Abstract: An emulation system emulates operation of a graphics processor in a target computer system that is executing a computer program. The graphics processor in the target computer system executes graphics commands generated by the program being executed to as to generate a sequence of frames that are to be displayed. The emulation method is performed by an emulation module that is executed by a general purpose computer. The emulation module receives a sequence of graphics commands and stores the graphics commands in a command cache. Upon detecting a frame end, the emulation module executes at least some of the commands in the command cache so as to at least partially render a frame represented by the commands in the command cache and thereby store image data in a video memory (VRAM). At each frame end the emulation module evaluates the ability of the general purpose computer to generate video frames fully synchronized with the target computer system.

Abstract: A temporal compression and decompression system is disclosed for color video. A video stream with red, green and blue pixel element values is input to a first computer. In the first computer, a new frame of video data is compared to the frame being displayed on a second computer and the similarity between corresponding blocks and sub-blocks is represented with one tolerance result per sub-block. Based on the number of sub-blocks for which tolerance results exceed a preset threshold and a user-specified quality level, an update quality level is selected that determines the quality at which the frame update is transmitted from the first computer to the second computer. Before the frame update is transmitted the updating information is compressed in a two-stage process. In the first stage 5-bit red, blue and green element values in sub-blocks being updated are is converted to 3-bit categories. In the second stage groups of categories are converted to variable-length Huffman words.

Abstract: In a computer system, a cross-compiler converts non-native code into native code immediately prior to execution of that code. The system also includes a code cache for storing cross-compiled code and a hash table for locating code blocks in the code cache. In a preferred embodiment, the system also includes an interpreter for emulating certain non-native instructions that are not converted into native code by the cross-compiler. While executing any non-native application, if the next instruction is not one of the predefined set of non-native instructions to be handled by interpretation or a special purpose procedure, then the next instruction is considered to be an "entry point" instruction, and the cross-compiler looks up the address of the entry point instruction in the hash table to see if a corresponding native code block is already stored in the code cache. If so, the native code block in the code cache is executed until an exit instruction in the native code block is encountered.

Abstract: A virtual memory system and method enable a computer system to use a virtual memory address space larger than the size of physical primary memory while swapping few, if any, pages out to secondary memory. Primary memory is divided into a work space, used for storing uncompressed pages in current use, and a "Compression Heap". A MappedOut storage space, which includes the Compression Heap and a portion of secondary memory, is used to store all pages swapped out of the work space. A virtual memory manager dynamically determines the number of pages of primary memory which need to be included in the work space, and moves pages of primary memory into the work space from the Compression Heap as needed. Pages are selected to be swapped out of the work space to the MappedOut storage space on the basis of memory usage data.

Abstract: A spatial compression and decompression system for color video data wherein a video stream is generated by a charge-coupled device with red, green and blue pixel elements. In a first compression stage, the 5-bit color data from each element is processed in turn. This step involves reading out from a lookup memory a 3-bit category (or compressed value) and 5-bit output value based on the 5-bit color data, a 5-bit previous value that represents same color data for a neighboring pixel and a 1-bit table select signal that determines in which of two similar tables the lookup is performed. The 3-bit category data for a pixel's three elements are combined and used as a 9-bit index into a Huffman table that performs the second stage of compression. Each Huffman table entry includes a variable-length Huffman code that represents more common categories with fewer bits, which provides additional compression over the first stage. The Huffman table reads out the code of the particular 9-bit category used for the lookup.

Abstract: A lossless data compression system and method compresses a set of M data words stored in a computer memory. A first table stores data representing last occurrence positions among those of the M data words already processed for all distinct word values. A second table stores for each data word an entry indicating the position, if any, of a most recent prior occurrence of another data word with the same word value. A dictionary index indicates how many distinct data word values have been encountered during processing of M data words.