DDR manufacturer

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I am thinking of adding some RAM to my PC, and I was reading my

motherboard manual about RAM.  It says you should try to get 2 chips

from the same manufacturer if you are going to put them in a pair of

DDR slots.  How important is it that they are from the same


Re: DDR manufacturer

bob@coolgroups.com wrote:
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There are two requirements.

1) There is what the motherboard really needs technically.

2) There is what the BIOS feels it needs, to make dual channel work.

Sometimes those aren't the same thing. For example, there was one
AMD motherboard, where the BIOS was checking the PCB revision field
stored in the SPD EEPROM on the DIMM. Which is a stupid thing to do,
and totally unnecessary. A guy bought two DIMMs that looked like
they matched, and yet the BIOS rejected them as not matching. That
doesn't happen too often.

The most constrained motherboards, are the ones that operate in 128 bit
mode. That is where DIMMs in separate channels, receive exactly the
same address and command information. For such motherboards to work
in dual channel, they have restrictions on DIMM population. For example,
using two DIMMs or four DIMMs, is all that is allowed. They don't allow
three DIMMs in those boards.

In such a case, the rows, columns, banks, and ranks of the DIMMs have
to match. That is all that is needed worst case. The color of the DIMMs
doesn't matter. The brand doesn't matter. The chips have to match, in
the above stated way, so that when they receive identical control info,
they respond in exactly the same way.

Some motherboards have a more relaxed requirement. Those motherboards
feed different information to each channel. In those cases, all that
needs to match, is the total memory quantity on each channel. For example,
on one of those motherboards, you could stick two 512MB DIMMs on
one channel, and a single 1GB DIMM on the alternate channel, and
it would run dual channel.

Rows, columns, and banks, are the three internal dimensions of a
memory chip. A memory array is addressed with rows and columns.
Inside a memory chip, there might be four banks (four separate
arrays). To address a chip, the row number, column number, and
bank number are fed to the chip.

Memory chips work side by side, to make a wider structure. If you
stick (8) 8 bit wide chips next to one another, you get a 64 bit
wide array. That happens to be the width of the memory bus, connected
to the DIMM.

If there are sixteen chips on a DIMM, eight are in one array and eight
are in a second array. For purposes of unique terminology, these
are referred to as two "ranks". An imprecise way to think of it,
is "double sided" = "dual rank". So you want the "sidedness" of the
memory DIMMs to match. You aren't matching, for example, if one
channel has a single sided 512MB DIMM and the other one has a
double sided 512MB DIMM. Those would actually need different
row, column, and bank numbers to work.

So, insisting on using exactly the same memory product (same
color, model number blah blah blah), helps ensure that the
rows, columns, banks, and ranks match. It also helps in cases
where the BIOS is poorly designed, and the BIOS is being a bit
too picky about what is a matching pair of DIMMs.

The user manual may give hints about how picky the architecture is.

If you mention the motherboard in question, I can give more
info if needed.


Re: DDR manufacturer

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Not important at all. They need to have the same 'timings'. CAS Latency etc.
Typically it is easier to buy 1 DIMMS from the same batch to guarantee the
same timings, but a well labelled product from Samsung will potentially
appear electronically identical to a Sandisk, or OCX etc product. Its all in
the numbers!

Re: DDR manufacturer

b...@coolgroups.com wrote:

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Only 2 chips?  Do you plan to solder them to the modules?  Because a
module is a small circuit board, usually anywhere from 4-18 memory
chips on it, and chips those things in the square or rectangular black
plastic packages and soldered to the circuit boards.

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Usuually not very, and with some brands of modules matched pairs
aren't any more compatible with one another than modules from separate
manufacturers are.  If you want to be assured of getting good modules,
buy only those with chips that were branded by a chip manufacturer
(i.e., Samsung, Powerchip, Hynix, Infineon, Micron, Winbond, Nanya,
etc.) and not branded by a module manufacturer (Kingston, Corsair,
OCZ, Mushkin, etc.).

Re: DDR manufacturer

bob wrote:
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Modules or DIMMs not chips. Use the Crucial or Kingston tools which will
provide a number of compatible choices.

http://www.crucial.com /
http://www.kingston.com /

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I prefer to buy modules of the same size and model number, but strictly
speaking it's not always necessary. Mixing PC2-6400 and PC2-4200 will
default to a memory clock of 133MHz rather than the 200MHz of PC2-6400.
Different sized modules of the same speed rating usually work together.

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