My dad has a HP pavilion 510n at 1.2ghz pentium3 cpu. After checking it out I've determined it to have a Trigem "lomita" mobo. The system came with only 256mb ram (pc100 sdram).

According to HP, the mobo supports up to 512mb ram total. We couldn't find a 256mb pc100 sdram but the guy at the local computer shop said it should also take a 256mb pc133 sdram and run both at the slower speed (pc100), and it did detect the new ram, sort of.

The board won't detect the cheaper sdram dimm's (the kind with chips only on one side). As for the more expensive sdram dimms (the kind with chips on both sides), its doing something strange: its stating that the 256mb pc133 sdram is a 128mb pc133 sdram. (The sdram isn't mislabeled, and it isn't detected at the right size regardless of it being in the first or second slot and regardless of whether the 256mb pc100 sdram is in or not).

Does anyone know what might cause this error? The bios won't let me specifically state what size&speed the sdram is. (Is there a way to select that the sdram dimm's aren't auto-detected and instead manually select them from a preset list?)

Even stranger is that the system is now running MUCH FASTER than it was before. It still states on screen that its a 1.2ghz cpu, but booting/POST is like twice as fast and winXP is running like 30% faster. Its almost like as if instead of running both sdram's at the slower speed (pc100) its running both at 133mhz (which I've read can be forced but may cause all sorts of memory errors, but we had the system up for several hours with no problems).

matsho@sympatico.ca

Ouch, Trigem is the company that made eMachines. I think they actually owned the eMachines brand and sold it off to Gateway. So your HP is an eMachines...

You could make things easy on yourself and use Crucial's memory selector at their website to choose modules gauranteed to work with your motherboard. As for the problem you're having, blame the seller. It's likely a "density" issue, 99% of technicians don't even know what that means, the higher the density the cheaper it is to make, and the store would rather sell you dirt-cheap RAM that doesn't work than stock something a little more expensive that does work.

Thankfully we found a sdram that was detected correctly.

My dad took his computer to a new shop here in town and they went through nearly a dozen assorted new and used pc100 and pc133 sdrams until they found one that worked totally right. Not the kind of problem you'd expect for a pentium-3 that's not that old.

Apparently if you find the original Korean mobo manual its on-par in size and detail as most mobo manuals. Not that I'm saying bad things about Trigem or Korea (which is where Trigem is based).

HP though put it in several different machines, locking the bios different ways and in some cases doing strange things to the bios and/or mobo.

I am trying to find solid info on the board so I can tweak it and maybe even speed it up for my old man. Info on the web is scattered at best and downright conflicting if you try to use what's provided on the HP website.

Some people say that if you were unlucky enough to get a pavilion with the Trigem Lomita board that you should cut your losses and just buy a whole new mobo and cpu. A few say the Lomita mobo is crud. Yet others say upgrades are fully possible, but are completely dependant on what model pavilion you pulled the Lomita board from.

Here's a sample of my confusion:

Looking up the pavilion 510n with a Lomita on HP's site, it says if you put in a pc133 stick the bios should say it was pc133 of whatever size but you wouldn't see a speed increase since the mobo would still run it as pc100.
If on the other hand you have a 310n pavilion with Lomita mobo, you need to do a bios update in order to get the board to recognize pc133 sticks.
Strangeer yet, one the pavilion pages I saw with Lomita said it takes both pc100 and pc133 sticks, but runs all sticks as pc133. As far as I know, running a pc100 stick as a pc133 usually makes the system unstable unless you tweak other bios settings.

Or how about this:

If you look about, you'll see that they list this exact-same mobo in about a half dozen different pavilion machines. I know this mobo appears in the 310n, 311n, and 510n pavilion models, and possibly several others, and it has different stats and different "only this will work" type notes on every one.
Stranger yet, several of the pavilions that have Lomita mobo's state they need bios updates... yet there is only a single version of the "Lomita" board made by Trigem, and as such, there is only a single bios available.

Another example:
The 310n pavilion (1.1ghz) needs the bios update so it will recognize some or all pc133 sdrams. The 510n doesn't need the update. The 310n can take a faster cpu at 1.4ghz, but as best I can tell, the 510n cannot even though its the same Lomita board. And before you say its the bios, it isn't. The updated 310n pavilion bios is identical to the existing 510n bios (I checked it myself after downloading both from vastly different web sources), so as best I can guess HP physically must have removed and rewelded a jumper or resistor or something.

It sounds like everyone is guessing. There are good reasons for that!

HP has usually had problems with various types of RAM, even in their Asus boards. My standard practice for upgrading HP systems is to pull out a box of assorted used RAM and install every module until I find one that works.

Now, as for the board, it's probably using an i810E or i815E chipset under the Tualatin revision (that adds a letter to the chipset model number). Various boards might use older versions of the chipset! Worse still, some boards might support Tualatins while others don't! And Trigem, well, nobody says they have to document the hardware differences of each revision, so there could be several hardware revisions that you simply don't know about.

Now, the differences between the Tualatin and Non-Tualatin boards were SO MINOR that the same BIOS could be used for BOTH. In fact, most PIII boards that did not originally support the Tualatin processors (including your PIII 1.2)...would support them with the use of a simple adapter. It was found that the chipset revision Intel introduced was NOT NEEDED to support the Tualatin, the only thing that was actually needed was for a few pins to be re-wired on the socket! That opens up another possibility: Trigem may have re-wired the board to support YOUR processor WITHOUT using the revised chipset, WEEEEE!

At any rate, these chipsets supported split CPU/RAM speeds so that you could have a 133MHz FSB CPU running with RAM clocked at 100MHz, or even a 66MHz FSB CPU running with RAM clocked at 100MHz. But who knows what these companies did with their BIOS.

All these problems add up to one method to secure working RAM: Test everything and find something that works. Companies like Crucial have pre-tested their modules, found what works, and sell what works with a compatibility gaurantee.