High density Vs Low density problem (mobo compatibility) or defective stick ?

[vikrang]

I have gone through a lot of articles in the net which has left me totally confused with differing theories on the subject of density of RAM , its compatibility , mixing size , mixing brands , mixing latency , mixing bus speed etc. While the general rule seems to be in a dual channel mode use identical sticks in all respects for perfect compatibility and do not mix size , brand , latency or bus speed which may lower the chances of compatibility. In terms of density I have gone through umpteen posts which give differing views leaving me clueless.

First off , is there a direct correlation between density of RAM and the number of sides to which chips are embedded?. That is to say is it right to conclude all double sided chips RAM sticks are "Low Density" RAM and all one sided chip sticks are "HighDensity" RAM. In many fora , this is also wrongly referred that more the chips more the density and vice versa . Wheras logically, lower the chips ,higher would be the density and vice versa " eg for a 4 GB stick low density - 16 * 256 MB (8 chips on each side ; High density - 8* 512 MB on one side . By density you mean the amount of RAM packed in a chip . naturally 512MB in a chip is higher in density versus 256 MB in a chip,
Is this basic understanding correct?
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Next , can we mix the 2 types provided everything else is same (brand , size, latency, bus speed) only difference one stick has 16 chips of 256 MB (low density I suppose) and in another 8 chips of 512 MB . Both working out to 4096 MB in all.

Now , coming to the problem , I bought one RAM stick of the second type mentioned above (512*8), the problem is that the computer goes into a loop at startup it gets reset again and again . This problem repeats irrespective of whether it is used inn combination with the older stick or when it is used alone, meaning something is wrong with the newer one.Now , Is it a problem with RAM (defective) or Compatibility (density low vs high) . In essence I would like to know if it is my fault in choosing the wrong type of RAM or the problem in the stick with no compatiblity issues. My specs have been shared while creating my account . Anyhow I have an ASROCK H81 pro BTC mother board supporting upto 16 GB RAM with 2 slots.

 

[Darkbreeze]

I sent one of our members who is a memory expert and regularly tests memory configurations a PM so hopefully he can give you a primer on this and make it clear as mud. Heh. Seriously, he's about the best around here to explain it in a way that will clarify things a bit for you.

 

[Pinhedd]

Hi,

Most of the answers that you seek are located in my memory tutorial which can be found at the top of this forum. I'll answer each one briefly below

First off , is there a direct correlation between density of RAM and the number of sides to which chips are embedded?. That is to say is it right to conclude all double sided chips RAM sticks are "Low Density" RAM and all one sided chip sticks are "HighDensity" RAM. In many fora , this is also wrongly referred that more the chips more the density and vice versa . Wheras logically, lower the chips ,higher would be the density and vice versa " eg for a 4 GB stick low density - 16 * 256 MB (8 chips on each side ; High density - 8* 512 MB on one side . By density you mean the amount of RAM packed in a chip . naturally 512MB in a chip is higher in density versus 256 MB in a chip,
Is this basic understanding correct?

Density is the capacity of each individual chip. The most common configuration on x86 PCs is eight chips per rank. Most (but not all) DIMMs place one rank on each side of the DIMM PCB. A 4GiB DIMM can be constructed from eight 4 gigabit DDR3 SDRAM chips configured as a single rank, or sixteen 2 gigabit DDR3 SDRAM chips configured as two separate ranks.

There is a limit to the number of ranks that can be installed, so greater density does allow for greater total capacity.

Next , can we mix the 2 types provided everything else is same (brand , size, latency, bus speed) only difference one stick has 16 chips of 256 MB (low density I suppose) and in another 8 chips of 512 MB . Both working out to 4096 MB in all.

Memory that is installed on a shared bus (multiple ranks on the same channel) must have the same IO configuration (8x8-bit is the most common), the same number of banks (all DDR3 SDRAM chips have 8 banks), the same number of column addresses (1024 for 8-bit IO DDR3-SDRAM chips), and compatible data rates.

Higher density chips have more rows per bank. 4 gigabit 8-bit DDR3 SDRAM chips have 65,536 rows per bank with each row 8192 bits wide (1KiB pages). 2 gigabit DDR3 SDRAM chips have 32,768 rows per bank with each row 8192 bits wide. 1 gigabit DD3 SDRAM chips have 16,384 rows per bank with each row 8192 bits wide and so on.

DDR3 SDRAM chips that use 4-bit interfaces also use 8192 bit rows, but DDR3 SDRAM chips that use 16-bit interfaces use 16,384 bit rows (2KiB pages).

DIMMs that use chips of different IO configuration cannot be mixed. It's not possible to mix DIMMs that use 4-bit, 8-bit, and 16-bit chips.

The number of rows per bank is not a limitation for mixing and matching DIMMs and it will work most of the time.

Now , coming to the problem , I bought one RAM stick of the second type mentioned above (512*8), the problem is that the computer goes into a loop at startup it gets reset again and again . This problem repeats irrespective of whether it is used inn combination with the older stick or when it is used alone, meaning something is wrong with the newer one.Now , Is it a problem with RAM (defective) or Compatibility (density low vs high) . In essence I would like to know if it is my fault in choosing the wrong type of RAM or the problem in the stick with no compatiblity issues. My specs have been shared while creating my account . Anyhow I have an ASROCK H81 pro BTC mother board supporting upto 16 GB RAM with 2 slots.

If it doesn't work at all, even on its own, there's a good chance that it's just defective. This happens more often than you think.

EDIT:

Many older chipsets, specifically those of Intel 5 series and older, have compatibility issues with 4 gigabit DDR3 SDRAM chips. However, all Intel 6 series and newer chipsets should handle these densities just fine. However, you should ensure that your motherboard has the latest firmware installed as this often reduces problems encountered with initializing SDRAM.