Appeal No. 1997-4127 Page 2
Application No. 08/044,241
BACKGROUND
The invention at issue in this appeal relates to a system
read-only-memory (ROM) for a computer. A computer employs
different types of memory to store data and code. A system
ROM is a small, non-volatile memory used to store permanent
data and code that are used regularly by the computer. Among
the code stored is primary boot code. Because primary boot
code is needed to initialize the computer, it must neither be
lost nor changed. The remaining code in the system ROM is
subject to change as bugs or errors are discovered.
A boot block flash EPROM is often used as a system ROM.
The boot block flash EPROM includes two portions. A small
portion is used to store primary boot code; a large portion,
remaining boot code. Each portion has an erase-enable pin.
The pin of the small portion is disabled to prevent accidental
erasure. Boot block flash EPROMs, however, have been scarce.
Instead of a boot block EPROM, the invention uses two
memories, viz., a one-time programmable (OTP) ROM and a flash
EPROM, as a system ROM. The OTP ROM is used to store primary
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