Should I consider density (Low/High) when purchasing DDR2 ram?

Below is an Article I found on the difference between Low Density and High Density DDR,  The Main difference comes down to compatibility, Low Density DDR almost Garrentees compatibilty with all MOBO's when High Density will only works with  limited MOBO's

Hope this Helps

Many only consider SPEED when purchasing memory and often neglect an important fact that memory DENSITY is actually even more important!
So why memory DENSITY is so important? Is it related to your system when upgrading? The answer is YES!
Breakpoint #1: 1GB PC3200 DDR module  [128Mx64]
If your system is designed for accepting DDR (Double Data Rate) memories of 184pin DIMM (usually desktops) or 200pin SODIMM (usually laptops) built, for your system to fully recognise 1GB capacity per memory slot, you need to use 'Low Density - 64Mx8 config' 1GB module. If you use 'High-Density - 128Mx4 config' 1GB module, your PC may only recognise it as HALF the size at 512MB or most of the time it will not work.

How to tell if your 1GB module is a low or high density module?
All low density 1GB modules are made with 16 chips (8 chips on each side) using 64Mx8 device.
All high density 1GB modules are made with 16 chips (8 chips on each side) using 128Mx4 device.
It costs memory manufacturers almost the same to produce Low Density 1GB modules which have 100% compatibility with all systems on the market, comparing to producing high density 1GB modules. So why would manufacturers be so foolish to produce high density 1GB modules which only have 10% compatibility with systems on the market? The reason is simple, because high density 128Mx4 devices are mainly designed for used in slower server chipset/segment (Registered) which are not designed for PC chipset/segment (Unbuffered).

JEDEC standard/guideline specifies that 64Mx8 and 32Mx16 devices are to be used to construct a 1GB Unbuffered module. Any 1GB Unbuffered module constructed by using 128Mx4 device BREAKS all the JEDEC standard/guideline in which is supposed to be designed only for Registered module. Since JEDEC doesn't want the modules to be built that way, so the companies who make them (a lot are generic and 3rd parties), don't put their company label on the Unbuffered modules.

Due to unusability and high incompatibility of high density modules with standard PC, they are FAR CHEAPER, usually about half the price when compare with low density modules and a lot of buyers have fallen into attractive CHEAP PRICE trap by High Density module sellers and have complained that they will not run at all and sellers would not accept return!

High Density module is also by far slower than Low Density module at same speed rating say PC3200/DDR400.

In summary:-

LOW DENSITY modules have 100% compatibility with ALL systems and ALL chipsets as it fully follows JEDEC guidelines.
HIGH DENSITY modules only have 10% compatibility and are VERY SLOW as it breaks all JEDEC guidelines.
This is also why almost all Branded-Name systems such as Apple/MAC, Compaq/HP, Dell and IBM only uses LOW DENSITY modules.

--

Above are 3 pictures of Low Density 1GB DIMM from Micron (MT16VDDT12864AG-40BD1), Hynix (HYMD512646B8J-D43), Samsung (M368L2923CUN-CCC) respectively.

However 90% of eBay are plagued with High-Density 1GB modules at very low price, and you will be wasting your precious time and money having to return those high density 1GB modules to your seller for refund. So AVOID those 'High-Density - 128Mx4 config' 1GB modules which is usually UNBRANDED and is NO NAME!

 

Breakpoint #2: 512MB PC2700 DDR module or 512MB PC100/PC133 SDR module [64Mx64]
Many has been MISLEAD by the myth that PC133 modules would not work on older spec PC100 systems which can only take PC100 spec modules. Well, this is not exactly right, because higher speed modules are ALWAYS backward compatible in speed with slower system, and the problem source is the DENSITY of each of the black memory chip (sometime also known as device) that are used to build the complete memory module. **Note that certain motherboard manufacturers have practically hard-coded the memory speed and hence the use of higher speed modules would cause their system to become unstable, in this situation you must conform to using the required lower speed module, is especially true on systems with built-in, non-removable memory such as Apple & Gateway.


If your system is designed for accepting SDR (Single Data Rate) memories of 168pin DIMM (usually desktops) or 144pin SODIMM (usually laptops) built, for your system to fully recognise 512MB capacity per memory slot, you need to use 'Low Density - 32Mx8 config' 512MB module. If you use 'High-Density - 64Mx8 config' 512MB module, your PC may only recognise it as HALF the size at 256MB or most of the time it will not work.

The same principle applies to 512MB PC2700 DDR module especially SODIMM for laptop that takes 2x512MB = 1GB maximum configuration.

How to tell if your 512MB module is a low or high density module?
All low density 512MB modules are made with 16 chips (8 chips on each side) using 32Mx8 device.
Some low density 512MB modules are made with 16 chips (8 chips on each side) using 16Mx16 device.
All high density 512MB modules are made with 8 chips (8 chips on one side with the other side blank OR 4 chips on each side) using 64Mx8 OR 32Mx16 device.
In this case, it still costs memory manufacturers almost the same to produce all versions of these chip, but low density module always requires DOUBLE the amount of chips to make the same 512MB module than high density. Hence low density modules are usually double the price of high density modules of the same capacity.



Kingston KTC-EN133/512

 

Breakpoint #3: 256MB PC100/PC133 SDR module [32Mx64]
Many has been MISLEAD by the myth that PC133 modules would not work on older spec PC100 systems which can only take PC100 spec modules. Well, this is not exactly right, because higher speed modules are ALWAYS backward compatible in speed with slower system, and the problem source is the DENSITY of each of the black memory chip (sometime also known as device) that are used to build the complete memory module. **Note that certain motherboard manufacturers have practically hard-coded the memory speed and hence the use of higher speed modules would cause their system to become unstable, in this situation you must conform to using the required lower speed module, is especially true on systems with built-in, non-removable memory such as Apple & Gateway.

If your system is designed for accepting SDR (Single Data Rate) memories of 168pin DIMM (usually desktops) or 144pin SODIMM (usually laptops) built, for your system to fully recognise 256MB capacity per memory slot, you need to use 'Low Density - 16Mx8 config' 256MB module. If you use 'High-Density - 32Mx8 config' 256MB module, your PC may only recognise it as HALF the size at 128MB or most of the time it will not work.

How to tell if your 256MB module is a low or high density module?
All low density 256MB modules are made with 16 chips (8 chips on each side) using 16Mx8 device.
Most high density 256MB modules are made with 8 chips (8 chips on one side with the other side blank OR 4 chips on each side) using 32Mx8 device.
Some high density 256MB modules are made with 8 chips (4 chips on each side) using 16Mx16 device.
Some even higher density 256MB modules are made with 4 chips (4 chips on one side with the other side blank OR 2 chips on each side) using 32Mx16 device.
In this case, it still costs memory manufacturers almost the same to produce all versions of these chip, but low density module always requires DOUBLE the amount of chips to make the same 256MB module than high density. Hence low density modules are usually double the price of high density modules of the same capacity.