made possible in part because three layers of wiring are used for
interconnections on the chip itself. A logic chip in the 43 81 Processor can contain
several feet of wire that interconnects the elementary components and circuits on
the chip.
The 43 81 logic chips are mounted on a multilayer ceramic substrate that is 64
millimeters (about 2.5 inches) square and 5.5 millimeters (.2 of an inch) thick,
which is larger than the ceramic substrate for 4341 Processor logic (SO millimeters
by 50 millimeters or approximately 2 inches square) but smaller than the ceramic
substrate for the 3081 logic module (90 millimeters, about 3.5 inches, square).
Section 10: Technology and Architecture
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