Cyrix Corporation

National Semiconductor Corporation

Via-cyrix, Inc.

Convex Computer Corporation

Marc A Quattromani

Raul A Garibay, Jr

Mark W Bluhm

Mark W Hervin

Nital Patwa

Douglas Beard

Steven C McMahan

John K Eitrheim

Kevin M Lowderman

James A Jackson

A superscalar superpipelined microprocessor having a write buffer located between the core and cache is disclosed. The write buffer is controlled to store the results of write operations to memory until such time as the cache becomes available, such as when no high-priority reads are to be performed. The write buffer includes multiple entries that are split into two circular buffer sections for facilitating the interaction with the two pipelines of the core; cross-dependency tables are provided for each write buffer entry to ensure that the data is written from the write buffer to memory in program order, considering the possibility of prior data present in the opposite section. Non-cacheable reads form memory are also ordered in program order with the writing of data from the write buffer. Features for handling speculative execution, detecting and handling data dependencies and exceptions, and performing special write functions (misaligned writes and gathered writes) are also disclosed.

System and method of retiring misaligned write operands from a write buffer

Systems and methods for virtual addressing are disclosed having an address translation unit with variable page size by employing direct, victim, and programmable block translation look aside buffers. Selective comparisons between contents on a linear address bus and linear address tags are controlled by a size mask register which further controls a multiplexer to selectively steer bits onto a physical address bus from either the linear address bus or a physical address register.

Address translation unit employing programmable page size

A superscalar superpipelined microprocessor having a write buffer located between the core and cache is disclosed. The write buffer is controlled to store the results of write operations to memory until such time as the cache becomes available, such as when no high-priority reads are to be performed. The write buffer includes multiple entries that are split into two circular buffer sections for facilitating the interaction with the two pipelines of the core; cross-dependency tables are provided for each write buffer entry to ensure that the data is written from the write buffer to memory in program order, considering the possibility of prior data present in the opposite section. Non-cacheable reads from memory are also ordered in program order with the writing of data from the write buffer. Features for handling speculative execution, detecting and handling data dependencies and exceptions, and performing special write functions (misaligned writes and gathered writes). are also disclosed.

System and method of retiring store data from a write buffer

A system and method of readily identifying and handling self-modifying variable length instructions in a pipelined processor is disclosed employing index tags associated with each stage of the execution pipeline wherein the index tags identify the cache line numbers in the instruction cache from which the instructions originate.

Method of identifying and self-modifying code

An address translation unit is disclosed employing a direct-mapped translation lookaside buffer and a relatively small, associative victim translation lookaside buffer for translating linear addresses to physical addresses expediently and avoiding thrashing, without requiring large amounts of hardware and space.

Address translation unit employing a victim TLB

A superscalar superpipelined microprocessor having a write buffer located between the core and cache is disclosed. The write buffer is controlled to store the results of write operations to memory until such time as the cache becomes available, such as when no high-priority reads are to be performed. The write buffer includes multiple entries that are split into two circular buffer sections for facilitating the interaction with the two pipelines of the core; cross-dependency tables are provided for each write buffer entry to ensure that the data is written from the write buffer to memory in program order, considering the possibility of prior data present in the opposite section. Non-cacheable reads from memory are also ordered in program order with the writing of data from the write buffer. Features for handling speculative execution, detecting and handling data dependencies and exceptions, and performing special write functions (misaligned writes and gathered writes) are also disclosed.

Program order sequencing of data in a microprocessor with write buffer

Unified write buffer having information identifying whether the address

A shared interleaved memory having a relatively large number of banks employs circuitry and methodology for resolving bank conflicts without significantly inducing delay into the data path. A first and a second port make data read, data write, and instruction fetch requests to/from the shared interleaved memory by way of asserting a priority signal, an address, and an operand size which are decoded to discern which, if any, memory banks in the interleaved shared memory are needed. In the event of a bank request conflict, the highest priority requester gets all its requested banks and the losing requester gets all nonconflicting requested banks. After the banks in the interleaved memory are allocated, a signal identifying that the losing requester did not receive all its requested banks is generated which does not impact the delay in the data path and accordingly, the losing requester resubmits its request on the next cycle.

Interleaved memory conflict resolution with accesses of variable bank

A superscalar superpipelined microprocessor having a write buffer located between the core and cache is disclosed. The write buffer is controlled to store the results of write operations to memory until such time as the cache becomes available, such as when no high-priority reads are to performed. The write buffer includes multiple entries that are split into two circular buffer sections for facilitating the interaction with the two pipelines of the core; cross-dependency tables are provided for each write buffer entry to ensure that the data is written from the write buffer to memory in program order, considering the possibility of prior data present in the opposite section. Non-cacheable reads from memory are also ordered in program order with the writing of data from the write buffer. Features for handling speculative execution, detecting and handling data dependencies and exceptions, and performing special write functions (misaligned writes and gathered writes) are also disclosed.

Data dependency detection and handling in a microprocessor with write

An error correcting code and apparatus are used in conjunction with a main memory in which a data word is stored in a plurality of circuits each of which produces multiple outputs. A minimum number of check bits are stored together with the data word for detecting and correcting single bit errors and detecting the existence of multi-bit errors. A parity bit for the entire data word is also stored. For a 32-bit data word, at least 3 bits of the data word are stored in each of 10 memory circuits. Seven check bits and one parity bit are also stored in the 10 memory circuits wherein no more than one of the check bits or parity bit is stored in any one memory circuit. Upon reading the data word from the memory a set of verify check bits and a verify parity bit are generated and compared to the stored check bits and stored parity bit to produce a check bit syndrome and a parity bit syndrome. The check bit syndrome is decoded to produce an output that is input to an error generator circuit together with a parity syndrome for producing error signals indicating occurrence of a single bit error, a multi-bit error, a triple bit error, or a check bit error.

Growing community of inventors

Allen, TX, United States of America

Marc A Quattromani