Incompatible RAM chips: the mystery of the memory

August 17, 2008 6:46 PM

To my dear friends of the hive mind: Yours truly is trying to upgrade RAM memory and running into problems with incompatible chips, slots, or both.

Here's what I'm working with:


Computer:
Acer Aspire ASI180, AMD Athlon 64 X 2 Dual Core Processor 4000+
Windows Vista Home Premium

Original RAM chip:
512 MB, DD2 DIMM, F
64TFT PO 132144.3
Made in: TAIWAN

Chip I'm trying to add:
Samsung, 1GB 2Rx8 PC2-6400U-666-12-E3
Made in China
M378T2953EZ3-CF7 0804
806080

There was another Samsung chip also, but it hasn't worked in any configuration and I figure it's bad. When I put these two chips in the motherboard in various configurations of the 4 slots, I get these results:


[512MB] - [ ] - [ ] - [ ] = Shows 512 MB in Windows

[ ] - [512MB] - [ ] - [ ] = Shows 512 MB in Windows

[1.0GB] - [ ] - [ ] - [ ] = Continued beeps on startup (memory problem)

[ ] - [1.0GB] - [ ] - [ ] = Continued beeps on startup (memory problem)

[1.0GB] - [ ] - [ ] - [512GB] = Continued beeps on startup (memory problem)

[ ] - [512MB] - [1.0GB] - [ ] = Continued beeps on startup (memory problem)

[512MB] - [ ] - [ ] - [1.0GB] = Shows 512 MB in Windows

[ ] - [ ] - [512MB] - [1.0GB] = Shows 512 MB in Windows

[ ] - [ ] - [1.0GB] - [512GB] = Continued beeps on startup (memory problem)

[ ] - [ ] - [ ] - [1.0GB] = Shows 1 GB in Windows

[ ] - [ ] - [1.0GB] - [ ] = Shows 1 GB in Windows



What I glean from this is that the 512MB and the 1GB chip do not play well together. Only in some configurations does the computer start at all with both chips in, and then it only detects the 512 MB chip. The only way to get it to see the 1GB chip at all is for it to be alone in one of the back two slots.

Here are my questions: Is there something wrong with the 1GB chip? If I get another 1GB chip, is it going to work with its brother (in one of the back slots)? And why don't they work in the front slots?

San Q very much.

posted by mjklin to computers & internet (11 comments total)

Maybe you're trying to use differing size/speed RAM DIMMs in a dual-channel board? My memory is vague on this in general, but I specifically remember having a RAM pairing problem myself:

Modules rated at different speeds can be run in dual-channel mode, although the motherboard will then run all memory modules at the speed of the slowest module. Some motherboards, however, have compatibility issues with certain brands or models of modules when attempting to use them in dual-channel mode. For this reason, it is generally advised to use identical pairs of memory modules, which is why most memory manufacturers now sell "kits" of matched-pair DIMMs. Several motherboard manufacturers only support configurations where a "matched pair" of modules are used. (Wikipedia)
posted by Ky at 7:03 PM on August 17, 2008

Try running the Crucial.com memory checker. Even if you don't buy the RAM through them, you at least know what kind of memory your motherboard will take.
posted by Yoshi Ayarane at 7:22 PM on August 17, 2008

Your computer is probably an AST180, not ASI180, and there should be a more detailed model number that you should look for and post (like EA352B, or ES322B, or whatever).

Try playing with the memory clock and timing settings in your BIOS. Also, while it is important that Windows recognizes the memory, it makes more sense to watch BIOS messages and then run Memtest to verify error free operation - you probably have to go into the BIOS and disable the boot up splash page to see the messages though. Memtest is on the Ultimate Boot CD, so if possible I'd grab that.

I'd give you more specific suggestions, but the Acer website seems to be throwing errors..
posted by Chuckles at 7:35 PM on August 17, 2008

Here's a guide to memory timing. You really don't have to understand what they all mean, you just want to compare numbers on all your memory sticks, and in general choose the slowest timing. It is always possible that the sticks you have just aren't ever going to play nice together..
posted by Chuckles at 7:39 PM on August 17, 2008

Yes, sorry, it is AST180 (my typo). Full info: AST180-UD400B

A friend suggested that the PC2-6400 chip (800Mhz) is too fast for my motherboard, that PC2-5300 (667Mhz) is the fastest it can take. Could this be part of the problem?
posted by mjklin at 7:44 PM on August 17, 2008

The 6400 should be able to run at a slower speed. I can't think of an explanation for why the 1GB stick works in only 2 of the 4 slots.
posted by PueExMachina at 7:53 PM on August 17, 2008

Finally an Acer support site that is working, but they don't seem to have the manuals for your model (I think T180 is your system, but it is pretty hard to tell, click the manuals link and you get nothing).
posted by Chuckles at 9:02 PM on August 17, 2008

Try putting the disparate memory in spaces 1/3. I vaguely remember something about that.
posted by prodevel at 9:16 PM on August 17, 2008

Ya, definitely!
I thought either 1/3 or 2/4 was already tried, but neither are in the list..

You probably have two slots of one colour, and two of another. The colours represent the memory channels, and if you have different memory sticks they should be put on the same channel (memory in channels 1 and 2 should match, and memory in channels 3 and 4 should match).
posted by Chuckles at 9:55 PM on August 17, 2008

These RAM sticks won't play nice on that motherboard. I'd try buying another stick of similar RAM. Failing that, buy another 1 GB DDR2 stick. It will probably work (unless there's really something wrong with the original 1 GB stick) and it's only going to cost you $22 or so. Vista runs better with 2 GB of RAM anyway.
posted by cnc at 11:00 PM on August 17, 2008

Thanks to all for your help...I got the other 1 GB chip replaced (finally), so now I'm up and running with 2.0 GB. Chips from different companies often do not play well together, alas...
posted by mjklin at 8:27 PM on September 4, 2008