In a graphic processing system, there are provided a main memory, a buffer containing a bit map memory for holding display data, a central processing unit for performing a data process involving a translation from a virtual address into a physical address so as to access the main memory, a graphic processor connected to the main memory and buffer, for processing data into a display form, and a system bus interface connected to the central processing unit, main memory and graphic processor, capable of exchanging the data among them. Furthermore, the graphic processing system includes a drawing processing unit connected to the system bus interface, for translating the virtual address into the physical address so as to access the main memory and to process the data, a bus arbitrator for performing arbitration between demands for using the interface given from the central processing unit and graphic processor, and a suspend circuit for asserting a signal requesting that the interface is released to the central processing unit.

Address-translatable graphic processor, data processor and drawing method with employment of the same

This invention implements a cache access system that shortens the address generation machine cycle of a digital computer, while simultaneously avoiding the synonym problem of logical addressing. The invention is based on the concept of predicting what the real address used in the cache memory will be, independent of the generation of the logical address. The prediction involves recalling the last real address used to access the cache memory for a particular instruction, and then using that real address to access the cache memory. Incorrect guesses are corrected and kept to a minimum through monitoring the history of instructions and real addresses called for in the computer. This allows the cache memory to retrieve the information faster than waiting for the virtual address to be generated and then translating the virtual address into a real address. The address generation machine cycle is faster because the delays associated with the adder of the virtual address generation means and the translation buffer are bypassed.

Translation look ahead based cache access

A translation of a portion of a virtual page number to a portion of a physical page number in a "TLB slice." The slice translation is used to index into a physical cache memory which has virtual tags in addition to physical tags and whose addresses are physical. By comparing the virtual tag to the input virtual address page number, it can be determined whether there was a hit or a miss in the combination of the TLB slice and the cache memory. By translating only a few bits of the virtual address to a few bits of a physical address, the speed of the device is greatly enhanced. This increased speed is achieved by making the TLB slice direct-mapped and by taking advantage of its small size to build it with special hardware (either high-speed RAM (random access memory) or with latches and multiplexers). There is no separate comparison at the TLB slice output for determining a TLB slice hit. The subsequent cache tag comparison is used to indicate both whether the translation was correct and whether there was a cache hit. To achieve this dual purpose comparison, however, a virtual tag must be combined with a physical cache to determine whether there is a hit, since the entire virtual address has not been translated and therefore there is no translated physical address to compare with a physical tag.

Two-level translation look-aside buffer using partial addresses for enhanced speed

A cache subsystem for a computer system which includes a cache memory and a cache control means. When the processor subsystem of the computer system requests data, information related to the location of the data within the memory subsystem of the computer system is input to the cache subsystem. The control means receives an address bus bit field and transmits control signals which vary depending on the received address bus bit field to the cache memory to look for the requested data. The address bus bit field is configured based upon the dimensions of the cache memory and includes information as to where the data would be stored within the cache memory. As different cache memories are of different dimensions, means for modifying the address bus bit field generated by the cache control means based on the dimensions of the cache memory are provided so that the cache subsystem may be readily configured to operate with different sized cache memories.

Computer system having a selectable cache subsystem

A computer graphics processor capable of reading from, and writing to, virtual memory The invention provides a graphics processing unit which includes, among other things, an graphic processor in the form of an address generator which retrieves data from memory locations, and writes data to memory locations The address generator retrieves data from memory locations memory access request directly to a memory control unit, which retrieves the contents of the memory location Prior to issuing the request, the address generator sends the address to a virtual translation unit, which translates the virtual address to a physical address The virtual translation/FIFO control unit also contains three translation buffers, in which are stored the most recently accessed virtual addresses, which, in many situations, enables the virtual translation/FIFO control unit to translate the virtual address using less memory accesses

Translation of virtual addresses in a computer graphics system

In a processor system with a virtual memory organization and a cache memory table storing the physical addresses corresponding to the most-recenty used virtual addresses, access to the cache table is enhanced by associating upper and lower MSB portions of a virtual address with corresponding upper and lower portions of an associated cache address. The separate cache address portions are placed in separate cache address storage devices. Each cache address storage device is addressed by respective virtual address MSB portions. A physical address storage device stores physical addresses translated from virtual addresses in storage locations addressed by cache addresses associated with the respective virtual addresses from which the physical addresses were translated.

Edward Harada

Papers

Cache memory address apparatus