International Business Machines Corporation

Michael J DeLoye

Dennis L Moeller

Daniel P Fuoco

Roger L Cox

Robert L Myers

In a personal computing system the function of the DMA controllers in the 'AT' or 'ISA' bus has been modified so that the system may select whether the 16-bit DMA channels are to be used as 8-bit DMA channels or 16-bit DMA channels. An 8/16-bit mode bit for each of the 16-bit DMA channels is written in a control register during the system Power On Self Test routine. Once the mode bit is written for each of the three 16-bit DMA channels, it may be read when the channel is active to select whether the channel is to operate as an 8-bit or 16-bit channel. With this mode bit information available, the page addressing may be selectively changed from 128k size pages to 64k size pages when a 16-bit DMA channel is to be converted to 8-bit. In addition, the byte addressing within a page may be changed from two byte addressing during 16-bit mode to single byte addressing during 8-bit mode.

Selectable 8/16 bit DMA channels for 'ISA' bus

This invention relates to personal computers, and more particularly to personal computer power supplies for supplying electrical power to electrically operated components which manipulate or store digital data. The power supply has a controllable component for responding to the presence and absence of a low voltage direct current electrical signal by enabling and disabling the supply of electrical power to the data processing and storage components, and a signal generator circuit operatively connected with the controllable component and with an alternating current electrical main supply for controllably deriving from the main supply a low voltage direct current signal for delivery to the controllable component, whereby a user of the microcomputer may control energization of the electrically powered data processing and storage components by controlling the application of the low voltage direct current signal from the signal generator circuit to the controllable component.

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Boynton Beach, FL, United States of America

Michael J DeLoye