Devices On The Processor-Local Bus; Intel Pentium Ii Microprocessor - HP Kayak XU Technical Reference Manual

NOTE

Devices on the Processor-Local Bus

The Processor-Local (PL) bus of the Pentium II processors, also referred to
as their FSB (Front Side Bus), is implemented in the GTL+ technology. This
technology features open-drain signal drivers that are pulled-up to 1.5 V
through 56 ohm resistors on both ends of the bus; these resistors also act as
bus terminators, and are integrated in the Pentium II processors. If only one
processor is installed, a terminating board must be installed in the second
processor slot.
A Pentium II processor may be inserted in either processor slot, but the
Voltage Regulator Module (VRM) must always be installed in the
corresponding slot (for example, if a Pentium II processor is installed in
processor slot 1, there must be a VRM in VRM slot 1).
The supported operating frequencies of the GTL+ bus are 60 MHz and
66 MHz. The width of the data bus is 64 bits, the width of the address is 32
bits.
The control signals of the PL bus allows the implementation of a "split -
transaction" bus protocol. This allows the Pentium II processor to send its
request (such as asking for the contents of a given memory address) and
then to release the bus, rather than waiting for the result, thereby allowing
to accept another request. The 440LX as target device then requests the bus
again when it is ready to respond, and sends the requested data packet. Up
to four transactions are allowed to be outstanding at any given time.

Intel Pentium II Microprocessor

The Pentium II processor has several high-performance features that
enhance performance:
• Dual Independent Bus architecture, which combines a dedicated 64-bit
L2 cache bus, plus a 64-bit system bus with ECC that enables multiple
simultaneous transactions (refer to above "split -transaction").
• Intel MMX technology, which gives higher performance for media,
communications and graphics applications.
• Dynamic execution to speed up software performance.
The Pentium II processor and level-2 cache memory are packaged in a self-
contained, pre-sealed module, installed in a socket on the system board. The
heat-sink is supplied with the processor, and is bolted to it by the
2 System Board
Devices on the Processor-Local Bus
15