1gb or 1.5gb RAM?

[Howie]

I have an XP Pro system with the A7N8X Deluxe board with a Barton
2500+ (not overclocked) running at its default speed (166 x 11). I
currently have two sticks of PC3200 256mb RAM (CAS 3) in slots 1 & 2
and a 512mb stick of PC3200 RAM (CAS 2.5) in slot 3. I have been led
to believe a congruent amount of like memory in slots 1+2 and 3 (the
combination of what is 1 and 2 should equal what is in 3) will allow
dual channel performance.

My dilemma is whether to add another 512mb RAM to the system. I am
finding I need to add memory in order to accommodate a variety of
memory-intensive applications which I run simultaneously and have open
for long stretches at a time. The system becomes somewhat sluggish as
the RAM ceiling is met and exceeded. There are some good deals on
PC3200 RAM at the moment and purchasing a couple sticks of 512mb would
allow the size upgrade desired. The tradeoff, I believe, is I would
lose dual channel performance as the congruency size-wise would be
lost (1024 and 512).

So, is the dropoff in performance from losing this dual channel
capability a greater factor than the benefit that would be derived by
adding 512mb of RAM to address the aforementioned conditions?

Thanks for your insight,


--Howie

 

[Ed Medlin]

I have an XP Pro system with the A7N8X Deluxe board with a Barton
2500+ (not overclocked) running at its default speed (166 x 11). I
currently have two sticks of PC3200 256mb RAM (CAS 3) in slots 1 & 2
and a 512mb stick of PC3200 RAM (CAS 2.5) in slot 3. I have been led
to believe a congruent amount of like memory in slots 1+2 and 3 (the
combination of what is 1 and 2 should equal what is in 3) will allow
dual channel performance.

My dilemma is whether to add another 512mb RAM to the system. I am
finding I need to add memory in order to accommodate a variety of
memory-intensive applications which I run simultaneously and have open
for long stretches at a time. The system becomes somewhat sluggish as
the RAM ceiling is met and exceeded. There are some good deals on
PC3200 RAM at the moment and purchasing a couple sticks of 512mb would
allow the size upgrade desired. The tradeoff, I believe, is I would
lose dual channel performance as the congruency size-wise would be
lost (1024 and 512).

So, is the dropoff in performance from losing this dual channel
capability a greater factor than the benefit that would be derived by
adding 512mb of RAM to address the aforementioned conditions?

Thanks for your insight,


--Howie

Really tough to say without trying it. I would assume that dual channel
would be more efficient at 1g than non-dual channel at 1.5g. Just an
assumption though. The extra 512 is not a lot of gain anyway and I wouldn't
even bother to add it unless you have found that the 1g you have is being
fully used for sure and if so, I would add another gig. If the apps you are
using are utilizing the full gig you have, I would say that another 512
would be used fairly quickly. Video editing and some memory-intensive CAD
stuff are the only things I have seen that suck up memory like you are
seeing.

Ed

 

[Howie]

Really tough to say without trying it. I would assume that dual channel
would be more efficient at 1g than non-dual channel at 1.5g. Just an
assumption though. The extra 512 is not a lot of gain anyway and I wouldn't
even bother to add it unless you have found that the 1g you have is being
fully used for sure and if so, I would add another gig. If the apps you are
using are utilizing the full gig you have, I would say that another 512
would be used fairly quickly. Video editing and some memory-intensive CAD
stuff are the only things I have seen that suck up memory like you are
seeing.

Ed

Thanks for the input. Believe it or not, I don't use the types of
applications one would normally identify as the "memory suckers" but
rather the following type of lineup:

Firefox (A dozen or so open tabs)
MS Outlook
IE
iTunes
MS Excel
Google Earth
MS Money
ActiveSync (Pocket PC synching software)
Zone Alarm
MS AntiSpyware
And a few others in the background...

I suspect part of the issue in bumping up against the current 1gb
ceiling is that some of these applications do not return resources
efficiently (at all?). I guess I am trying to avoid the need to
reboot every couple of days when I am using the system intensely for
all of (my) life's activities...

