DDR Dual Channel vs. DDR2

[murgaan]

Consider an Intel Processor (630) with an 800MHz FSB and the following
memory configurations. Assume 1GB total:

2 sticks DDR 400MHz (dual channel)
1 stick DDR2 800Mhz
2 sticks DDR2 800Mhz (dual channel)

Is the DDR 400MHz configuration using the 800MHz front side bus to its
maximum potential, or is the single channel DDR2 case faster. If so,
why?

Does DDR2 800Mhz running dual channel provide twice the bandwidth
(1.6GHz)? If so, is it wasted since the FSB is 800Mhz?

Thanks

 

[kony]

Consider an Intel Processor (630) with an 800MHz FSB and the following
memory configurations. Assume 1GB total:

2 sticks DDR 400MHz (dual channel)
1 stick DDR2 800Mhz
2 sticks DDR2 800Mhz (dual channel)

Is the DDR 400MHz configuration using the 800MHz front side bus to its
maximum potential,
Usually

or is the single channel DDR2 case faster. If so,
why?
No.


Does DDR2 800Mhz running dual channel provide twice the bandwidth
(1.6GHz)?

Twice as much as which alternative?
Generally, no. Beyond a certain point the theoretical
bandwidth doesn't matter because it's not being continually
used, is not the primary bottleneck.

If so, is it wasted since the FSB is 800Mhz?

No, FSB is quad-data-rate, not double data rate.

To put it simply- dual channel is worthwhile for a minor
performance gain. Whether DDR(1) or DDR2, depends on the
quality of memory you buy, DDR2 has higher latency so if you
buy good memory it can be faster than DDR1. If you just
accept whatever low-end memory an OEM puts in a system but
don't know it's latency specs, it might be faster or might
be slightly slower. Don't expect high-end memory from an
OEM, if you want ultimate memory performance you will need
to hand-pick your own DDR2 memory and pay a near-premium for
it.

 

[bgd]

Consider an Intel Processor (630) with an 800MHz FSB and the following
memory configurations. Assume 1GB total:

2 sticks DDR 400MHz (dual channel)
1 stick DDR2 800Mhz
2 sticks DDR2 800Mhz (dual channel)

Is the DDR 400MHz configuration using the 800MHz front side bus to its
maximum potential, or is the single channel DDR2 case faster. If so,
why?

Does DDR2 800Mhz running dual channel provide twice the bandwidth
(1.6GHz)? If so, is it wasted since the FSB is 800Mhz?

Thanks

it is actaully a 200 FSB for the 800 fsb and ddr 400 , its a synchronous
thread gain.
Performance would be gained with the threads, unless fsb > 200 ,then it is
the real improvement.
width of work is the thread increase, actual root of fsb is the real speed.

 

[murgaan]

It has come to my attention that there are no Northbridges that even
support DDR2-800. The highest supported seems to be 667MHz. Since the
Intel 630's FSB is 200Mhz (800), it seems to me that low latency DDR400
will be the better performer, No?

 

[Paul]

It has come to my attention that there are no Northbridges that even
support DDR2-800. The highest supported seems to be 667MHz. Since the
Intel 630's FSB is 200Mhz (800), it seems to me that low latency DDR400
will be the better performer, No?

DDR2-533 surpasses DDR400 in benchmarks. It was DDR2-400 which
was slower than DDR400.

For "native DDR2-800" support, try this product with a 975X chips.
There may be others - this is the first one I found.

P5WD2-E Premium
http://www.asus.com/products4.aspx?modelmenu=2&model=981&l1=3&l2=11&l3=248

Intel doesn't mention this "native" support. It could be that
DDR2-800 is not a JEDEC spec point, so Intel ignores anything
which is not JEDEC approved. But that doesn't stop Intel from
putting undocumented dividers in the chipsets, that allow stuff
like that to be achieved. Search for "667" in here, to find
references to the official DDR2-533 or DDR2-667 support.

http://download.intel.com/design/chipsets/datashts/31015801.pdf

This is the JEDEC doc I found the last time I looked. On PDF
page 70, you can see that DDR2-800 is part of the standard,
so no excuse for Intel not to include it.

http://www.jedec.org/download/search/JESD79-2B.pdf

Just one of those grey areas I guess. The constant battle
between the motherboard manufacturers and Intel, to add
features to attract customers...

HTH,
Paul