A microprocessor system is disclosed having a high speed system bus for coupling system elements, and having a dual bus microprocessor with separate ultra-high speed instruction and data cache-MMU interfaces coupled to independently operable instruction and data cache-MMU, respectively. A main memory is coupled to the system bus for selectively storing and outputting digital information. The instruction and data cache-MMU's are coupled to the main memory via the system bus for independently storing and outputting digital information to respective mapped addressable very high speed cache memory. The microprocessor is coupled via separate and independent very high speed instruction and data buses to each of the instruction cache-MMU and data cache-MMU, respectively, for processing data received from the data cache-MMU responsive to instructions received from the instruction cache-MMU. The instruction bus and data bus are exclusive and independent of one another, and allow for simultaneous very high-speed transfer. The data cache-MMU and instruction cache-MMU each have separate dedicated system bus interfaces for coupling to the main memory and to other peripheral devices which are coupled to the system bus. Numerous other system elements can also be coupled to the system bus, including an interrupt controller, an I/O processor, a bus arbiter, an array processor, and other peripheral controller devices.

Apparatus for maintaining consistency of a cache memory with a primary memory

In a cache memory system, multiple-word boundary registers, multiple-word line registers, and a multiple-word boundary detector system provide accelerated access of data contained within the cache memory within the multiple-word boundaries, and provides for effective prefetch of sequentially ascending locations of stored data from the cache memory. In an illustrated embodiment, the cache memory stores four words per addressable line of cache storage, and accordingly quad-word boundary registers determine boundary limits on quad-words, quad-word line registers store, in parallel, a selected line from the cache memory, and a quad-word boundary detector system determines when to prefetch the next set of quad-words from the cache memory for storage in the quad-word line registers.

Quadword boundary cache system

A cache and memory management system architecture and associated protocol is disclosed. The cache and memory management system is comprised of a set associative memory cache subsystem, a set associative translation logic memory subsystem, hardwired page translation, selectable access mode logic, and selectively enableable instruction prefetch logic. The cache and memory management system includes a system interface for coupling to a systems bus to which a main memory is coupled, and is also comprised of a processor/cache bus interface for coupling to an external CPU. As disclosed, the cache memory management system can function as either an instruction cache with instruction prefetch capability, and on-chip program counter capabilities, and as a data cache memory management system which has an address register for receiving addresses from the CPU, to initiate a transfer of defined numbers of words of data commencing at the transmitted address. Another novel feature disclosed is the quadword boundary, quadword line registers, and quadword boundary detector subsystem, which accelerates access of data within quadword boundaries, and provides for effective prefetch of sequentially ascending locations of storage instructions or data from the cache memory subsystem.

Cache MMU system

A microprocessor architecture is disclosed having separate very high speed instruction and data interface circuitry for coupling via respective separate very high speed instruction and data interface buses to respective external instruction cache and data cache circuitry. The microprocessor is comprised of an instruction interface, a data interface, and an execution unit. The instruction interface controls communications with the external instruction cache and couples the instructions from the instruction cache to the microprocessor at very high speed. The data interface controls communications with the external data cache and communicates data bidirectionally at very high speed between the data cache and the microprocessor. The execution unit selectively processes the data received via the data interface from the data cache responsive to the execution unit decoding and executing a respective one of the instructions received via the instruction interface from the instruction cache. In one embodiment, the external instruction cache is comprised of a program counter and addressable memory for outputting stored instructions responsive to its program counter and to an instruction cache advance signal output from the instruction interface. Circuitry in the instruction interface selectively outputs an initial instruction address for storage in the instruction cache program counter responsive to a context switch or branch, such that the instruction interface repetitively couples a plurality of instructions from the instruction cache to the microprocessor responsive to the cache advance signal, independent of and without the need for any intermediate or further address output from the instruction interface to the instruction cache except upon the occurrence of another context switch or branch.

Method and apparatus for addressing a cache memory

A microprogrammed data processing system is provided in which each high level instruction is performed by one or more tasks, each task being in turn performed by executing one or more task microinstructions in a microprogrammed manner. Dynamic resource allocation is provided by employing a plurality of dynamically allocatable registers whose free and use states are continuously monitored in an allocation register. The outputs of the allocation register are used as an address for a register allocation memory which is mapped so as to identify a particular group of free registers which are available for assignment for each new task in response to the allocation register address.

Microprogrammed digital data processor employing microinstruction tasking and dynamic register allocation

A digital processor including both macro and micro instruction generators. The micro-instruction generator comprises a sequencer for generating instruction addresses, a memory for generating instructions in response to the addresses and a pipeline register adapted to receive the instructions for execution. The sequencer operates at a constant CLK 1 rate while the pipeline register operates at a variable CLK 2 rate; i.e., the occurrence of a branch instruction in the pipeline register operates to inhibit CLK 2 for one CLK 1 time so as to prevent loading for execution of the aborted sequential instruction during the loading of a new non-sequential instruction address. CLK 2 resumes upon the next CLK 1 signal to resume sequential operation. Special branch instructions are utilized to fetch macro-instructions from a pipelined system of macro-instruction registers. A two-tier synchronous arbitration system for memory requests is also disclosed.

High-speed synchronous computer using pipelined registers and a two-level fixed priority circuit

A digital processor including both macro and micro instruction generators. The micro-instruction generator comprises a sequencer for generating instruction addresses, a memory for generating instructions in response to the addresses and a pipeline register adapted to receive the instructions for execution. The sequencer operates at a constant CLK 1 rate while the pipeline register operates at a variable CLK 2 rate; i.e., the occurrence of a branch instruction in the pipeline register operates to inhibit CLK 2 for one CLK 1 time so as to prevent loading for execution of the aborted sequential instruction during the loading of a new non- sequential instruction address. CLK 2 resumes upon the next CLK 1 signal to resume sequential operation. Special branch instructions are utilized to fetch macro-instructions from a pipelined system of macro-instruction registers. A two-tier synchronous arbitration system for memory requests is also disclosed.

John Thomas Gehmann

Papers

High-speed synchronous computer using pipelined registers and a two-level fixed priority circuit

Pipeline Control apparatus for generating Instructions in a Digital Computer