Instruction manual

A.6.1 Performing Read and Write Operations
You can perform block-mode write operations through the TURBOchannel bus
only in dense I/O space.
When you write to a number of I/O registers, the CPU attempts to gather them
in 32-byte blocks, unless you instruct it otherwise with barrier instructions.
Table 77 lists the effects of writing these chunks of data to the TURBOchannel
interface.
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Table 77 Writing 32-Byte Blocks to the TURBOchannel Interface
Space
Block-Mode
I/O Write Effect
Dense Enabled for
that slot
CPU collects as many longwords as possible into one
block-mode I/O write. The byte masks supplied to the
TURBOchannel must all be zeros.
Dense Disabled CPU writes data longword by longword. The byte masks
supplied to the TURBOchannel must all be zeros.
Sparse NA CPU writes data longword by longword using the byte masks
that you specify.
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The logic starts at the low longword of each chunk and moves toward higher addresses.
Write logic resolves conflicts, which are hidden from the the programmer.
A–6 Dense and Sparse Space