I know that 2gb is probably the best solution, but unfortunately I
don't have a 1gb stick already (read: cost prohibitive to buy 2gb of
RAM and receive little or nothing for my existing lineup of 1gb RAM).
The 1gb "kits" (2 sticks of 512mb) are priced nicely at the moment and
that is what triggered my thinking relative to upping things to 1.5gb
-- but if performance would be jeopardized due to losing the dual
channel feature, then perhaps my dilemma has been resolved.

Regards,


--Howie

 

[Custom Computers]

You can't run dual channel mode with three sticks of memory, no matter
what the size. Dual channel requires two hence the term Dual. The
memory slots are configured to run in pairs. Thats why most dual
channel boards have colored memory slots. So you can make sure you
install the memory in the proper slot to get dual channel operation.

Now running a pair of 256 sticks in there proper slots for dual channel
and a pair of 512 sticks in there proper slots should give you Dual
Channel support.

You must also remember the sticks of ram must be by the same, make,
size and layout to run in dual channel mode. They do not need to be
Dual Channel kits but these kits also have added support for operation
in dual channel mode.

 

[Egil Solberg]

You can't run dual channel mode with three sticks of memory, no matter
what the size. Dual channel requires two hence the term Dual. The
memory slots are configured to run in pairs. Thats why most dual
channel boards have colored memory slots. So you can make sure you
install the memory in the proper slot to get dual channel operation.

You can run a perfect dual channel with 3 sticks if you only match them up
so that you get the same amount of memory in the 2 channels, just as OP is
doing right now.
If there is an imbalance in ram amount in the 2 channels, only parts of the
ram will run dual channel.

Now running a pair of 256 sticks in there proper slots for dual
channel and a pair of 512 sticks in there proper slots should give
you Dual Channel support.

Not with nforce 2 that has 3 memory slots, 2 for the 1. channel, 1 for the
other.

You must also remember the sticks of ram must be by the same, make,
size and layout to run in dual channel mode. They do not need to be
Dual Channel kits but these kits also have added support for operation
in dual channel mode.

Not necessary at all. Currently I mix old PC2100, PC2700 and PC3200 in my
rig (all Kingston valueram). Works like a charm.

 

[Greysky]

You can run a perfect dual channel with 3 sticks if you only match them up
so that you get the same amount of memory in the 2 channels, just as OP is
doing right now.
If there is an imbalance in ram amount in the 2 channels, only parts of
the ram will run dual channel.



Not with nforce 2 that has 3 memory slots, 2 for the 1. channel, 1 for the
other.



Not necessary at all. Currently I mix old PC2100, PC2700 and PC3200 in my
rig (all Kingston valueram). Works like a charm.

Hmm...it may work, but not very efficiently. If you are mixing up different
speeds / brands / types, clock skew will be killing off most of your
performance. It'd be interesting if you benchmark your memory operation with
the different combinations and then post the results.

 

[DaveW]

Wrong. Three sticks of RAM used in a motherboard precludes it running in
dual channel mode.

 

[Mark A]

Wrong. Three sticks of RAM used in a motherboard precludes it running in
dual channel mode.

You might want to first read the manual for that particular motherboard
(which only has 3 memory slots).

 

[Paul]

Hmm...it may work, but not very efficiently. If you are mixing up different
speeds / brands / types, clock skew will be killing off most of your
performance. It'd be interesting if you benchmark your memory operation with
the different combinations and then post the results.

The Nforce2 is a very flexible chipset, in fact more flexible
than just about any other chipset (only some recent Intel
chipsets come close, and AFAIK, still don't support the
composite mode that the Nforce2 has.). Like many boards in the
past, if you mix different speeds of memory, it is up to the
BIOS to pick the slowest timing spec found in each SPD, and
use that to set the timing for all sticks. A PC3200 stick is
backward compatible to the lower rates, and can run all the way
down to PC1600 if need be. (Download a memory chip datasheet
from Micron if you don't believe this.)

The Nforce2 only needs to balance the total memory in each
channel, to benefit from dual channel operation. And the
Nforce2 still continues to run, unabated, when faced with
an unbalanced combination of memories.

