The 8049 has 2 kB of masked ROM as well as 128 bytes of RAM and 27 I / O ports.
2.
The memory module used " Masked ROM " ( MROM ), a type of memory chip that was not modifiable after manufacture.
3.
The particular variant chosen also had 4KiB of masked ROM on-chip, so an external ROM was not needed on the board.
4.
Masked ROM and fuse / antifuse PROM do not suffer from this effect, as their data retention depends on physical rather than electrical permanence of the integrated circuit, although fuse re-growth was once a problem in some systems.
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