256MB chips. 16Mx16, 32Mx8, 64Mx4. What's the difference?

[WoundedWallet]

I'm hitting again on this subject.

A while ago someone said that their cheap 256MB chip didn't work with an old mobo. The reason being on how the chip was made.

I imagine that he was refering to a 256MB unit made out of 16-16MB chips.

Anyone can confirm such known problem?

Also, if I'm buyinmg a chip on a site, how can I tell how the chip was made by its description? When they say "32x64" are they meaning 8-32MB chips on a non-ECC(64) unit?

Thanks,
WW

 

[rockhard]

"32x64" they are meaning 32x 8mb chips (double decker dimm i think)

1x64 = 8 megabytes
2x64 = 16
4x64 = 32
8x64 = 64
16x64= 128
32x64= 256 megabytes

a 64bit wide chip is 8 megabytes

feel free to correct me if im wrong as its a while since ive done this,

rockhard =)

 

[hans007]

yeah i've seen a 32 by 64 , its 32 chips , monster, usually would be buffered though. The new chips are 128mbit so they only had 16 chips, but a lot of older boards cant read them

 

[rockhard]

hans007

when u say that these 128bit wide chips cannot work on older boards is that because they need to be running on a motherboard that has a 128bit Memory Controller Chip?
If so, do these 128bit Memory Controller chips still work on a 64bit data bus but have a 128 bus connection to the ram?

rockhard =)

 

[Gunbuster]

The mega bit is like mega byte (size), nothing to do with external interface bit width.

 

[Mark R]

The designation '32Mx64' means a 256 MB DIMM - you can tell nothing else from that.

In particular, it does not tell you the types of chip used to make the module.

32Mx64 means that your module has a 64 bit data path (all DIMMs have a 64 bit data path - or 72 bits for ECC modules), and that it stores 32 Mwords - each word in this case being 8 bytes (64 bits) wide, for a total of 256 MB.

One way of making a 256 MB DIMM would be to use 8 32Mx8 chips, thereby giving a 32Mx64 module. The problem with this, is that some older motherboards don't support chips with such a large number of words. In this case you would need to use 16 16Mx8 chips arranged as 2 lots of 16Mx64, or 32 8Mx8 chips arranged as 4 lots of 8Mx64.

 

[nEoTeChMaN]

It is always start with 8 Bit.

For example: 16 x 64

Take the 64 bit and divide by 8 bit which gives you 8.

Take the 8 and mulitply by 16 which gives you 128MB.

The A+ taught me that.

 

[WoundedWallet]

MarkR, thanks for the clear info.