如果只是以 CPU-北橋 的頻寬小於 北橋-記憶體 這點就斷言nforce2的雙通道沒有用處的話,有點太過武斷了....

以下節錄一段nforce2 DualDDR Memory Controller的資料
1.In 128-bit mode, both of the two independent 64-bit memory controllers
. Three separate address buses
. Two separate data buses
2.In 64-bit mode one DIMM can be located on either of the two independent
64-bit memory controller buses
3.First DIMM on memory controller A
4.Second and third DIMMs on memory controller B
Each independent 64-bit memory controller accesses 128-bits of data on
each memory clock period, delivering a bandwidth of 6.25 GBps.

More than just a single “128-bit” memory controller, DualDDR consists
of two independent, complementary, and intelligent memory controllers.

Both memory controllers operate concurrently to each other to “hide”
latencies associated with typical chipsets”.

For example, controller “A” reads or writes to main memory while the
controller “B” prepares for the next access, and vice versa.

The complementary nature of the two memory controllers cuts the effective
latency in half. Equally important is the second-generation dynamic
adaptive speculative pre-processor (DASP)), which has been re-architect
with a more aggressive algorithm. Write buffers and draining algorithms
has also been re-architected to reduce latency.

With DualDDR's lower latency, users get a system that is better suited
to multi-tasking.



如果是像在P4上面的DualChannel DDRSDRAM的話
那麼實作在K7上面是真的會如前面所說,沒有太大的用處
但是,nforce/nforce2的雙通道的技術卻不是只有這個樣子
否則,也不會在大部分的測試下,雙通道會比單通道有著更高的效能了

首先,nforce/nforce2是有兩組獨立64bit的memory controller
這跟一般在P4晶片組上面的雙通道有什麼不同呢?
在P4的雙通道晶片組上面,要構成雙通道的話
就要使用兩條同樣容量,而且最好是同樣顆粒的ram
在跑雙通道時,其實相當於一個128bit的通道,只有一組controller

但是在nforce/nforce2上呢?
是用兩組獨立的64bit memory controller
甚至可以做到一組在做寫入,另外一組在做讀取
跟nvidia在Geforce3(NV20)上的LMA技術概念上有一部分是相通的
而nvidia有這部分的技術,用在nforce2上也是很正常的
因為有兩組controller,所以nforce/nforce2可以在插3條ram
而且容量都不一樣的狀況下也可以啟用雙通道
這也是一般P4的雙通道晶片做不到的

不過,當初nforce/nforce2會做雙通道的最主要原因,主要也還是為了內建顯示的頻寬需求吧,差了這一半的頻寬對nforce2 IGP有什麼影響呢?
看一下各家所做的測試應該就很清楚了,在3D效能上,跑雙通道的nforce2 IGP遠超過只有單通道的狀況
至於在nforce2 SPP的話,這麼多的測試也讓大家有個答案了
效能有增加,但是增加有限
這大部分還是限於CPU-北橋 的頻寬小於 北橋-記憶體
沒辦法有如P4那般,在雙通道的晶片組上效能大增
但是,要說nforce/nforce2的雙通道完全沒用,那麼就有點小看了nforce2的設計了

ps:熬夜熬過頭了,有點頭昏,如果有想到別的,之後再補上