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
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