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Upgrading P4S55FX+ from 2GB to 4GB


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I have an ASROCK P4S55FX+ with 2GB installed (2 1GB modules). I wanted to

increase the amount of memory and purchased a Corsair 2GB Memory Module Kit (two

1GB modules), ValueSelect, VS2GBKIT400C3, each module is labeled VS1GB400C3. I

have not opened the package of new memory yet, and wanted to get a couple

questions answered before opening the package, so that I may return it if I need



The P4S55FX+ manual states the motherboard takes 3.5GB max memory. May I install

these additional two 1GB modules? Will the motherboard accept them, but only

address 3.5GB of the 4GB? (Is the other 0.5GB for addressing other things on

the motherboard?) Or, must I buy a kit with 2 0.5GB modules to go with the

existing 2 1GB modules?


If I can install all 4 1GB modules, how would I best configure my BIOS?

The already installed 2 1GB modules are matching and running

in dual channel mode. I cannot tell the make or model of the already-installed

2 1GB modules. Is it true that I can install the two new 1GB modules

into the remaining slots and still run the motherboard in dual channel mode?

(I know the existing 2 modules are in identically-colored slots and the two

new modules should be installed into the remaining 2 identically-colored slots.)


My BIOS currently has the following settings:


DRAM Access Mode: [Dual Channel]

DRAM CAS Latency: [Auto]

DRAM Precharge Time: [Auto]

DRAM RAS to CAS Delay: [Auto]

DRAM ACT to Precharge Delay: [Auto]

DIMM1, 2 Address/Command Rate: [2T]

DIMM3, 4 Address/Command Rate: [2T]

DIMM1, 2 FWDSDCLK Delay: [Auto]

DIMM3, 4 FWDSDCLK Delay: [Auto]

DDR IO Input Termination: [170 Ohms]


After installing the new Corsair memory, how should I set these settings?


Thank you very much for any help you can give.



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