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RAM limitations of motherboards


Tommy

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Since I really like dealing with older machines, there's something really itching on my mind. Why are so many systems that use PC1xx SDRAM limited to 512MBs of RAM? Since PC133 512MBs exists, why can many motherboards not use this type of RAM or that much? What's actually stopping it from using this much? Is it the BIOS software? Is it because the motherboard runs at 100MHz FSB? Is there actually a way to get around this via a modified BIOS? I'm a bit of a fan of the Vectras and even the latest PIII VL400 can only use 512MBs of RAM and that as far as I know can use 133MHz FSB from the processor. So what's stopping it from using 512MB chips? From what I read since I don't have one of these models in my possession is that it can only use a max of 512MBs via 2x256MB RAM sticks. Does anyone here know more details on this and why it has to be this way? When it comes to internet applications, it's really not processor speed that's your enemy, it's the amount of RAM you have since even a few tabs open can consume close to a gig, depending on what you're looking at. Right now, Palemoon on my main machine is taking up close to 600MBs of RAM, that's more than my Vectra has in its entirety.

 

So, does anyone here actually have experience in this matter? Is there a way to actually fix this or is it more of a hardware limitation than a BIOS limitation? I was able to upgrade my HP Vectra VEi8 BIOS that was modded by Wim's Team to break the 32GB barrier since the computer would hang if you installed a 40GB or larger hard drive but I think that's more of a software thing, so the only reason I bring it up is that it's not impossible to mod this stuff, but is modding something that could be done to overcome this limitation or as I said before, is it really a hardware based limitation?

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Yeah I remember using a Dell Optiplex Pentium III desktop with a maximum of 512 MB of RAM that was addressable..  Now I never tried putting two 512 PC133 DIMMs in it, so I just had two 256 MB DIMMs.  It worked well with Windows 2000 I will say.

:)

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Yeah I remember using a Dell Optiplex Pentium III desktop with a maximum of 512 MB of RAM that was addressable..  Now I never tried putting two 512 PC133 DIMMs in it, so I just had two 256 MB DIMMs.  It worked well with Windows 2000 I will say.

:)

Was it a Dell Optiplex GX1xx? I have the GX110 and it can only take up to 512MBs of RAM. If you place a 512 stick in it, I believe either the light on the panel stays amber or it beeps, I can't remember which it is. Those machines are solid as a rock though, that I will say for sure!

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  • 2 weeks later...

The Compaq Deskpro EN suffers with this same limitation - I believe it has the same chipset. It's a shame. Those older Pentium IIIs are still quite capable for daily usage otherwise.

 

I have quite a few laptops with the Intel 915 chipset. They're all limited to a max. of 2GBs of DDR2 for that reason, even though the desktop version of the 915 will address up to ~3.5GB. I did try 3GB of RAM in one laptop, Windows 7 reports 3GB of RAM, but states that 2GB is usable. The BIOS states 2GB of RAM. Hmm...

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  • 2 weeks later...

 Windows 7 reports 3GB of RAM, but states that 2GB is usable.

I only heard of such a glitch with processors that have an integrated memory controller.

 

I only heard of that with socket 1366, socket 1156, socket AM3 and later platforms.

 

It seems to be the most common with Core i-series processors. It was believed to be a problem with the CPU pin contact.

 

I saw one report of an insane problem of this type, such as "8 GB 2 GB usable".

 

This kind of thing is reported over at overclockers.com, IIRC. 

 

It wasn't common on pre-Core-i-series-era platforms.

Edited by RJARRRPCGP
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A friend of mine has an early tri-channel i7 mb with six slots (some had three). He had lots of trouble getting the DDR3 ram to work at full speed, but all 3x2=6GB (and later 6x4=24GB) were recognized.

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  • 2 weeks later...

I think it has to do with the memory controller ( just pulled that out of thin air ) or the bus itself. Many motherboards from the 1990's was easy to update the bios and thus could have more RAM to use. Again this was back in the dark ages when 64bit was not 32bit compatible. So it was ramdom ( you get it ) to run into these problems unless you really needed the RAM.

Again Amiga and Apple at this point was the dominate in the RAM department. As it was needed for mostly high end graphics production. Which was usually a computer being used between a compatible device similar to a recording studio or a PC-VCR ( which I sadly own ). Most windows users barely knew or acknowledged anything about RAM. By most users I am to say the self-proclaimed techie you would run into related field of studies/professionalism.

Many people including myself usually owned one of the many Compaq or even sadder the HP clones. Gateway E-machines ( in my case ) had an updatability to 1Gig at least ( or was it 512MB ). Now I am not lying to you but this was my primary computer during my later high-school and college years. I sure did enjoy every bit of that computer and it's 1990's space-age looking self. Enough about my sad life.

Point being is that running windows 98 is far under-power for these space age clones..... abominations. In my opinion these machines from the 1990's is what is making up most of useless junk-pile in today's world. I prefer the stylization of the 1990's PC days but they sure are ugly in the heat department. Right now those Gateway mini's are currently the most popular computers from those days.

Edited by ROTS
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A friend of mine has an early tri-channel i7 mb with six slots (some had three). He had lots of trouble getting the DDR3 ram to work at full speed, but all 3x2=6GB (and later 6x4=24GB) were recognized.

The 6 GB capacity is typical of triple channel. Coming across 6 GB almost always means a triple channel system, which I'm only aware of socket 1366 using and maybe some other Intel high-end platforms...

 

And it looks like nForce 2 may only support 3 RAM slots and thus 3 GB at max...

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 I prefer the stylization of the 1990's PC days but they sure are ugly in the heat department. 

Not like 2000s CPUs! Starting in the early-2000s, heatsinks had to exponentially be bigger to cool down CPUs at factory clocks! 

 

1990s CPUs usually required nothing more than a tiny heatsink and fan! 

Edited by RJARRRPCGP
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  • 9 months later...

Check the datasheet of the North Bridge. For the Intel 815ep the limit is 512MB, possibly because it only outputs so many address lines. Other North Bridges do access more Ram, especially a Via chipset for the Tualatin PIII. It's just that I hate Via chipsets after having had piles of problems.

Yes, a PIII Tualatin 1400MHz pushes W2k very well - but plain W2k on the Internet would be too risky for a normal user, and Xp+antivirus+browser don't run properly in 512MB. That's the very reason why I assemble a Core 2 duo for my mom presently.

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