Memory density configuration

[derekblankmccoy]

Ive nevero gotten it.
When they say 64meg x 64 or 32meg x 72.
Im thinking the firs number is the density of each chip, but what does the second number mean?
thanks

 

[jjyiz28]

64mb x 64.

the 2nd 64 means its 64 bits wide.

72pin edo ram is 32bit wide
30pin fpm ram is 8 bit wide

64mb x 64bits wide = 64mb x 8(8bit wide) = 512mb at 8bit wide.
for parity they add an extra chip, which equates to another 8bit wide chip,
so it would be 64mb x 72 bits wide for a 512mb chip.

i believe this has nothing to do with whether the module is single or double sided.

 

[derekblankmccoy]

Thanks
If it has nothing to with density, how do I know when I buy
I wanna buy ramsinks, but if its double sided ill have to put ramsinks on both sides, not only is it gonna cost twice as much, but i might not be able to fit them on the mobo with the sinks on both sides.

 

[jjyiz28]

most modern DDR will be double sided. there are two types of densities, the size of each of the memory chips on the module, and the cell arrangements.
this is from the anandtech FAQ.


"The second factor to consider is the organisation of the RAM cells inside each chip. There are a number of configurations available for the organisation of a single chip. Take the 128Mbit chip as an example. It can be organised as 8mbit x 16 cells, 16mbit x 8 cells, or 32mbit x 4 cells. The last configuration is classed as high density.

Much of the very cheap RAM that you see today is in the form of the final organisation (?? x 4). No Intel chipset is compatible with this RAM, regardless of the overall Mbit size of the RAM chip. VIA Apollo and K?133/266 chipsets ARE compatible with this type of RAM"


im pretty sure sellers don't tell you what the cell arrangements are which sucks