AT&T 6300 Service Manual page 134

INSTALLATIONS
10. Verify a jumper is present on W17 and is not present on
W18 (Figure 3-32). A jumper on W17 defines the starting
address for the HDU Controller EPROM at C800:0000 and a
jumper on W18 enables the HDU Controller EPROM. The
HDU Controller EPROM must not be present.
11. Verify a jumper is present on W20 and not present on W19
(Figure 3-32). This sets the HDU sector size at 512 KB.
12. Locate the Drive Select Switch on the HDU Controller
(Figure 3-32).
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