I have a specially modified copy of memtest86 (a three line
mod in the program), in which I test the memory bandwidth
as a function of address space. If I insert 3x512MB DIMMs,
the lower 1024MB of memory has the dual channel bandwidth,
and the upper 512MB has the single channel bandwidth. Thus,
using an unbalanced configuration, where one channel has
more memory than the other, _still_ results in 2/3rds of
the address space being dual channel. It does the dual
channel thing, for as much memory as is common to both
channels. In the 3x512MB case, one channel has 512MB and
the other 1024MB, and both channels have at least 512MB
in common, and that common portion runs dual channel

channel0 channel1

512MB <--- Top portion runs single channel
512MB 512MB <--- This section runs dual channel

Also, if you consider the bandwidths involved for a moment,
the AthlonXP has a 64 bit bus, operating at FSB400, for a
bandwidth of 3200MB/sec. Two sticks of PC3200 give a total
bandwidth of 6400MB/sec. That means the AthlonXP cannot
unleash the full potential of that configuration. That is
why the difference seen in real applications, between
single channel and dual channel, is as small as it is.
If I really needed the memory, I wouldn't hesitate to run
3x512MB, and ran Linux that way for a while.

HTH,
Paul

 

[Howie]

The Nforce2 is a very flexible chipset, in fact more flexible
than just about any other chipset (only some recent Intel
chipsets come close, and AFAIK, still don't support the
composite mode that the Nforce2 has.). Like many boards in the
past, if you mix different speeds of memory, it is up to the
BIOS to pick the slowest timing spec found in each SPD, and
use that to set the timing for all sticks. A PC3200 stick is
backward compatible to the lower rates, and can run all the way
down to PC1600 if need be. (Download a memory chip datasheet
from Micron if you don't believe this.)

The Nforce2 only needs to balance the total memory in each
channel, to benefit from dual channel operation. And the
Nforce2 still continues to run, unabated, when faced with
an unbalanced combination of memories.

I have a specially modified copy of memtest86 (a three line
mod in the program), in which I test the memory bandwidth
as a function of address space. If I insert 3x512MB DIMMs,
the lower 1024MB of memory has the dual channel bandwidth,
and the upper 512MB has the single channel bandwidth. Thus,
using an unbalanced configuration, where one channel has
more memory than the other, _still_ results in 2/3rds of
the address space being dual channel. It does the dual
channel thing, for as much memory as is common to both
channels. In the 3x512MB case, one channel has 512MB and
the other 1024MB, and both channels have at least 512MB
in common, and that common portion runs dual channel

channel0 channel1

512MB <--- Top portion runs single channel
512MB 512MB <--- This section runs dual channel

Also, if you consider the bandwidths involved for a moment,
the AthlonXP has a 64 bit bus, operating at FSB400, for a
bandwidth of 3200MB/sec. Two sticks of PC3200 give a total
bandwidth of 6400MB/sec. That means the AthlonXP cannot
unleash the full potential of that configuration. That is
why the difference seen in real applications, between
single channel and dual channel, is as small as it is.
If I really needed the memory, I wouldn't hesitate to run
3x512MB, and ran Linux that way for a while.

HTH,
Paul

Paul,

Your input does help. Thanks. I have ordered a pair of Patriot
PC3200 512mb sticks...

Thanks to the others who contributed as well, save for those
contending dual channel performance is not available with three sticks
of RAM. Posting information as fact when done from a base of
ignorance is irresponsible when there are legitimate questions in need
of valid input.

Regards,


--Howie

 

[bowgus]

With todays PCs, it's best to mix RAM (use a variety of vintages, sizes,
specs, manufacturers) to avoid problems like bsod, hair loss, impotence,
etc. Irresponsible? I don't think so. There are no stupid questions, only
stupid people (lazy ass irresponsible bozos too dull to rtfm), So, what's
yer next question?

 

[Ed Medlin]

Wrong. Three sticks of RAM used in a motherboard precludes it running in
dual channel mode.

Wrong Dave. I just read his MB specs and if he uses 3 sticks, the two will
run in dual channel and the other as single.

Ed

 

[Custom Computers]

And if two slots are running in dual channel and the third is running
single channel then its not running in total dual channel mode. thus
its impossible to run in true dual channel mode with three sticks of
ram.

