Ive recently bought 2 x 1gb memory chips...

Hewlett-packard /
June 24, 2010 at 06:49:11
Specs: Windows XP, 2.40GHZ Pentium 4, 2X1GB + 1X 512mb
Ive recently bought 2 x 1gb PC4300 DDR2 Ram chips, they are compatabile with my machine and it boots up fine, however when I attempt to run programs like IE, Firefox, various games, they launch then crash after a short period, im currently running with the original 512mb chip that came in the machine and the 2 new chips, ive tried all sorts of slot / combinations and seems to have the same problem, my motherboard supports 4GB of memory over the 4 slots my machine is a HP Compaq DC5100...tried running crucialUKscan software and this picks up my memory with no problem....help please!!!

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June 24, 2010 at 07:26:39
You may have RAM that has specs that are too different to be compatible, or the RAM may be defective.

One common issue is modules may not require JEDEC standerd voltages but something usually higher. The module in the first slot is usually the stick that sets those parameters. The motherboard can't send different voltages to each RAM slot. All will receive the same.

OEM computers like Compaq can be fussy about the RAM they will run. If you remove the new RAM and go back to crucial.com and use their online scan feature it should tell you the preferred modules.

Also, download and run memtest 86 from a boot disk. Do not buy RAM from ebay.

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June 24, 2010 at 08:20:41
"...PC4300 DDR2 Ram chips...".

They're memory modules or ram modules, not chips.
Computer memory you install in slots in the mboard comes on modules - at least 4 individual memory chips are wired up on each module.

PC4300 ram runs slower (533mhz) and you are supposed to use PC5300 (667mhz) or PC6400 (800mhz) ram in this model's mboard.

Did you mean to say PC5300 ?

Your problem might be due to.....

- there is a poor connection of the memory modules in the ram slots.

Unplug the computer, or otherwise switch off the AC power to it, at ALL times when you're going to be fiddling with any memory module or card or wiring connection to the mboard, or wiring connection to the power supply.

Make sure the ram modules are all the way down in their slots, and that the latches at each end of the slot are against the ends of the modules.
Do not touch the contacts on the edge of the ram modules with your fingers before you plug them in.
Sometimes you need to remove the modules, wipe off the contacts with a tissue or soft cloth, and install them again, or you may need to try removing / installing them several times.

or - your original ram module(s) require(s) a different voltage than the two new ones.

The original ram module(s) and the new ones may require different voltages.
The standard JEDEC spec voltage for DDR ram is 1.8 volts. However, some memory modules require a higher voltage. Most mboards will automatically support using modules that require a higher voltage, but if you have a mix of modules that have different voltage requirements, the mboard's bios automatically sets the voltage for all the ram to the lowest voltage requirement. In that situation, you will have problems with the modules that require the higher voltage - not necessarily all the time, but certainly under some circumstances.
- try removing the original module(s) to see if your problem goes away.

Side notes - if all the ram is rated for the same voltage .....
Some ram manufacturer's modules do not strictly adhere to the JEDEC standards that most mboards bioses use to determine ram settings.
In that case, the ram settings in the bios Setup that the bios has automatically chosen may not be correct.
Check the ram settings in your bios - the ram voltage, and the ram timing numbers - those should be the same as for the specs for the modules themselves. Often the ram voltage and timing numbers are printed on the label on the modules.

If the voltage setting or timings settings in the bios are different from the specs for the ram, change them in the bios. The timing numbers must be as close as you can get to the same, or slower timings (higher numbers = slower) - you won't notice the difference the slower settings make.

You can use certain programs that can read the information about the module's requirements and ratings on the tiny SPD chip that contains that info that is on one end of the module. E.g. CPU-Z
Or, the new modules, possibly the original one(s), often have a label on them that specifies what voltage they are supposed to use.
Or, you can use the part number on the module to look up it's specs on the web, although some modules that come with brand name computers have oddball brand specific part numbers that yield you not enough or no information.

If the two 1 gb modules are a matched pair that can run in dual channel mode ( or if the modules are not a matched pair but have the identical part number and were bought at the same time they can usually run in dual channel mode)......

- in the real world, having all your ram running in dual channel mode results in only a tiny improvement in memory performance - a few percent at best.
- when you have three modules installed, all of the modules will be forced to run in single channel mode by the bios
- if you have a pair of identical modules, or two pairs of identical modules, each pair doesn't need to be the same mb capacity as the other, but each pair must be installed in specific ram slots in order for all the ram to run in dual channel mode.

Support for your model.

Business Support Center
HP Compaq dc5100 Microtower PC


Hardware reference guide

In that - See
Installing additional memory
Installing DIMMs

When you have a mix of modules installed, the mboard's bios usually uses the least of the specs of the modules for all the modules installed (see the Side notes above).

E.g. in addition to them possibly requiring a different voltage, if the original module(s) have other lower specs, all the ram will run at those specs when the original module(s) is(are) installed.
E.g. if the original module(s) have
- a lower PCxxxx rating than the new ones, all the ram will run at that lower PCxxxx rating. In this case, you will probably notice the performance difference in comparison to the two new modules when the original module(s) is(are) not installed.
- higher (slower) timing numbers, all the ram will run at those slower timings (however, the difference is hard to perceive).

If all the modules installed are rated to use the same voltage, and if there is no problem with the connection of the ram modules in their slots, the ram will pass a memory test.

If you want to try a memory diagnostic utility that takes a lot less time to run a full pass than memtest86 does, this one is pretty good - Microsoft's
Windows Memory Diagnostic:
It can be toggled (press T) to do a standard or a more comprehensive set of tests - use the default 6 test one first - if it passes one pass of that, use the latter one. A few of the tests in the latter set are intentionally slower.
If you don't have a floppy drive, see the Quick Start Information at that Microsoft link for how to make a bootable CD of the Windows Memory Diagnostic (you need Windiag.iso - you don't necessarily need to use the program they mention to add it to the CD).

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