Method and structure for improving display data bandwidth in a unified memory architecture system

• US 5,790,138 A
• Filed: 01/16/1996
• Issued: 08/04/1998
• Est. Priority Date: 01/16/1996
• Status: Expired due to Term

• Current Assignee: Mosys Incorporated (Peraso, Inc.)
• Original Assignee: Monolithic System Technology
• Inventors: Hsu, Fu-Chieh
• Primary Examiner(s): Tung, Kee M.
• Application Number:
  US08/587,379
• Time in Patent Office: 931 Days
• Field of Search: 395/501-503, 395/507-509, 395/512, 395/511, 395/519, 345/185, 345/189, 345/201, 345/501-503, 345/507-509, 345/512, 345/511, 345/519
• US Class Current: 345/542
• CPC Class Codes: G06F 15/17 using an input/output type connection, e.g. channel, I/O port
• CPC Class Codes: G09G 2360/123 using interleaving
• CPC Class Codes: G09G 2360/125 using unified memory architecture [UMA]
• CPC Class Codes: G09G 2360/126 The frame memory having additional data ports, not inclusive of standard details of the output serial port of a VRAM
• CPC Class Codes: G09G 2360/128 Frame memory using a Synchronous Dynamic RAM [SDRAM]
• CPC Class Codes: G09G 5/363 Graphics controllers
• CPC Class Codes: G09G 5/393 Arrangements for updating the contents of the bit-mapped memory
• CPC Class Codes: G09G 5/399 using two or more bit-mapped memories, the operations of which are switched in time, e.g. ping-pong buffers

Abstract

A computer unified memory architecture (UMA) system and method which includes a unified memory which is partitioned into a main memory and a main frame buffer memory, as well as a separate expansion frame buffer memory. Together, the main frame buffer memory and the expansion frame buffer memory form an entire frame buffer memory. The UMA system performs a display refresh operation by alternately accessing the main frame buffer memory and the expansion frame buffer memory. Because the display data bandwidth is split between the main frame buffer memory and the expansion frame buffer memory, the data bandwidth of the unified memory is effectively increased, thereby enabling higher system performance. The expansion frame buffer memory has a relatively small capacity, thereby retaining much of the cost benefit of a UMA system.

Claims

1. A unified memory architecture (UMA) system comprising:

an address/control bus;

a data bus;

a unified memory which is logically partitioned into a main memory and a main frame buffer memory;

a system controller coupled to the unified memory by the address/control bus;

a data path controller coupled to the unified memory by the data bus;

a graphics controller coupled to the address/control bus and the data bus, whereby the graphics controller is coupled to the system controller, the data path controller and the main memory;

an expansion bus; and

an expansion frame buffer memory coupled to the graphics controller by the expansion bus, wherein the expansion frame buffer memory is physically separate from the unified memory and wherein the main frame buffer memory and the expansion frame buffer memory form a frame buffer memory for the UMA system.

2. The system of claim 1, further comprising a display monitor coupled to the graphics controller, wherein the expansion frame buffer memory stores data used to refresh the display monitor.

3. The system of claim 2, wherein the main frame buffer memory stores data used to refresh the display monitor.

4. The system of claim 3, further comprising a display controller which alternately accesses the frame buffer memory and the expansion frame buffer memory to refresh the display monitor.

5. The system of claim 1, wherein the graphics controller and the expansion frame buffer memory are on the same integrated circuit chip.

6. The system of claim 1, wherein at least two of the graphics controller, the system controller and the data path controller are on the same integrated circuit chip.

7. The system of claim 1, wherein the graphics controller comprises a data buffer coupled to the data bus, wherein the data buffer temporarily stores data received from the data bus.

8. The system of claim 1, wherein the graphics controller comprises:

a display controller;

at least one processor;

a first internal bus coupled to the display controller, the data bus and the expansion frame buffer memory, whereby the first internal bus provides data paths between the display controller and the unified memory and between the display controller and the expansion frame buffer memory; and

a second internal bus coupled to the at least one processor, the data bus and the expansion frame buffer memory, whereby the second internal bus provides data paths between the at least one processor and the unified memory and between the at least one processor and the expansion frame buffer memory.

9. The system of claim 1, wherein the address/control bus comprises a line for transmitting a signal from the system controller to the graphics controller to indicate whether the system controller is addressing the unified memory or the expansion memory.

10. The system of claim 1, wherein the address/control bus comprises a line for transmitting a signal from the graphics controller to the system controller to prevent the system controller from accessing the expansion frame buffer memory.

11. A method of refreshing a video display comprising the steps of:

alternately reading data values from a main frame buffer memory and a physically separate expansion frame buffer memory by a graphics controller, thereby creating a stream of interleaved data values;

providing the stream of interleaved data values to a display controller; and

transmitting the stream of interleaved data values from the display controller to the video display, thereby refreshing the video display;

wherein the main frame buffer memory is part of a unified memory which is logically partitioned into a main memory and the main frame buffer memory and the expansion frame buffer memory is coupled to the graphics controller by an expansion bus.