Memory Question 2

[muthabored]

I'm looking to upgrade the RAM in a desktop that I just purchased. The RAM that's in the sockets is (2) sticks of 256 DDR 400 PC3200U - does the U mean it's UNBUFFERED? I've been searching for the differences between unbuffered & registered, as I don't want to purchase something that's incompatible with my system (HP Pavilion a818n). Thanks in advance!

 

[dementg]

I think the only major difference between the typical P2/P3 chipsets regarding RAM is that the older 440bx can handle up to 8 logical "rows" (sides) of 128MB each, but the i810/i815 are limited to 4 sides of 128MB each, which is why it maxes out at 512MB. Usually those boards only have 2 memory slots to eliminate confusion about it.

A double sided and "unbuffered" 256MB module which uses the "16Mx8" chip types would be correct for these chipsets and should most likely work. Unfortunately it's not easy to find out what chip types are being used until you have the thing in your hands. If you stick to reputable brands then you can safely assume that any PC133, double sided, 8 chip per side, 256MB module should be good though. As far as I know the only double sided 16-chip modules that still have incompatible chips are generic no name stuff.

============
If it's 256MB PC133 double sided, with 16 major chips, 8 on each side (not 9), and branded by somebody like Kingston, Micron, Crucial, Corsair, etc. then it should be fine. Sticking to good brands reduces the number of ways you can get fooled.

 

[cdogg]

dementg,
I believe the term you are looking for is "banks" not rows. Each side of a double-sided module is called a bank. Each bank has multiple rows and columns.

Also, I don't quite follow your logic about the 8 "rows" versus 4. Both the 440BX and the 810/815 chipsets max out at 512MB. The 440BX can support more than 512MB only when "registered" DIMMs with 8 memory rows are used (the max in that case is 1GB). Other than that exception, it doesn't appear to give any other advantage with non-registered DIMMs.

...but the i810/i815 are limited to 4 sides of 128MB each...
Usually those boards only have 2 memory slots to eliminate confusion about it.

I've never seen an 815 board with only two slots. In fact, the whitepaper design for the 815 lists the standard configuration at 3 DIMM slots, each supporting both single and double-sided modules. Check page 21 here:

http://download.intel.com/design/chipsets/designex/29835002.pdf

dementg, I know you have a lot of experience when it comes to memory. I'm not doubting that you have a better understanding than I do. However, I don't want to see the 815 chipset being placed in the same group as the 810 and getting overshadowed. The 815 significantly improved memory performance and tolerance. It was the first board I can remember having very little trouble throwing a mixture of single and double-sided modules at. I can't say the same about the 440BX which preferred double-sided DIMMs when referring to 128MB or 256MB modules.

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Albert Einstein
[tab][navy]For general rules and guidelines to get better answers, click here:[/navy] faq219-2884

 

[dementg]

The term "rows" is used in the Award BIOS startup when it reports the locations of the memory in your system. I also was just reading the Intel 440BX datasheet and noticed they also use the term this way. However the term "bank" might be better since it doesn't cause a conflict with the lower level terminology of rows and columns.

Also, I don't quite follow your logic about the 8 "rows" versus 4. Both the 440BX and the 810/815 chipsets max out at 512MB. The 440BX can support more than 512MB only when "registered" DIMMs with 8 memory rows are used (the max in that case is 1GB). Other than that exception, it doesn't appear to give any other advantage with non-registered DIMMs.

I just checked the datasheet, and noticed you're right. Officially the 440BX is limited to 512MB of unbuffered memory.

I was surprised to see the unbuffered limit is so low - I've never encountered a board that didn't handle a full load of memory when running at stock speed. Most of them are indifferent even at 133MHz, but sometimes they have trouble with the POST count. I've always tested boards using memtest86 with a full load of unbuffered memory (768-1024MB), and never had an error at 124MHz or below. Even at 133MHz errors are rare. Suffice to say the 440BX official specs are ridiculously conservative.

You have to push really hard before you have any RAM glitches on the 440BX. The supposed 512MB limit isn't really an issue at stock speeds, and a million people have probably violated it without ever knowing they were cheating a rule. But that IS the official spec, much to my surprise.

 

[Airpan]

Cdogg,
Dell confirmed that due to the memory not being double-sided that it wasn't going to work. They pointed me to the right memory on their site and my friend purchased it. It was installed and works. To be honest, with Dell, I have noticed odd little things with their computers and memory... this isn't the first time I have run into situations where typically it wouldn't be an issue, but for whatever reason with their machines it ends up being really tempermental.

As far as misunderstandings, this happens often with forums and perhaps there were misunderstanding on both sides. Thanks for the help again and I am relieved it is now resolved.

 

[cdogg]

Yep, that's the ticket!
Double-sided is generally MORE compatible than single-sided memory when talking about good-old PC100 or PC133 SDRAM.

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Albert Einstein
[tab][navy]For general rules and guidelines to get better answers, click here:[/navy] faq219-2884