Low Density vs High Density

[Garet Jax]

Hello all,

I am trying to understand the difference between low and high density RAM. I have done some reading and found that it is either too technical (don't understand it) or not technical enough (don't give enough information).

Can you please help me understand it better?

How can someone definitively tell whether RAM is high density or low. Some people said it is the number of chips on the RAM stick. Some have said it is whether or not chips are on both sides of the stick.

What is it? Thanks.

 

[SuperNaruto]

great that no one explain this to you on the other threads..

You can only have so many chips wired together on a single data pin of a data bus. In large servers/mainframes with huge memory requirements this starts to become an issue. Using 64Mx4 chips you have half the number of chips on each data pin. As a result you can have twice as many chips, thus twice as much RAM on the same bus.

say you got 512mb on 1 dimm

64 x 8 = 512 (8 chip total on 1 side)
32 x16 = 512 (16 chip total, 8 on each side)

but whats conside low density ? depends on dimm..

1gb
64x8 (2 side)
128x4 (2 side)

same with 256mb
32x8
64x4

32Mx8 based chips use 10 column control signals (A0 to A9).
64Mx4 based chips use 11 column control signals (A0 to A9 plus A11).
A large number of motherboards don't support using A11 as a column signal and so can only detect half the capacity.


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 1GB modules are mainly manufacturing process rejects/seconds that cannot be made as a low density modules. It is very much like Intel CPU, those CPU that cannot be made as Pentium 4 CPU become a slower bus Celeron CPU instead, by a down-binning process.

High Density module is by far much slower than Low Density module at same speed rating say PC3200/DDR400. A lot of users have fallen into attractive CHEAP PRICE trap by High Density module sellers and have complained that they are either VERY SLOW and/or will not run at all and sellers won't accept return!

High density modules are FAR CHEAPER, less than half the price when compare with low density modules and hence high density modules will NOT work on 90% of today's PC chipsets that require and can only use 'Low Density - 64Mx8 config' 1GB modules.