have 4GB OCZ memory, and an MSI K8N Neo4 Platinum motherboard. When I use only the first two slots on the mainboard, for 2GB RAM, the BIOS detects the memory as DDR 400, which is correct. When I use all 4 slots, for 4GB RAM, the BIOS detects the RAM as DDR 333, which is incorrect. Also, the RAM is running at 200Mhz, when it should be running at 400Mhz. Why is the BIOS detecting and configuring the RAM incorrectly? Can you help me with this?

First ddr400 runs at 200mhz, 400mhz is the effective clock rate.

If you want you can set the ram speed and timings manually to match the specifications.

As the guy above said, the computer sometimes doesn't correctly set the memory speed right, set it manually in the BIOS.
One of the memory modules may not support the speed at those timings, try swapping one out at a time to check what the machine can run at.

Ripped from a previous post of mine:
--Snip---
Problems with 4 GiBs of system memory in PC's

Problem 1) The "Memory Hole" problem: because of legacy reasons, all device interface maps reside at the top of the 4GiB address space (the idea being allowing memory mapping of devices in standard memory space, start at the end (which, at the time was 2^32 bits, or 4GiB, and work backwards). This requires mapping of the memory that would be unaccessible due to overlaping these device maps to the address space above 4GiB. This can be accomplished in either software (via BIOS + OS awareness) or in hardware (via BIOS and hardware ability, only available in the 90nm chip revision

Problem 2) The "Hey, where'd my other 2 gigs go?" problem: Windows XP 32-bit (Home only comes as 32-bit) is able to address 32-bits worth of address space (without ugly hacks like PAE, but that's for another thread) which, as said before, is 4GiB. We're money, right? Unfortunately not, as Windows splits the address space and hence the memory into "kernel memory" and "user memory", and it splits this 4GiB address space right down the middle, leaving processes only able to access, at most, 2GiB of space. While there is no solution to make Windows let any process use all of the possible address space short of adding more address bits, there is a boot parameter you can set in boot.ini that may help the situation, /3GB, when appended to the boot params can allow processes the ability to use up to 3GiB of address space at the cost of the kernel only having 1 GiB. As such, I've seen this approach work wonders and I've seen this approach crash systems, requiring fine-tuning of the address split using the USERVA=##### switch to back off from 3GiB. Even after all of that, note that only certain applications that have been compiled with special flags will even be aware of the possiblity to use more that 2 GiB of memory, and most of those are in the scientific and engineering realm.

Problem 3) The "Where's the performance?" problem: As others have touched on here, save high-end video editing, veryhigh end photo editing, mathematic simulations on large data sets, running a mid level to entry-enterprise level (web|DB|domain)server, or any other application where routine access to large, large ammounts of data is the order of the day, you will see little to no improvement over 2GiB. There are many articles around (including one on THG) that illustrate this.

Problem 4) The "Windows x64 kinda sucks" problem: As stated before, the only "real" way to see all those pretty bytes is to get a system that has the kinda available address space to house that memory and the mapped devices in one go which requires an operating system that has a few extra address bits in it's addresses. What you will quickly realize is that some of your old hardware won't work anymore and, guess what? it never will. Many companies just aren't supporting 64-bit drivers and, while the situation is much improved from "the early days", it still is a problem. Even beyond that, you will have to install many 32-bit programs as there aren't 64-bit verions of them, and when there are (IE and Firefox), some plugins are not (Flash, Java plugin), which requires the 32 bit browser. Linux and BSD is much better in the driver realm, but that point is probably moot here. Thus is life on the bleeding edge.

Finally, I mean you could always upgrade later, I mean you can still buy pc133.
--Snip--

Filling all 4 DIMM's on a s939 board usually forces the memory to run at 333. That's a very common problem. The only way around it is to pull 2 sticks, and live with 2GB(recommended), or wait til 2gb sticks come out, and install 2(not recommended). Also, with the 4 DIMM's filled, the memory controller forces a command rate of 2. Just stick with 2 sticks, and it'll perform much better. GL

Thanks to everyone for replying. I contacted OCZ tech support and they gave me these settings to adjust in my BIOS:

High Performance Mode......................... Manual Aggressive Timing............................. Disabled Dynamic Overclocking.......................... Disabled Adjust CPU FSB Frequency...................... 200 HT Frequency.................................. 5x HT Width...................................... 16 16
CPU Spread Spectrum .......................... Disabled
SATA Spread Spectrum.......................... Disabled
PCI-E Spread Spectrum......................... Enable
PCI-E Clock................................... 100 MHz SSE/SSE2 Instructions......................... Enabled Cool 'N' Quiet................................ Disabled Adjust CPU Ratio.............................. startup / Auto Adjust CPU Vid................................ startup Extra CPU Voltage............................. By CPU VID Memory Voltage................................ 2.75V NF4 Voltage................................... 1.50V

DRAM Configuration

Timing Mode................................... Manual
Memclock Index Value (MHz).................... 200
CAS Latency (Tcl)............................. 2.5T
Min RAS# active time (Tras)................... 8T
RAS# to CAS# delay (Trcd)..................... 3T
Row precharge time (Trp)...................... 2T
Row to Row delay (Trrd)....................... 3T
Row Cycle time (Trc).......................... 12T
Row refresh cyc time (Trfc)................... 16T
Read to Write delay (Trwt).................... 3T
Write recovery time (Twr)..................... 3T
Write to Read delay (Twtr).................... Auto
Refresh Period (Tref)......................... 1x3120 Cycles User Config Mode.............................. Manual Bottom of 32-Bit[31:24] IO.................... D0 1T/2T Memory Timing........................... 2T Read Preamble Value........................... 6ns Async Latency Value........................... 6ns
S/W Memory Hole Remapping..................... ENABLED
H/W Memory Hole Remapping..................... ENABLED
MTRR Mapping Mode............................. Continuous


I did this and now everything runs as its supposed to. 4GB Ram detected, DDR 400. Hope this can help someone who has a similar problem. This however, did not resolve the problem mentioned above where Windows has a problem detecting all 4GB of RAM. I'm running WinXP Pro 32-Bit, an only 3GB are detected, but I can live with that.

One thing you can do, just to try things out, is download the Windows XP Pro x64 Trial, dig out an old, unused hdd and installing it dual-boot style. If you don't have a spare hdd, simply defrag your current disk, use you favorite partition tool (e.g. Partition Magic or, my fave, the GParted LiveCD) to resize the existing NTFS partition and install XP x64 into the newly freed space.

Just an option to test the waters to see if x64 works for you, your hardware, and your software needs.

BTW, I can guarantee you the memory timing relax (as stated by Kholonar and 1Tanker) and the remapping (as I pointed out earlier) is what made the memory visable to BIOS.

Otherwise, the real boon to compatibilty is going to have to wait for Vista x64.