Ram not detected

October 10, 2010 at 07:24:00
Specs: Windows XP
i am having pentium 4 processor. my motherboard has sd ram socket. when i insert a 256mb sd ram in it ,it shows inly 127 mb.i tried even by updating the bios and changing the ram timing. but there is no change. what to do?

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October 10, 2010 at 07:49:18
Use the correct memory, use the Memory Scanner Tool at


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October 10, 2010 at 08:47:48
Read this article, especially what's written in "Step 6":


How much total RAM do you have? Although the minimum for XP is 128MB, it really doesn't run well unless the RAM amount is 512MB or better.

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October 10, 2010 at 08:55:34
Tell us the make and model of your brand name system, or if you have a generic desktop system, the make and model of the mboard.

The specific model of a brand name system is shown on a label on the outside of the case somewhere, or it can often be determined by going to the brand name's web site and loading a program they have available.
For Dell computers, they have a Service Tag number - the specific model can be determined by using that on their site, or can often be determined there automatically by you downloading some software. The Service Tag number should be on a label on the outside of the case, probably on the bottom on a laptop, on the back on a desktop, and is often also shown in the bios Setup.

The model, sometimes the make, of a mboard in a generic desktop system is usually printed on the mboard's surface in obvious larger characters, often between the slots.

The model is often also displayed on a logo (graphical) screen early in the boot, but it's often not as specific as the specific model number.

Ram that works in another mboard , or any ram you buy or have lying around, may not work properly, or sometimes, not at all - even if it physically fits and is the right overall type (e.g. SDram, DDR, DDR2, etc.; PCxxxx, xxx mhz) for your mboard. In the worst cases of incompatibilty your mboard WILL NOT BOOT all the way with it installed, and the mboard may not even beep - the ram has to be compatible with the mboard's main chipset, or in the case of recent mboards, compatible with the memory controller built into the cpu.

See response 5 in this for some info about ram compatibility, and some places where you can find out what will work in your mboard for sure:
Correction to that:
Mushkin www.mushkin.com

Once you know which module ID strings (part numbers) work in your mboard, you can get them from anywhere you like that has ram with those ID strings.

If you have brand name ram, it is usually easy to look up whether it's ID string (part number) is in a list of compatible modules found by using your mboard or brand name system model number.
If the ram is generic, that may be difficult or impossible.

Mboards that use P4 cpus have been around for a long time.

Older mboards (e.g. made before 2002 or so) that use the original SDram are often limited to using 16 chip 256mb modules - 8 chips on both sides - they often recognize 8 chip 256mb SDram modules as having a 128mb capacity.
If that applies to your mboard model, new 16 chip 256mb SDram modules are hard to find these days, but you may be able to find used ones on the web.

"it shows inly 127 mb"

Some bioses subtract 1mb from the total amount of ram installed for the conventional memory amount that can't be used by the computer user, some don't. If the mboard has onboard video and you are using it (you have no video card in a mboard slot) , some bioses subtract whatever ram amount is being shared with the onboard video. Whatever total ram amount the bios reports is the same as what Windows reports in System Information as Physical Memory.

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October 12, 2010 at 03:31:04
i am having an 258 &128mb sd ram.each slot in my motherboard has a capacity of 1gb

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October 12, 2010 at 15:04:56
Tell us the make and model of your brand name system, or if you have a generic desktop system, the make and model of the mboard.

If you have brand name ram modules, tell us the part number printed on the label on the modules.

Did you get 127mb total ram reported for when the 128mb one was the only one installed, or when the 256mb module was the only one installed, or when both were installed ?

You haven't told us which P4 cpu you're using. P4 cpus have been around long enough such that the earliest ones used mboards the original SDram was used on, later ones are on mboards that use DDR, DDR-2, or DDR-3 SDram.

Saying you're trying to use SDram is not specific enough.

Most ram made since the late 90's is SDram (some older mboards use RIMM ram).

First there was the original SDram, then DDR SDram, then DDR-2 SDram, then DDR-3 SDram.
(For DDR, DDR-2, and DDR-3 ram, the term SDram is often omitted in descriptions. If someone knows what the difference is, them saying they have SDram most often refers to them having / using the original SDram. )
All of those modules are exactly the same physical length.
Each type uses a different ram voltage.
The original SDRam / ram slots have 168 contacts (half on each side); the others have more contacts.
I very much doubt your mboard uses the original SDram - if your mboard can actually use 1gb modules in each ram slot, if 1gb modules exist at all they're extremely rare.
The original SDram has two notches in the bottom contact edge, the other types have one notch. Each type has notches in different positions.
The ram modules must be inserted in the ram slots in the proper direction, such that the notch or notches line up with the bump or bumps in the bottom of the ram slot. (If ANY ram module is inserted backwards in a slot, that ram module and the circuits for the ram slot it is in are both FRIED INSTANTLY when you attempt to boot the computer, and neither will ever work again.)
The ram modules must be the proper type for the ram slot they're installed in, or they won't be recognized, and could be damaged.

On top of that, even if you have the right type of module in the right type of ram slot, in the right direction, not all modules you think should work are compatible with - will work properly in - your mboard.

E.g. DDR-2 6400 and up ram modules can require a ram voltage higher than the standard JEDEC ram voltage. The mboard can usually auto supply the higher voltage, but if you mix modules that different ram voltages are specified for, the mboard's bios will automatically use the lowest ram voltage, and the modules a higher voltage is specified for will likely NOT work properly.

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