Browse Prior Art Database

Enabled Stack Expansion Routine

IP.com Disclosure Number: IPCOM000080445D
Original Publication Date: 1973-Dec-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Davidson, GA: AUTHOR

Abstract

This program provides for the simultaneous enabled addition of elements to a `pop-up' stack.

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Enabled Stack Expansion Routine

This program provides for the simultaneous enabled addition of elements to a `pop-up' stack.

Consider the `pop-up' stack arrangement shown in Fig. 1. The beginning of the stack is fixed, while a control word contains the current address of the last stack element. The elements of the stack are contiguous words. The high-order bit of the last element is set to 1 to facilitate sequential processing of the entire stack.

The stack is expanded by adding elements one at a time to the bottom, and compressed by removing elements singly or collectively at the top via up-shifting the desired number of words. Performing these operations disabled preserves the integrity of the stack, but may impose severe performance implications. This is due to overhead involved in changing to and from the disabled state. In addition, increased processing activity on the stack causes a proportional increase in disabled time, which may result in a backlog of interrupts.

This routine eliminates the above expansion overhead by allowing the function to be performed enabled. The application can reduce compression overhead by processing the entire stack before requesting compression. It should be noted that stack compression must not occur concurrently with stack expansion.

Fig. 2 contains the flow chart of the Enabled Stack Expansion Routine. First, the current last element address is gotten and internally updated to reflect the new element to be added to the stack...