3 Device AGP MotherBoard Design
3-24
Intel740™ Graphics Accelerator Design Guide
USB Headers P-20
This page shows the USB Headers. Note, the voltage divider on the open circuit signals provides
logic level transitions for the PIIX4E. Note the placement requirements for the capacitors and
series resistors at the bottom left.
Flash BIOS Component P-21
This page shows the 28F002BC-T Flash BIOS component which provides 128K bytes of BIOS
memory. A jumper is used to provide the option for allowing the BIOS to be programmed in the
system for BIOS upgrades and/or for programming plug and play information into the Flash
device.
Note that a 2Meg Flash device may be required for certain applications (motherboard devices such
as graphics, SCSI or LAN). An optional 34 pin header has been added to allow for BIOS
emulation.
Parallel Port/ Serial and Floppy/ Keyboard & Mouse P-23-25
Nothing new here.
VRM P-25
The top of this page shows the voltage regulator modules (VRM 8.2) connector(s). The VRM 8.2
module provides 5V to VCCcore voltage conversion for the Pentium II processor. The bottom of
this page shows two voltage regulators, one for generating the 1.5V GTL+ terminating voltage
(V
TT
), the other is a 2.5V regulator. The V
TT
generation circuit must be able to provide about 5.0
amps of current under worst case conditions.
Note that the 5.0 amps of current will normally be supplied from two linear regulator devices
(about 2.5 amps each), one located at each end of the GTL+ bus traces. However, one linear
regulator device (such as the LT1585A-1.5 supplying the entire 5.0 amps) can be used if both ends
of the GTL+ bus traces are near each other. For dual processors, two LT1587-1.5s (@ 3A) are
recommended.
Power Connectors Front Panel Jumpers P-26
This page shows the system ATX power connector, hardware reset logic, and standard chassis
connectors for the hard disk, power LEDs, and speaker output. New to this page are the dual-color
LED circuit required to indicate the system state (either ON, OFF, or any of the suspend states), the
6-pin optional ATX connector, and the Wake-On-LAN header.
Note: A CPU Fan Header is required for the Intel Boxed Pentium II processor. The dual-color LED
circuit is also used to reduce the voltage going to the power supply fan, thus decreasing its speed
and quieting the system.
GTL+ Bus Termination Resistors P-27
This page shows the GTL+ bus termination resistors. The components shown are flat chip resistor
array devices. These components are available in both four and eight resistors per package options.
These packages have been chosen for their small size to reduce board space required. Discrete, SIP
or SOJ resistor packages can also be used but will require more board area. Resistor packs with a
corner power pin are not recommended. A decoupling cap per resistor pack is also recommended.
Each GTL+ signal that connects between the 82443BX and the Slot 1 must be dual terminated to
insure proper GTL+ signaling. Each GTL+ signal should be routed using a daisy chain
methodology as described in the GTL+ layout guidelines section of this document. The termination
resistors for each net must be located at the ends of the nets. Connect the V
TT
side of the resistor
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