Compaq Computer Corporation, Inc.

Gary L Brasher

James H Nuckols

Paul R Culley

Theodore F Emerson

Gary W Thome

Jeffrey S Watters

Roger A Kaiser

A data field having a variable number of zero-level bits is read by a bus in a digital system, wherein the bus is pumped by writing all logical 'one' bits onto the bus lines just before they are read. The unused bits will then be still in a logical 'one' state, i.e. a known value, rather than floating or at an indeterminate value. A program for performing this operation in a computer uses steps to prevent other operations such as refresh cycles or interrupts from being interposed between the write and read cycles. A CPU may use this method to read a system identifier value upon boot-up, for example.

Pump bus to avoid indeterminacy in reading variable bit field

A computer system uses a random access memory to store memory characteristic information, such as noncacheable status. The memory is coupled to the processor address lines to produce an output representative of the memory address block, the output used as appropriate, for example by the noncacheable address input of a cache controller. Latches are used to store programming mode, write or read operation and data values. The reading and writing of the random access memory is performed without disturbing the main memory.

Noncacheable address random access memory

A computer having an improved keyboard/auxiliary device interface controller which supports the selective restriction of user interaction with the computer system, while maintaining the full internal functionality of the host/peripheral interface. A 'password lock mode' of the improved controller prevents users from gaining unauthorized access to the computer system, but still application and operating system software can continue to issue commands to and receive responses from the otherwise disabled peripheral devices. The improved controller does not require modification to the conventional keyboard/auxiliary device hardware.

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Houston, TX, United States of America

Gary L Brasher