Specifications

Futurebus+ Bus Support
15.11 Futurebus+ on DEC 4000
Figure 15–8 DEC 4000 Futurebus+ Address Space
ZK−6733A−GE
2 GB
CSR
space
Max
size
2 GB
Futurebus+ A32 Space DEC 4000 System Memory
0000 0000
7FFF FFFF
0000 0000
7FFF FFFF
8000 0000
EFFF FFFF
F000 0000
FFFF FFFF
The DEC 4000 I/O module responds as a Futurebus+ slave to A32 addresses in
the range 0000 0000 to 7FFF FFFF. A32 transfers in this address range will be
passed to system memory by the I/O module. Since the maximum size of DEC
4000 system memory is 2 GB (31 address bits), a Futurebus+ A32 address has
enough bits to access the entire DEC 4000 system memory.
If a Futurebus+ adapter requires Futurebus+ A32 space (in addition to its Initial
Node Space), the driver must call IOC$RESERVE_FBUS_A32 to reserve a region
of A32 space. On DEC 4000, IOC$RESERVE_FBUS_A32 will allocate 16 MB
pieces of address space in the region from A32 address 8000 0000 through EFFF
FFFF.
If the adapter requires Futurebus+ A64 space, the driver must call
IOC$RESERVE_FBUS_A64 to reserve a region of A64 space. Since the DEC
4000 I/O module does not respond to A64 addresses, the entire A64 address space
is available to adapters.
15.11.3 DEC 4000 ADP List
During booting, INI$IOMAP creates an ADP list that describes the DEC 4000 I/O
subsystem. The DEC 4000 ADP list appears as shown in Figure 15–9.
15–13