Intel 440GX User Manual
Page 72
Intel
®
440GX AGPset Design Guide
3-12
Design Checklist
•
GTLREFx pins are driven from independent voltage dividers which set the GTLREFx pins to
VTT*2/3 using a 75 ohm and 150 ohm resistor ratio.
•
The 82443GX GTL_REF[B:A] pins should be adequately decoupled.
•
The 82443GX component is a 3.3V component. All pins labeled as VDD should be connected
to VCC
3.3
.
•
VDD_AGP pins have been changed to VDD pins.
•
The VSSA pin has been changed to VSS.
•
The 82443GX REFVCC5 pin can be connected to the same power sequencing circuit used by
the PIIX4E. See the PIIX4E section for further information on sharing this circuit.
•
The 82443GX AGPREF pin is required to be 0.4 of VCC
3.3
, this can be performed by a
voltage divider.
•
The 82443GX GX_PWROK can be connected to the PIIX4E PWROK pin.
•
The 22 ohm series resistors on GCLKOUT and GCLKIN should be placed next to the driver
GCLKOUT.
•
CRESET# is used to control the reset values of A20M#, IGNNE#, and LINT[1:0] and
determine the ratio of core and bus frequencies. This signal is delayed to provide the two
BCLK hold requirement. A 10K ohm pull-up to 3.3V is recommended.
•
TESTIN# should be pulled up to VCC
3.3
with an 8.2K ohm resistor. The internal pull-up may
prove to be sufficient, however the first rev of boards should include the external pull-up to be
safe.
3.5.2
82443GX GTL+ Bus Interface
•
The Intel
®
440GX AGPset does not support the entire Intel
®
Pentium
®
II processor GTL+
bus. For a UP design, on board termination resistors are recommended for the following
signals: HD[63:0]#, A[31:3]#, HREQ[4:0]#, RS[2:0]#, HTRDY#, BREQ[0]#, BNR#, BPRI#,
DBSY#, DEFER#, DRDY#, ADS#, HIT#, HITM#, HLOCK#, CPURST#. The second set of
terminations are provided on the Intel
®
Pentium
®
II processor.
•
The Intel
®
440GX AGPset does not support the entire Intel
®
Pentium
®
II processor GTL+
bus. For a DP design, on board termination resistors are NOT required for the following
signals: HD[63:0]#, A[31:3]#, HREQ[4:0]#, RS[2:0]#, HTRDY#, BREQ[0]#, BNR#, BPRI#,
DBSY#, DEFER#, DRDY#, ADS#, HIT#, HITM#, HLOCK#, CPURST#. The second set of
terminations are provided on the second Intel
®
Pentium
®
II processor or terminator card. An
empty Slot 1 connector is not allowed.
3.5.3
82443GX PCI Interface
•
If boundary scan is not supported on the motherboard: (See the PCI Specification Rev 2.1
Section 4.3.3 for more information)
TRDY#
2.7K ohm pull-up to 5V. Connected to PCI bus.
VTTA, VTTB
GTL threshold voltage for early clamps.
WE[B:A]#
Each connected to up to 2 DIMMs.
WSC#
UP: Leave as a NC. DP: Connected to IOAPIC. No pull-up resistor is needed.
Table 3-4. 82443GX Connectivity (Sheet 3 of 3)
SIGNAL
CONNECTION