You just have to laugh at bowgus's reply. Mixing of RAM types is
impossible, you can't mix DDR with DDR2 or older memory as well. All
are sized and slotted to prevent that. You can mix speeds, but then the
system is going to run at the slowest speed of all the memory installed
if you allow spd to set it. If you choose to manually set timings thats
where mixing speeds will most likely cause BSOD and memory error
messeges if you try to set the speeds at the highest timings. Also
running single sided memory with double sided memory has been known to
cause problems on some but not all motherboards. It's always best to
use matching sticks of memory. Thats why for quality Dual Channel
memory the makers not only use the same layout but they also use memory
chips from the same manufacturing batch runs.

 

[Egil Solberg]

And if two slots are running in dual channel and the third is running
single channel then its not running in total dual channel mode. thus
its impossible to run in true dual channel mode with three sticks of
ram.

OMG. With 2x 256 MB in memory slots 1 and 2 belonging to channel 1, and
1x512 MB in slot 3 belonging to channel 2 there is balance between the 2
channels, and the dual channel setup is perfect. All ram runs in dual
channel. All slots occupied and the dual channel setup is perfect in this
case.

For this and other configs, please read Paul's reply. He has tested it, and
posted the results months ago. There has been much fuss and misconseptions
around this topic until Paul cleared it out.

You just have to laugh at bowgus's reply. Mixing of RAM types is
impossible, you can't mix DDR with DDR2 or older memory as well. All
are sized and slotted to prevent that.

Of course that reply is laughable, and I believe it was meant as such.

 

[Custom Computers]

512mb in one slot doesn't make it Dual Channel, its a single channel.
It may work with the other two slots running in Dual Channel but that
doesn't mean the three are all running in Dual Channel mode.

" channel0 channel1


512MB <--- Top portion runs single channel
512MB 512MB <--- This section runs dual channel

Also, if you consider the bandwidths involved for a moment,
the AthlonXP has a 64 bit bus, operating at FSB400, for a
bandwidth of 3200MB/sec. Two sticks of PC3200 give a total
bandwidth of 6400MB/sec. That means the AthlonXP cannot
unleash the full potential of that configuration. That is
why the difference seen in real applications, between
single channel and dual channel, is as small as it is.
If I really needed the memory, I wouldn't hesitate to run
3x512MB, and ran Linux that way for a while. "

I agree with everything Paul has said here. Maybe you should read again
what Paul posted. No where does he mention the configuration your
talking about.

 

[Egil Solberg]

512mb in one slot doesn't make it Dual Channel, its a single channel.
It may work with the other two slots running in Dual Channel but that
doesn't mean the three are all running in Dual Channel mode.

You are messing things up so bad it is almost unrecoverable. You talk about
slots running in dual or single channel which makes no sense at all. I guess
you're confused from configurations for Athlon 64 or Pentium 4.
Once more: if you have populated memory slots in both channels you will run
in some kind of dual channel. If installed memory size is equal in both
channels, all memory will be accessed at full speed, this is a perfect dual
channel setup. You said that with all 3 memory slots populated, there was no
way a perfect dual channel setup could be made, but that is plain wrong. 2x
256MB in channel 1, 1x512MB in channel 2 makes all 3 slots populated and at
the same time, the amount of memory in each channel is the same. This makes
for a perfect setup where all memory is accessed at full speed resulting
from perfect dual channel operation.

" channel0 channel1


512MB <--- Top portion runs single channel
512MB 512MB <--- This section runs dual channel

Also, if you consider the bandwidths involved for a moment,
the AthlonXP has a 64 bit bus, operating at FSB400, for a
bandwidth of 3200MB/sec. Two sticks of PC3200 give a total
bandwidth of 6400MB/sec. That means the AthlonXP cannot
unleash the full potential of that configuration. That is
why the difference seen in real applications, between
single channel and dual channel, is as small as it is.
If I really needed the memory, I wouldn't hesitate to run
3x512MB, and ran Linux that way for a while. "



I agree with everything Paul has said here. Maybe you should read
again what Paul posted. No where does he mention the configuration
your talking about.

Not hard to agree with Paul, as he is perfectly right.

http://tinyurl.com/d4758

http://groups.google.ca/group/alt.c..._frm/thread/27e23db56f02cbf2/2dc03726c327f48d

Those are the links you will have to study if you're in the mood to . If
this does not explain it for you, nothing will.