Chapter 4 PA-RISC Computer Systems - OpenPA.net

PA-RISC Chipsets Wax
(b) Two independent memory buses
(c) I/O channels (I/O ropes)
Pluto also contains memory and cache controllers. Part of the memory subsystems are sometimes
the zx1 SMEs (scalable memory expanders) that increase memory capacity and data rate (through
multplexing)
2. Mercury zx1 I/O adapters (IOAs) connect PCI-X/AGP slots and I/O devices to Pluto
The rest of the I/O chipset is made up of standard third-party I/O parts, such as SCSI controllers,
Ethernet devices etc.
Used in
� rp3410, rp3440, rp4410, rp4440, rp7420
� rx1600, rx1620, rx2600, rx2620, rx2660 rx3600, rx5670, rx6600, rx7620, rx7640, rx8620,
rx8640
� Superdome
� zx2000, zx6000
2.5.7 Wax
Wax is a secondary I/O controller complimentary to the LASI chipset. It implements various secondary
I/O functions and acts as a I/O bus to GSC adapter for different external buses as EISA, HP-HIL and
HP-IB. Most systems use it to complement LASI with other required I/O functions that were previously
implented in diverse I/O ASICs. It is implemented in the same process and package as LASI.
Features
� GSC bus interface with GSC+ features
� EISA bus converter
– Interfaces GSC to the 32-bit EISA, so EISA devices can attach
– Does not provide complete EISA bus conversion — provides an “Intel i486-like” bus interface,
to which external EISA chips attach
– Interfaces to external EISA controller: TI TACT84500 (provides EISA bus control unit
EBCU and EISA peripheral control unit EPCU
– Integrates the EDPU (EISA data path unit) functionality on-chip
– Attaches to i486 bus for control, bus and IRQ, and directly to EISA for data
– Can be switched at power up to operate as ISA controller (to directly interface with ISA-only
devices such as Token Ring controllers etc.)
� Serial interface — NS16550A compatible RS232 (software-compatible with LASI circuitry)
� HP-HIL interface, compatible to previously separate HP HIL chip (1820-4784) used in older
workstations
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