Ray Yatman Cheng

US Patent:

58453253, Dec 1, 1998

Filed:

Apr 13, 1993

Appl. No.:

8/046476

Inventors:

William Van Loo - Palo Alto CA
John Watkins - Sunnyvale CA
Robert Garner - San Jose CA
William Joy - Palo Alto CA
Joseph Moran - Santa Clara CA
William Shannon - Los Altos CA
Ray Cheng - Cupertino CA

Assignee:

Sun Microsystems, Inc. - Mountain View CA

International Classification:

G06F 1516
G06F 1208

US Classification:

711135

Abstract:

Hardware and software improvements in workstations which utilize virtual addressing in multi-user operating systems with write back caches, including operating systems which allow each user to have multiple active processes. In virtual addressing, multi-user workstations, system performance may be improved significantly by including a virtual address write back cache as one of the system elements. Data protection and the reassignment of virtual addresses are supported within such a system as well. Multiple active processes, each with its own virtual address space, and an operating system shared by those processes in a manner which is invisible to user programs. Cache "Flush" logic is used to remove selected blocks from the virtual cache when virtual addresses are to be reassigned.

US Patent:

51192900, Jun 2, 1992

Filed:

Jul 16, 1990

Appl. No.:

7/554186

Inventors:

William V. Loo - Palo Alto CA
John Watkins - Sunnyvale CA
Joseph Moran - Santa Clara CA
William Shannon - Los Altos CA
Ray Cheng - Cupertino CA

Assignee:

Sun Microsystems, Inc. - Mountain View CA

International Classification:

G06F 1208

US Classification:

395400

Abstract:

Improvements in workstations which utilizes virtual addressing in multi-user operating systems with write back caches, including operating systems which allow each user to have multiple active processes directed to the support of alias addresses, i. e. , two or more virtual addresses which map to the same physical address in real memory Specifically, alias addresses are created so that their low order address bits are identical, modulo the size of the cache (as a minimum) for user programs which use alias addresses generated by the kernel, or wholely within the kernel. For alias addresses in the operating system, rather than user programs, which cannot be made to match in their low order address bits, their pages are assigned as "Don't Cache" pages in the memory management unit (MMU) employed by workstations which utilize virtual addressing.