Electrical computers and digital processing systems: memory – Storage accessing and control – Hierarchical memories
Patent
1997-02-19
1999-05-18
Sheikh, Ayaz R.
Electrical computers and digital processing systems: memory
Storage accessing and control
Hierarchical memories
395309, 395733, 39518222, 395741, 395833, 711 1, 711114, G06F9/00;9/40;9/44;9/46
Patent
active
059058889
ABSTRACT:
An external hard disk is connected to a personal computer (PC) through the parallel port. A parallel-port expansion card is installed on the AT bus in the PC for communicating with the external hard disk. The parallel-port expansion card has a ROM containing intercept code. The address of the ROM is automatically configured when the system BIOS scans for expansion ROMs during booting. When no other ROM drives the data bus when an address is scanned, the parallel-port card latches the address and has the ROM drive its data onto the bus. Future accesses to the latched address access the ROM. The ROM's code replaces the interrupt table's starting address of the hard-disk-controller routine with the address of an intercept routine. All hard-disk operations using the interrupt first execute the intercept routine. The intercept routine copies any data writes to the external disk. Thus the external disk has a redundant copy of the PC's internal hard disk. The external hard disk can be the boot disk by having the intercept routine route all disk reads and writes to the external disk any not pass any disk operations through to the PC's internal hard disk.
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Jones Larry Lawson
Mambakkam Sreenath
Venkidu Arockiyaswamy
Auvinen Stuart T.
On Spec Electronic, Inc.
Sheikh Ayaz R.
Vo Tim T.
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