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Appendix C Functional Description C-33
C.1.14.5 SCSI ID Selection
The motherboard host adapter is assigned the SCSI identification of 7 for both ports.
The two internal drives attached to the SCA-2 connectors have a SCSI identification
of 0 and 1, while the CD-ROM has an identification of 6.
C.1.15 ASICs
The system unit achieves a high level of integration through application-specific
intergrated circuits (ASICs). All ASICs are 1149.1 (JTAG) compliant. The following
ASICs are highlighted and are described in the following subsections:
■ K9+
■ Marvin
■ PCI-to-EBus/Ethernet controller (Cheerio)
■ UPA-to-PCI bridge (PSYCHO+)
■ Frame buffer controller (FBC)
■ Reset, interrupt, scan, and clock (RISC)
Also included in this section are brief discussions of the SuperIO component.
C.1.15.1 K9+
The K9+ ASIC is a buffered memory crossbar device that acts as the bridge between
the six system unit buses. The six system unit buses include two processor buses
(144 bits wide), a memory data bus (two busses, each 288 bits wide), a graphics bus,
and two I/O buses. The chip is bit-sliced such that 9 parts are required to implement
a full connection to the system.
The K9+ ASIC provides the following:
Note – Referred data formats are as follows: a byte is 8 bits, a halfword is 16 bits, a
word is 32 bits, and a doubleword is 64 bits.
■ Six-port crossbar
■ Decoupled memory port; loading and unloading of memory data can take place
in parallel with other operations
■ Burst transfers operate on a doubleword of data per slice
■ A total of eight two-entry first-in-first-out (FIFO) devices for read data storage
■ Power-up safe buses (tristated)