User`s manual

4.4 Flash ROM (System ROM)
The address range for the higher bank is 3 FFF8 0000 to 3 FFFF FFFF, the
same as for the lower bank. Access is now to the higher bank and will continue
until the Alpha PCI 64–275 is reset or a 0 is written to the register at address
800.
Note
The update-enable jumper must be installed from pin J16-2 to pin
J16-3 to enable writing to the flash ROM. See connector J16 in
Table 2–3.
4–12 Functional Elements