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ASRock P4V88, DDR DIMM's

 
 
mborgbusuttil@onvol.net
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      03-17-2008
My PC motherboard is an ASRock P4V88. I was using a DDR DIMM purchased
last year(512Mb pc3200). This year I purchased 3 DDR DIMM's of the
same brand and the same specifications and added them, however I could
not set my motherboard to "dual channel". I am suspecting that
although they have the same specifications as the one I bought last
year they may not be entirely identical to it and the motherboard is
detecting this difference. In fact their outward appearance is
slightly different. Now my motherboards manual is saying that when all
four memory banks are filled the DDR DIMM's have to be identical. Do I
risk damaging my motherboard, or is it just an issue of stability?
 
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Paul
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      03-17-2008
http://www.velocityreviews.com/forums/(E-Mail Removed) wrote:
> My PC motherboard is an ASRock P4V88. I was using a DDR DIMM purchased
> last year(512Mb pc3200). This year I purchased 3 DDR DIMM's of the
> same brand and the same specifications and added them, however I could
> not set my motherboard to "dual channel". I am suspecting that
> although they have the same specifications as the one I bought last
> year they may not be entirely identical to it and the motherboard is
> detecting this difference. In fact their outward appearance is
> slightly different. Now my motherboards manual is saying that when all
> four memory banks are filled the DDR DIMM's have to be identical. Do I
> risk damaging my motherboard, or is it just an issue of stability?


A motherboard has two options, when presented with non-matching
DIMMs.

1) Operate in virtual single channel mode. Each of the four DIMMs
work, but are accessed only one at a time. As if the four
DIMMs are sitting on a single channel. Operation will be
stable, as it is designed to work that way (i.e. single channel
operation is one of the options put in there by design).

2) For chipsets which have "strict matching" policies, the
non-matching stick may be ignored/rejected by the BIOS.
For example, if I had a matched pair in A1-B1 and a
mismatched pair in A2-B2, the A2-B2 ones may be ignored.

In terms of matching, the parameters of interest are
rows, columns, banks, ranks.

Inside the memory chip, are the rows, columns, and banks.
Some memory chips are quad bank, meaning the memory is
logically partitioned into four chunks. The rectangular
dimensions of each chunk, is "rows x columns".

At the module level, they arrange memory chips, such that a
64 bit wide memory array is constructed. For example, you
could use 8 chips each 8 bits wide, to do it. If a DIMM
had 16 chips total, of the 8 bit wide variety, then there
are enough chips for "two ranks". That is popularly
described as "double sided". Each rank is a 64 bit wide array.
And the two ranks sit in parallel to one another.

In recent years, some single sided 512MB DIMMs have become
available. The majority (older ones) would be double sided
512MB DIMMs. The chip density difference is a factor of 2,
meaning the "rows x columns" on those two different kinds
of DIMMs, will not be the same. That would be why the
BIOS is not treating such a case, as dual channel.

A single sided 512MB, is not the same as a double sided 512MB.
The single sided would have a total of 8 chips, the
double sided a total of 16 chips (assuming no ECC).

The user manual usually has some hints, about whether the
chipset is (1) or (2). But the feedback you're getting
from the BIOS, as to whether all four are matched, would
also be a clue.

http://download.asrock.com/manual/P4V88.pdf

There is no risk of damage, as they are all DDR DIMMs,
have the same voltage ratings, the same signal names.
Pin compatible in other words. The result, might be
slightly less performance or less total memory, than
you would otherwise expect. Annoying but no damage.

Buying a fourth, to match the other three, would be
a possible solution. But even so, there are no
guarantees in life, when it comes to BIOS design.
Sometimes, an early BIOS, will have bugs with respect
to memory configuration, and the BIOS might still
complain. So while you can do your best to match them,
there is still a chance of some odd behavior. In
that regard, Googling for previous experience or
looking in private forums, is one way to discover
how the thing works or doesn't work.

Paul
 
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mborgbusuttil@onvol.net
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      03-18-2008
On Mar 17, 8:43*pm, Paul <(E-Mail Removed)> wrote:
> (E-Mail Removed) wrote:
> > My PC motherboard is an ASRock P4V88. I was using a DDR DIMM purchased
> > last year(512Mb pc3200). This year I purchased 3 DDR DIMM's of the
> > same brand and the same specifications and added them, however I could
> > not set my motherboard to "dual channel". I am suspecting that
> > although they have the same specifications as the one I bought last
> > year they may not be entirely identical to it and the motherboard is
> > detecting this difference. In fact their outward appearance is
> > slightly different. Now my motherboards manual is saying that when all
> > four memory banks are filled the DDR DIMM's have to be identical. Do I
> > risk damaging my motherboard, or is it just an issue of stability?

>
> A motherboard has two options, when presented with non-matching
> DIMMs.
>
> 1) Operate in virtual single channel mode. Each of the four DIMMs
> * * work, but are accessed only one at a time. As if the four
> * * DIMMs are sitting on a single channel. Operation will be
> * * stable, as it is designed to work that way (i.e. single channel
> * * operation is one of the options put in there by design).
>
> 2) For chipsets which have "strict matching" policies, the
> * * non-matching stick may be ignored/rejected by the BIOS.
> * * For example, if I had a matched pair in A1-B1 and a
> * * mismatched pair in A2-B2, the A2-B2 ones may be ignored.
>
> In terms of matching, the parameters of interest are
> rows, columns, banks, ranks.
>
> Inside the memory chip, are the rows, columns, and banks.
> Some memory chips are quad bank, meaning the memory is
> logically partitioned into four chunks. The rectangular
> dimensions of each chunk, is "rows x columns".
>
> At the module level, they arrange memory chips, such that a
> 64 bit wide memory array is constructed. For example, you
> could use 8 chips each 8 bits wide, to do it. If a DIMM
> had 16 chips total, of the 8 bit wide variety, then there
> are enough chips for "two ranks". That is popularly
> described as "double sided". Each rank is a 64 bit wide array.
> And the two ranks sit in parallel to one another.
>
> In recent years, some single sided 512MB DIMMs have become
> available. The majority (older ones) would be double sided
> 512MB DIMMs. The chip density difference is a factor of 2,
> meaning the "rows x columns" on those two different kinds
> of DIMMs, will not be the same. That would be why the
> BIOS is not treating such a case, as dual channel.
>
> A single sided 512MB, is not the same as a double sided 512MB.
> The single sided would have a total of 8 chips, the
> double sided a total of 16 chips (assuming no ECC).
>
> The user manual usually has some hints, about whether the
> chipset is (1) or (2). But the feedback you're getting
> from the BIOS, as to whether all four are matched, would
> also be a clue.
>
> http://download.asrock.com/manual/P4V88.pdf
>
> There is no risk of damage, as they are all DDR DIMMs,
> have the same voltage ratings, the same signal names.
> Pin compatible in other words. The result, might be
> slightly less performance or less total memory, than
> you would otherwise expect. Annoying but no damage.
>
> Buying a fourth, to match the other three, would be
> a possible solution. But even so, there are no
> guarantees in life, when it comes to BIOS design.
> Sometimes, an early BIOS, will have bugs with respect
> to memory configuration, and the BIOS might still
> complain. So while you can do your best to match them,
> there is still a chance of some odd behavior. In
> that regard, Googling for previous experience or
> looking in private forums, is one way to discover
> how the thing works or doesn't work.
>
> * * Paul


Thanks Paul for a very clear explanation. Youv'e put my mind at rest.
 
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