Browse Prior Art Database

Fixed Point Overflow Exception Detection

IP.com Disclosure Number: IPCOM000048038D
Original Publication Date: 1981-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 12K

Publishing Venue

IBM

Related People

Hedeman, WR: AUTHOR

Abstract

The performance of a data processing machine is enhanced by providing automatic hardware detection of fixed point overflow conditions.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 69% of the total text.

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Fixed Point Overflow Exception Detection

The performance of a data processing machine is enhanced by providing automatic hardware detection of fixed point overflow conditions.

Three mechanisms are provided in order to allow access of the microcode to the hardware overflow logic and indicators: 1) An extension is added ot the condition code setting

micro-order to allow setting of the fixed point over

overflow condition.

2) A hardware register,'set during any program status

switch, is added to the logic.

3) A micro-code resettable and readable fixed point

overflow indicator is added to the logic of the

machine.

In addition to the microcode accessible logic, a trap condition is added to the hardware in order to intercept the overflow condition without microcode inspection. In addition to causing the trap condition, this logic sets the fixed point overflow condition at the time the overflow condition is detected.

Four micro-orders are introduced for the purpose of allowing micro-code access of the logic: PMWR sets the program mask register from the byte

logic unit (mover).

OVFLSTAT permits setting or resetting of the fixed point

verflow status indicator under microcode

control.

FPOV is a branch point that allows microcode

interrogation for a fixed point overflow

condition.

CCALG is an existing micro-order which has been

extended to include a set of the fixed point

overflow indicator and to force the trap

condition.

Changes are made in the microcode in order to perfor...