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- Dec 2, 2002
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- Tucson, Arizona
Ok well theres been a lot of questions on what dual channel is/does. So im goiing to put all the questions ive seen on dual channel that have been answered on this one post.
PLEASE CORRECT IF ANY OF THIS IS WRONG. ALSO, PLEASE ADD ON TO THIS.
Heres a quick explanation on how dual channel affects AMD and p4 in general.
Dual channel modes run two (hopefully identical) sticks of ram in parallel, theoretically doubling bandwidth. The reality is that bandwidth does not nearly double, with something more like 60% greater bandwidth realized compared to an otherwise similar single channel configuration.
Dual channel does not improve latency, rather the opposite. In most cases dual channel configurations will exhibit worse latency than otherwise similar single channel configurations. This is where the general statements stop, the rest is different between the Intel 865/875 and AMD Nforce2 platforms.
In regards to performance AMD's largely do not benefit from dual channel because of the Athlon XP's system architecture, not that the cpu itself "lacks bandwidth". The reason for this factor is that the front side bus is double pumped, meaning the connection between the cpu and the rest of system is not sized large enough to benefit from the increased memory bandwidth. For the purposes of this discussion we can treat the fsb as existing to link the cpu and the memory. Placing more memory bandwidth at the memory end of the link isn't very productive since it exceeds the ability of the fsb to accomodate the increased bandwidth.
P4's on the other hand have a quad pumped fsb. This gives them roughly twice the fsb bandwidth of AthlonXP's at a given fsb clock rate. This means they are in an excellent position to take advantege of the roughly 60% greater bandwidth dual channel configurations provide.
AMD and Intel also differ in the latency department. Nforce2's dual channel setup, being somewhat primitive compared to Intel's, can do nothing but harm latency as compared to single channel configurations. Intel created the PAT (performance acceleration technology) to counter this effect. PAT is a chipset level optimization that effects both the latency of the memory controller and enforces faster memory chip timing values. These advantages allow Intel dual channel configurations to have equal or better latency than single channel modes.
The two platforms also differ in the number of dimms supported. Only Nforce2 allows you to add a third dimm and retain dual channel operation. Intel systems must use either 2 or 4 identical dimms for dual channel operation.
As far your last point, I simply don't understand what you are getting at. If you need 1GB, you need 1GB. Whether or not you are running dual channel does not effect this. And conversely, if your applications and usage work fine on 512MB, again, whether or not you running dual channel does not factor into this.
Q) If i have 1-512 stick and 1-256 stick but the both have the same bus, will it work fine?
A)No, the two sticks ram must be the same.
Q) What is the performance boost?
A)AMD does not get much improvement from dual channel because the bandwidth of an XP300+ Barton is exactly the same as the bandwidth of a single stick of PC3200 RAM. The Nforce2 chipset also isn't terribly efficient in terms of bandwith. If you run 2 sticks at 100MHz, you get only a little over one stick. It's apperarntly designed with other things in mind.
On the P4 systems the boost is more noticable, its ~60%-80%.
Q) If I use dual channel and then later on decide to put a third stick of memory in, will having 3 RAM modules negate the dual channel effect?
A)It would only negate the dual channel effect if y ou have a p4 system, not on AMD thou.
Q)Would 1gb be better then 512 dual channel?
A)No, dual channel is better because you would be getting more bandwidth....right?
Q) Is dual channel mode best for performance and OC?
A)Running your RAM in Dual Channel will increase preformance slightly, but may restrict your overclock speeds.
ok this is all i came up with for now..but i only got to page 2 of the search page..more to come.
agian, please correct me if i am wrong, please add on to this.
PLEASE CORRECT IF ANY OF THIS IS WRONG. ALSO, PLEASE ADD ON TO THIS.
Heres a quick explanation on how dual channel affects AMD and p4 in general.
Dual channel modes run two (hopefully identical) sticks of ram in parallel, theoretically doubling bandwidth. The reality is that bandwidth does not nearly double, with something more like 60% greater bandwidth realized compared to an otherwise similar single channel configuration.
Dual channel does not improve latency, rather the opposite. In most cases dual channel configurations will exhibit worse latency than otherwise similar single channel configurations. This is where the general statements stop, the rest is different between the Intel 865/875 and AMD Nforce2 platforms.
In regards to performance AMD's largely do not benefit from dual channel because of the Athlon XP's system architecture, not that the cpu itself "lacks bandwidth". The reason for this factor is that the front side bus is double pumped, meaning the connection between the cpu and the rest of system is not sized large enough to benefit from the increased memory bandwidth. For the purposes of this discussion we can treat the fsb as existing to link the cpu and the memory. Placing more memory bandwidth at the memory end of the link isn't very productive since it exceeds the ability of the fsb to accomodate the increased bandwidth.
P4's on the other hand have a quad pumped fsb. This gives them roughly twice the fsb bandwidth of AthlonXP's at a given fsb clock rate. This means they are in an excellent position to take advantege of the roughly 60% greater bandwidth dual channel configurations provide.
AMD and Intel also differ in the latency department. Nforce2's dual channel setup, being somewhat primitive compared to Intel's, can do nothing but harm latency as compared to single channel configurations. Intel created the PAT (performance acceleration technology) to counter this effect. PAT is a chipset level optimization that effects both the latency of the memory controller and enforces faster memory chip timing values. These advantages allow Intel dual channel configurations to have equal or better latency than single channel modes.
The two platforms also differ in the number of dimms supported. Only Nforce2 allows you to add a third dimm and retain dual channel operation. Intel systems must use either 2 or 4 identical dimms for dual channel operation.
As far your last point, I simply don't understand what you are getting at. If you need 1GB, you need 1GB. Whether or not you are running dual channel does not effect this. And conversely, if your applications and usage work fine on 512MB, again, whether or not you running dual channel does not factor into this.
Q) If i have 1-512 stick and 1-256 stick but the both have the same bus, will it work fine?
A)No, the two sticks ram must be the same.
Q) What is the performance boost?
A)AMD does not get much improvement from dual channel because the bandwidth of an XP300+ Barton is exactly the same as the bandwidth of a single stick of PC3200 RAM. The Nforce2 chipset also isn't terribly efficient in terms of bandwith. If you run 2 sticks at 100MHz, you get only a little over one stick. It's apperarntly designed with other things in mind.
On the P4 systems the boost is more noticable, its ~60%-80%.
Q) If I use dual channel and then later on decide to put a third stick of memory in, will having 3 RAM modules negate the dual channel effect?
A)It would only negate the dual channel effect if y ou have a p4 system, not on AMD thou.
Q)Would 1gb be better then 512 dual channel?
A)No, dual channel is better because you would be getting more bandwidth....right?
Q) Is dual channel mode best for performance and OC?
A)Running your RAM in Dual Channel will increase preformance slightly, but may restrict your overclock speeds.
ok this is all i came up with for now..but i only got to page 2 of the search page..more to come.
agian, please correct me if i am wrong, please add on to this.
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