In the early versions of the 8813, the PROM at 0000h was the
standard 4.0 Poly monitor and the two PROMs at 0400h and 0800h
were the disk PROMs. Disk PROMs ver 7.5 are an example of this
configuration. With the introduction of the double-density con-
troller, additional code space was required so unused features
like tape support were removed from the 4.0 monitor PROM and
code for the DD FDC inserted into holes in the monitor PROM.
The ver 8.2 PROMs are an example of this later configuration.