Gecko System Connect (Gsc); Processor Dependent Code (Pdc) And Stable Storage; Nio Bus Converter; Hewlett-Packard Precision Bus (Hp-Pb) - HP 3000 Series Handbook

For HP Internal Use Only
Gecko System Connect (GSC)
The MIOC provides the interface to the system main bus, which is the Gecko System Connect
( GSC). Gecko was the system for which this bus was originally designed. MIOC handles a
speed reduction of 2:1 from the CPU to GSC. In other words, the GSC runs at half the speed
of the CPU. The GSC provides the communication medium for the CPU, the GSC-to-NIO
Bus Converter, and the I/0 Interface (LAN, Stable Storage, etc). The GSC is made up of 32
address/data lines and associated control/handshake lines. The I/0 interface chip (LASI)
handles arbitration of the bus.
1/0 Interface
The I/0 Interface chip provides the LAN connection on HP 9000 systems. It contains
the Real Time Clock (RTC) and the interface to the Processor Dependent Code (PDC)
and Stable Storage firmware devices. This chip also handles the arbitration of the GSC
bus between itself, the Bus Converter, and the CPU. The LAN connection is via either a
direct AUI port or a 10-base-T MAU connection on the rear of the system card. The chip
automatically selects the port that has been connected to an active LAN medium. The real
time clock (RTC) circuit is made up of an internal counting register, an external oscillator,
and an external battery. The battery powers all three of these components when the system is
powered down.
Processor Dependent Code (PDC) and Stable Storage
The Processor Dependent Code (PDC) is stored in a downloadable flash EPROM on the CPU
card. PDC contains the system self-test routines, offline user interface, and numerous low level
routines that can be called from the operating system to return system information and to
handle certain error conditions (HPMCs ). This firmware can be updated to a new version
with an update program and an image of the new code, all supplied on tape or CD-ROM
media if an update is needed. The Stable Storage area is provided on a EEPROM and also on
the CPU card. Stable Storage contains certain system configuration parameters, such at the
primary and alternate boot paths, and other information such as a log of any previous HPMC.
Both parts are addressed and controlled through the I/0 Interface chip on the System card.
NIO Bus Converter
The NIO Bus Converter provides bus translation from the high speed GSC bus to the HP-PB
I/0 bus. Bus transactions are converted from the GSC protocol to the HP-PB protocol and
vice versa. In addition, the Bus Converter provides the interface to the Access Port, Front
Panel Status Display, and Chassis Status Display.
Hewlett-Packard Precision Bus (HP-PB)
The Hewlett-Packard Precision Bus (HP-PB) provides the interconnection and communication
mechanism for I/0 modules. Note that no memory modules are supported on the HP-PB
in these systems. The HP-PB is a 32-bit address/data bus with synchronous operation at 8
MHz. In these systems, slots 9 and 10 (2-slot systems), and 11 and 12 ( 4-slot systems) are
available for added I/0 interface cards. The Multifunction I/0 interface card resides in slots
13 and 14 and the HP-PB Bus Converter, for control purposes, occupies logical slot 15. Refer
to the block diagram for appropriate path addressing.
Functional Description 9-3