EP0208428A2
Expired / Lapsed
EP
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Direct input/output in a virtual memory system
Assignee: HP Inc
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Filing: 1986-06-12
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Granted: —
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Expires: 2006-06-12
Abstract
Abstract A virtual memory system is used to control access to I/O device address space in accordance with a preferred embodiment of the present invention. In a virtual memory system, access to pages within a processor's address space are assigned to each application program. Each I/O device is assigned two pages of address space. One page is considered to be privileged, and the other unprivileged. Each I/O device register is associated with an address in each of the two pages of its 1 ! 0 device address space. Address space is global. What is meant by global is that physical memory locations map to the same virtual memory space regardless of what process is running on the processor. Access codes accompanied by a write disable bit are used to control process access to various addresses.
Inventors
- 👤 Steven C. Boettner
- 👤 David V. James
- 👤 William R. Bryg
- 👤 Tso-Kai Liu
- 👤 Michael J. Mahon
- 👤 William S. Worley
- 👤 Terrence C. Miller
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 06:08
CPC Classifications
G; G06; G06F; G06F12/00; G06F12/02; G06F12/08; G06F12/14; G06F12/1458; G06F12/1466; G06F12/1475; G06F12/0223; G06F12/0292; G06F12/06; G06F12/0646; G06F12/0653; G06F2212/00; G06F2212/20; G06F2212/206
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
129 words
We claim: 1. A computing device comprising: processing means for executing a plurality of processes; timesharing means for enabling the plurality of processes to timeshare the processing means. local memory means for storing data, the local memory means including a first plurality of physical storage locations; remote memory means for storing additional data, the remote memory means including a second plurality of physical storage locations; and, mapping means for assigning a virtual address to each physical storage location in the local memory means and in the remote memory means accessed by any process in the plurality of processes, wherein .the virtual address for each physical storage location in the local memory means and in the remote memory means is the same for each process in the plurality of processes.
Claim 2
Dependent Claim
27 words
A computing device as in claim 1 wherein the virtual addresses are grouped into pages, each page of virtual addresses having associated with it an access code.
Claim 3
Dependent Claim
72 words
A computing device as in claim 2 wherein each process has associated with it a plurality of access codes and wherein the processing means will not allow a first process having a first plurality of access codes to access a first virtual address in a first page, the first page having a first access code, unless the first access code matches a second access code within the first plurality of access codes.
Claim 4
Dependent Claim
31 words
4 . A computing device as in claim 3 additionally comprising a write disable means associated with the first process for preventing the first process from writing to the first page..
Claim 5
Dependent Claim
39 words
5 . A computing device as in claim 3 wherein a first virtual address within the first page is assigned to a first physical storage location, the first physical storage location being a control register of an input/output device.
Claim 6
Dependent Claim
25 words
A computing device as in claim 5 wherein a second virtual address within a second page is also assigned to the first physical storage location.
Claim 7
Dependent Claim
33 words
A computing device as in claim 6 wherein the first process may read the contents of the first physical storage location but may not change the contents of the first physical storage location.
Claim 8
Dependent Claim
31 words
8 . A computing device as in claim 6 wherein the first process has associated it a write disable means for preventing the first process from writing to the first page.
Claim 9
Dependent Claim
72 words
9 . A virtual memory system in a computer, the virtual memory system comprising: paging means for dividing virtual memory addresses within the memory system into pages; access means for allowing a first process running on the computer access to a first page of virtual memory addresses; and, disable means for preventing the first process from changing the contents of physical storage locations addressed by virtual memory addresses in the first page.
Claim 10
Dependent Claim
40 words
1 0. A virtual memory system as in claim 9 additionally comprising: means for mapping an I/O device register into a first virtual memory address in a first page, and into a second virtual memory address in a second page.
Claim 11
Dependent Claim
50 words
11 . A virtual memory system as in claim 10 wherein the first virtual memory address is at a first offset in the first page, the second virtual memory address is at a second offset in the second page and the first offset is the same as the second offset.
Claim 12
Dependent Claim
90 words
A computing system comprising: a peripheral device, the peripheral device comprises a first register; a memory management system, the memory management system comprising: an address space divided into a plurality of pages, a first page from the plurality of pages having a first plurality of addresses and a second page from the plurality of pages having a second plurality of addresses; access means for controlling process access to the plurality of pages; and, mapping means for associating a first address from the first plurality of addresses with the first register.
Claim 13
Dependent Claim
25 words
A computing system as in claim 12 wherein the mapping means associates a second address from the second plurality of pages with the first register.
Claim 14
Dependent Claim
20 words
A computing system as in claim 13 wherein the access means allows a first process access to the first page.
Claim 15
Dependent Claim
20 words
A computing system as in claim 14 wherein the access means denies the first process access to the second page.
Claim 16
Dependent Claim
34 words
1 6 . A computing system as in claim 15 wherein the first process is able to read data from the first register, but is not able to write data to the first register.
Claim 17
Dependent Claim
38 words
A computing system as in claim 15 wherein when the first process reads data from the first register, the act of reading data returns information to the first process, but has no other affect on the peripheral device.
Claim 18
Dependent Claim
24 words
A computing system as in claim 12 wherein a third address from the first plurality of addresses is associated with no physical memory location.
Claim 19
Dependent Claim
24 words
A computing system as in claim 18 wherein the first process affects no physical memory location by performing a write to the third address.
Claim 20
Dependent Claim
39 words
A computing system as in claim 18 wherein when the first process performs a write to the third address, the computing system writes data into a physical location associated with a fourth address from the first plurality of addresses.
References Cited (Backward Citations)
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