Intel 440GX ユーザーズマニュアル
Intel
®
440GX AGPset Design Guide
3-15
Design Checklist
3.6.2
DIMM Solution With FET Switches
•
With existing 64Mbit technology, 512 MB, 1 GB and 2 GB support for servers and
workstations must have 4 double sided DIMMs.
workstations must have 4 double sided DIMMs.
•
500 ohm - 1K ohm pull-down resistors on each of the second inputs (1A2, 2A2, etc.) are
recommended on the FET switches (500 ohms is recommended based on simulation) to
prevent a direct short to ground while switching.
recommended on the FET switches (500 ohms is recommended based on simulation) to
prevent a direct short to ground while switching.
•
All 72 DQ lines are fed through the FET switch.
•
The current FET switch is Pericom PI5C16212A, package type A56. See third-party vendor
list for more FET switch vendors.
list for more FET switch vendors.
•
12 functional units per part requires 6 devices on motherboard.
3.6.3
Registered SDRAM
•
There may be power and thermal considerations for registered DIMMs. If a design is going to
support registered DIMMs, the DIMM spacing may need to be evaluated based on mechanical
and cooling issues.
support registered DIMMs, the DIMM spacing may need to be evaluated based on mechanical
and cooling issues.
•
REGE, pin 147 on all the DIMMs needs a 0 ohm pull-up to enable registered DIMMs.
•
Data lines are directly connected to the SDRAM components, while all address and control
signals are registered. The clock signal is routed via a PLL to all the SDRAM devices.
signals are registered. The clock signal is routed via a PLL to all the SDRAM devices.
•
Access to registered DIMMs requires an additional clock of leadoff latency, programmable in
the 82443GX.
the 82443GX.
Figure 3-3. Current Solution With Existing FET Switches
8 2 4 4 3 G X
F E T
S W
R 0
R 7 1
D Q 0 - 7 1
D Q A 0 - 7 1
D Q B 0 - 7 1
D
I
M
M
M
0
FENA
D
I
M
M
M
4
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