This enables the Zorro III Early Byte-Lane option, which results in an
overall speed increase of about 10% on the A4091.
From the Zorro III Bus Timing Addendum
2.4 Early Byte-Lane Option
There is now an optional early byte lane mode for full cycles. A bus
master can, optionally, drive /DS3-/DS0 according to normal address time
signal timing. Slaves that don't support this mode see /DSN at the
normal data-time, qualified by DOE. Slaves that do support this mode can
latch /DSN on the falling edge of /FCS. If at least one strobe is valid,
the slave gets a valid early byte-lane enable, and may use /DSn during
data time for write data latching. If none are valid, it will be
necessary to use /DSn at data time for sizing information.
This enables the Zorro III Early Byte-Lane option, which results in an overall speed increase of about 10% on the A4091.
From the Zorro III Bus Timing Addendum
2.4 Early Byte-Lane Option
There is now an optional early byte lane mode for full cycles. A bus master can, optionally, drive /DS3-/DS0 according to normal address time signal timing. Slaves that don't support this mode see /DSN at the normal data-time, qualified by DOE. Slaves that do support this mode can latch /DSN on the falling edge of /FCS. If at least one strobe is valid, the slave gets a valid early byte-lane enable, and may use /DSn during data time for write data latching. If none are valid, it will be necessary to use /DSn at data time for sizing information.
Found by dorken @ a1k