Sun Microsystems Sun Blade 1000 Service Manual page 291

The internal interface between the Sun CrossBar Interconnect interface block and the
leaf blocks is fully asynchronous. This allows the frequency of Sun CrossBar
Interconnect and UPA64S to be tuned according to the limitations of the system.
There is no relative frequency limitation, and the frequency of a leaf can be higher
than the Sun CrossBar Interconnect frequency.
UPA64S Leaf Block
The UPA64S leaf supports a slave-only UPA (UltraSPARC Port Architecture) bus
segment that supports two slave graphics devices. The SBC receives PIOs
(programmed I/Os) from the Sun CrossBar Interconnect and issues them onto the
UPA64S bus. The data is routed from the CPMS to the Sun CrossBar Interconnect
interface block, and finally to the UPA64S bus through the UPA leaf.
The UPA64S leaf is designed to sustain a stream of write PIOs at 120 MHz. This
translates to a sustained bandwidth of 800 MByte/sec.
The Sun Blade 1000 and Sun Blade 2000 workstations support a separate clock
synthesizer for the UPA64S bus, which is clocked at 120 MHz. See Section C.1.7,
"UPA" on page C-27 for details.
EPCI A Leaf Block
The extended PCI (EPCI) is the 64-bit, 66 MHz PCI. The PCI A leaf is the host
controller for the EPCI. It supports 3.3 V signalling only.
The PCI A leaf can support four master devices. The Sun Blade 1000 and Sun Blade
2000 workstation only includes only two master devices: the EPCI slot and the FC-
AL disk controller.
The microarchitecture of both PCI leaves is almost identical. The PCI A leaf also
supports the logic blocks mentioned above to comply with the Sun4u/Sun5
architecture.
The EPCI high-bandwidth pluggable I/O interface sustains up to 500 MBps in
streaming DVMA mode. See Section C.1.8, "PCI Bus" on page C-27 for details.
PCI B Leaf Block
The term PCI refers to the 33 MHz PCI bus (PCI specification revision 2.1). The PCI
B leaf is the host controller for the 64-bit wide/33 MHz PCI bus. It supports both 5 V
and 3.3 V signalling, and 32-bit devices.
Appendix C Functional Description C-19