HP Kayak XU800 Series, Technical Reference Manual

Page: 64 / 140

64
2 System Board
Host Bus
Host Bus
The Host bus of the Pentium III processors, also referred to as the FSB
(Front Side Bus), is implemented in the GTL (Gunning Transceiver Logic)+
technology. This technology features open-drain signal drivers that are
pulled-up to 1.5 V through resistors at bus extremities; these resistors also
act as bus terminators, and are integrated in the processor.
If only one processor is installed, a terminating board must be installed in
the second processor slot.
The supported operating frequencies of the GTL+ bus are 100 MHz or
133 MHz. The width of the data bus is 64 bits, while the width of the address
is 36 bits. Along with the operating frequencies, the processor voltage is set
automatically.
The control signals of the Host bus allow the implementation of a “split -
transaction” bus protocol. This allows the Pentium III processor to send its
request (for example, for the contents of a given memory address) and then
to release the bus, rather than waiting for the result, thereby allowing it to
I840
Memory
Controller Hub
(MCH)
82840-QP
Memory
Expansion Card
Connector
Dual Rambus Bus
Address (36)
Control
Data (64)
AGP 4x Bus
Intel Pentium III
Processor
(optional second processor)
with L2 cache memory
SECC-2 cartridge
SECC-2 cartridge
Host (also called FSB)
Bus 100/133 MHz,
1 GB/sec data trans-
fer rate)
HUB
LINK 16
HUB LINK 8
Intel Pentium III
Processor
with L2 cache memory
I/O Controller
Hub
(ICH) 82801AA