Dell Dim. 8400 w/ 2*512MB. Can I add ONE 1GB DDR?

  • Thread starter Thread starter dean
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D

dean

Dell site says I should add two slots worth, either 2*512 for an
additional gig, or 2*1GB for 2 gig. They say that if I add only one 1GB
chip, then it may not perform so well. Is this true and how bad is the
problem?

Thanks!

Dean
 
"dean" said:
Dell site says I should add two slots worth, either 2*512 for an
additional gig, or 2*1GB for 2 gig. They say that if I add only one 1GB
chip, then it may not perform so well. Is this true and how bad is the
problem?

Thanks!

Dean
Click to expand...

According to one Dell page I looked at, your motherboard has
a 925X Northbridge. You can use developer.intel.com, chipsets,
select a chipset, then technical documents, to find a memory
guide for an Intel chipset.

Page 11 of the guide here, shows it is possible to place
two 512MB sticks on one channel, and a single 1GB stick
on the other channel. This is called "Dual-Channel Symmetric".
As long as the sum of the quantity of memory is the same
on each channel, it is happy. Dual channel symmetric is
faster than a single channel mode.

http://developer.intel.com/design/chipsets/applnots/302344.htm

With those same three sticks, if you place them in the wrong
slots, it is also possible for you to end up with virtual
single channel mode. When you get your new 1GB stick, you can
actually test the difference in performance between the slower
and faster modes. (Just stick a 512MB and a 1GB stick on the
same channel, to mess it up :-) Stick the remaining 512MB
stick on the other channel.)

Make sure you get your memory from a branded source. When
neither the module nor the chips have a brand on them (blanks),
you have no way of knowing what you are getting. I've had two
batches of cheap RAM go bad, and the rest of my branded memory
(a lot of it Crucial) is still working fine.

If you want more reading material, find the section entitled
"Memory Organization Modes" in the 925X Northbridge datasheet:

http://developer.intel.com/design/chipsets/datashts/301464.htm

Dual Channel Symmetric Virtual Single Channel
(balanced qty per channel) (unbalanced qty per channel)

Ch.A Ch.B Ch.A Ch.B
512MB 1GB 1GB 512MB
512MB 512MB

HTH,
Paul
 
Hi Paul,

Wow that was a great reply! Thanks! It makes sense.

Ok so let me make sure this is right. I have 2 pairs of slots, each
pairs is one light and one dark color. The two light slots are one
channel, and the 2 darks slots are the other channel, right?

Right now from Dell there are two 512MB's, in the two dark slots. I
take it this is wrong, as it is single channel? Shouldn't they both be
in different channels, for parallel use?

Cheers,

Dean
 
Ooops I think I got that wrong. If this is the order:

CPU
1 Blue
2 White
space
3 Blue
4 White

Does this mean that Channel 1 is Blues 1 and 3, and channel 2 is whites
2 and 4?
 
"dean" said:
Hi Paul,

Wow that was a great reply! Thanks! It makes sense.

Ok so let me make sure this is right. I have 2 pairs of slots, each
pairs is one light and one dark color. The two light slots are one
channel, and the 2 darks slots are the other channel, right?

Right now from Dell there are two 512MB's, in the two dark slots. I
take it this is wrong, as it is single channel? Shouldn't they both be
in different channels, for parallel use?

Cheers,

Dean
Click to expand...

Two slots that have the same color, are on different channels.
The color is used to guide the user to making the dual channel
compatible choice. In other words, when the two DIMMs are
placed in the two dark colored slots, they are equivalent
slots on the two different channels, suitable for
dual channel usage.

On my motherboard, it looks like this:

Ch.A Ch.B
| |
Blue Blue
| |
Black Black

I can place my two 512MB in the two black slots, or I can
place them in the two blue slots, and both of those configs
are dual channel.

When you get your new 1GB DIMM, you'll be moving the
two 512MB DIMMs next to one another. The 1GB will be
in either of the slots on the other channel. The total
memory per channel is 1GB, and the total usable
memory is 2GB dual channel. (Note - this config is
not dual channel on some older Intel chipset
motherboards, like mine. Intel added this config
only in the more recent chipsets. Other chipsets
are more strict about matching the contents of
identically colored slots. So this might not work
quite the same way, in a friend's machine.)

Ch.A Ch.B
| |
512MB 1GB
| |
512MB <none>

If at some point in the future, you get another 1GB
stick, you can do this. The total memory per channel
is 1.5GB, and the total usable memory is 3GB dual
channel.

Ch.A Ch.B
| |
512MB 512MB
| |
1GB 1GB

HTH,
Paul
 
Ok Thanks Paul, you've been most helpful.

I dont know why Dell only recommends buying them in pairs though, maybe
its just easier to say that than to explain all what you said! lol

Cheers,

Dean
 
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