Old Pentium 166 MMX RAM question...

[gyoung]

I've been trying to upgrade the memory on my fiance's PC. She has a IBM Aptiva 2161/C85.

I've looked up the model on IBM's website and I've read the manual up and down. It says that it takes EDO or SDRAM. It can take a maximum of 64MB. I opened up the box and there is 1 32MB DIMM in the slot. I want to add another 32MB to max out her RAM and give her a little performance boost.

As a test I slid in a spare stick of a 64MB DIMM that I had lying around. This was a PC133 stick. When it booted up, the post screen showed 48MB of RAM installed. So I went to Best Buy and bought a 32MB stick of Kingston ValueRAM for $25. When I installed this RAM it showed only 40MB of RAM in the post screen. What gives?

I did notice this:

The 64MB stick has a density of 8Mx16 (4 chips on one side of the DIMM).

The 32MB Kingston stick has a density of 4Mx64 (4 chips on one side of the DIMM).

The 32MB stick that was in the computer had 4Mx64 (8 chips on both sides of the DIMM for 16 total chips).

Any ideas? Does it not like single sided DIMMS. I've been to crucials website and other RAM websites and they always quote a very high price for the RAM. Is this because I would be buying the more expensive and more rare 32MB double sided dimm?

 

[CrimsonWolf]

Older chipsets sometimes can't properly register high density memory chips.

Unfortunately, your only option may be a double sided dimm because that would use more chips, hence a lower density per chip.

I had a very similar problem a little over a year ago, and this was the only solution I could think of.

 

[gyoung]

Isn't the density this number:

4Mx64?

How does this work? Or how do you interpret this? Because the original 32MB stick was 4Mx64 and so was the other one.

If I do have to buy a double sided DIMM is there anyplace cheap to get a 32MB stick?

 

[Workin']

You probably need a double-sided DIMM. Crucial's web site is the best place to figure out what you need. They never recommend something that is more expensive than the minimum you need. For example, if your machine will work with the cheapest stuff they sell or something more expensive, they will recommend both and let you decide. You could also call their toll-free number and talk to a live person who could probably answer all your questions for you.

 

[Whitedog]

To calculate Chip density.
take the size in MB(32), multiply by 8(bits), divide by number of chips(16). This will give you the chip density size of the chips used... Hence a 32MB double-sided 16 chip DIMM would be.

32 x 8 = 256 / 16 = 16

16MegaBit chips

With an Old PC like that, you'll probably have to use 16Mbit chip DIMMS... or 16 chip 32MB stick

It's possible if you did a bios update that it would properly recognize 64MBit chip DIMMS. dunno. But most certainly won't recognize 128Mbit chips.

 

[mschell]

You might try running the new RAM by itself, if it registers corectly then chucking the old memory might be a good option. It's cheap enough for 32 MB to do this, I would try running a single 64MB module. I've run new single sided PC133 memory in older Tyan socket 7 MB's with no problems.

 

[gyoung]

Found this information in the FAQ at this site: http://www.ping.be/bios/

I'll just have to try my luck at e*ay or in the trading forum...



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30. Why won't my VX motherboard recognize xxMB DIMMS/SIMMS?

The Intel VX doesn't have enough Memory Address lines to drive the higher integration DRAM technology, be it EDO or SDRAM. 16-MBit is the highest density supported, while the parts on a 64-MByte EDO SIMM are 64-MBit (eight chips)

Do the math - count the SDRAM chips on your DIMM (the large ones) [if they're ECC DIMMs, round down to the nearest power of two], and compute:

((total capacity in MByte)*8)/(number of chips)

The result is the density in MBit of the SDRAM components used.

Examples:

32-MByte DIMM with 16 chips: 32*8/16=16, usable with Intel VX.

128-MByte ECC DIMM with 18 chips - round down to 16, 128*8/16 = 64, not usable on VX.

As current production is 64- or 128-MBit densities, the bottom line of all this is that SDRAM support in Intel VX is useless with today's DIMMs.

Also, in order to have your board recognize 32Mb per DIMM, you'll need the 16-chip versions. If you have the 8-chip version, only 8Mb (your case) will be recognized.

Remember, it's not a memory problem; it's a chipset limitation. And no, this can't be fixed by a BIOS update.
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