Data processor having bios packing compression/decompression architecture

Abstract

To increase the effective capacity of BIOS, an initial portion of the power on system reset (POST) code that is required to enable the system memory is stored in ROM in uncompressed form, and substantially the remaining portion of the BIOS code is stored in compressed form. Upon system initialization during a cold boot, the uncompressed portion of POST is executed from the ROM to enable the system memory, and then an image of the BIOS code is written to shadow memory. As BIOS code is needed during the remainder of the boot, the code is selectively decompressed from the shadow memory to another region of the system memory to which control is transferred. Variations based upon different boot scenarios are described.

Description

BACKGROUND OF THE INVENTION[0001] 1. Field of the Invention[0002] This invention relates generally to data processing, and more particularly, to storage and execution of BIOS code in a personal computer.[0003] 2. Description of Related Art[0004] All computers, such as the various models of personal computers, or PC's, produced by IBM, execute "operating system software" that instructs the PC on how to use other programs, termed "application software," such as word processing and spreadsheet programs.[0005] Examples of PC operating systems include MS-DOS and WINDOWS, manufactured by Microsoft Corporation, and IBM's OS / 2.[0006] Before a PC can run an operating system, it must load the operating system from a disk to the PC's working memory which is ordinarily random access semiconductor memory (RAM). This is carried out through a process known as "bootstrapping," or more simply, "booting" the PC. Booting occurs automatically when the PC is first turned on, a process called a "cold boo...

AI Technical Summary

Benefits of technology

[0020] An advantage of the invention is in overcoming the foregoing BIOS limitations while maintaining compatibility with existing PC architecture. Another advantage is in reducing the time required for bootstrapping. A further advantage is in performing BIOS code decompression under different boot sceneries, cold and warm, and upon memory conditions of real and protect.

[0021] The invention provides a data processing system comprising a central processing unit (CPU), a system memory for storing data in the form of electrical signals, a first port for receiving an input device generating electrical input signals, and at least one second port for supplying electrical output signals to output devices. The CPU is of a type including a BIOS circuit for carrying out prescribed functions including converting operating signals developed by an operating system executed by the CPU into electrical signals compatible with devices that are responsive to signals provided by the CPU to the system bus. In accordance with an important aspect of the invention, an initial portion of the BIOS code that is required to enable the system memory is in uncompressed form and a remaining portion thereof for carrying out prescribed functions including converting operating signals developed by an operating system executed by the CPU into electrical signals compatible with devices that are responsive to signals provided by the CPU to the system bus, is in compressed form.

[0022] In accordance with an aspect of the invention, the portion of the BIOS code that is uncompressed in ROM includes an initial portion of a power on system test (POST) code which is sufficient to enable the system memory, a remaining portion of which is compressed.

[0023] To reduce the time required for decompression of BIOS code, the code is transferred from ROM to the system memory in compressed form. Then, after a jump from one location of the system memory to another, decompression of the code takes place.

[0024] Upon cold boot, the initial portion POST is read directly from ROM to enable the system memory, and then an image of the entire BIOS code, the major portion of which is in compressed form, is written to RAM in the system memory, and control is transferred to the image. As needed, portions of the BIOS code including POST, Setup (if invoked) and then other BIOS routines are selectively decompressed from the shadow memory to another location of the system memory. Normal execution of POST and BIOS then proceeds until the boot is completed.

[0025] Upon a warm boot call, when the processor is in real mode, that is conventional with respect to INTEL 8088 type microprocessors, the procedure is similar but requires a solution to a complication, namely, that whereas the uncompressed POST code in ROM must be executed, the decompressed BIOS is currently mapped into the upper region of the system memory reserved for BIOS (000F0000h-000FFFFFh). Hence, in accordance with a particular aspect of the invention, ROM mapping is modified by carrying out a memory swapping process as follows. System BIOS restarts the system by transferring control to the region of the BIOS image corresponding to power up (000FFFF0h) in shadow RAM. Then, control is transferred to a region lower in the shadow RAM image (000E0000h-000EFFFFFh). The upper region of the image (000F0000h-000FFFFFh) is remapped from shadow RAM to ROM, and control is transferred to that region (in ROM).

Problems solved by technology

In the absence of these files, the BIOS will generate an error message.

However, the size of the portion of the read only memory (ROM) resident in a PC for storing BIOS code is limited.

In view of the 128K boundary defined for BIOS, the existing BIOS ROM is insufficient in size to accommodate the necessary services (features and functions).

However, paging and other approaches that require an ROM memory of increased size are accompanied by additional hardware requirements, and hence, cost, and in some cases, system performance degradation.

These attempts have been limited, however, to compressing only the SETUP and, more recently, the video BIOS area.

But the remaining portions of the BIOS code have not been a candidate for compression, among other reasons because there has been no mechanism for compressing large blocks of BIOS including the POST component of the BIOS code, decompressing and then booting successfully.

More particularly, a problem is encountered when considering how to compress and thereafter decompress BIOS code upon system initialization.

Furthermore, decompression of BIOS from the ROM into the shadow memory is relatively slow, increasing the time required for bootstrapping.

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