An integrated semiconductor memory chip includes hardwired presence detect
data which can be accessed for transmission to a location external to the
memory chip as well as logic allowing additional presence detect data to
be programmed in the memory chip after fabrication of the memory chip.
Storing the presence detect data on the memory chip rather than on a
separate integrated circuit can help reduce the number of integrated
chips required for a memory module, which may include multiple DRAM or
other memory chips. Hardwiring at least some of the presence detect data
during fabrication of the chip can reduce the number of programming
errors as well as the number of mismatches that might otherwise occur if
a separate presence detect data chip were used. On the other hand, the
capability of programming presence detect data after fabrication of the
memory chip provides additional flexibility, allowing the foregoing
techniques to be used with a wide variety of memory chips and modules.