200MHz FSB vs. DDR

Flyboy

Distinguished
Dec 31, 2007
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My motherboard (K7M) says that is supports a 200MHz FSB. Now, I thought this meant that by bus runs at 100MHz, but with data being transferred on BOTH clock edges. If this is true, then what the hell is the difference between my board and the new DDR boards? I asked a salesman this and he nor the other three employees could explain it. I'm preparing to build my brother a system and want to get this fact straight.

I know this is probably a dumb question...but I figure it only requires a short explanation. ;)

Thanks.
 

Grizely1

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Dec 31, 2007
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First, the DDR Memory is different than the normal memory. We refer to them as "DDR Boards" because they support DDR Memory (200 or 266 FSB). The DDR memory is 184 pin (i think) instead of 168 (SDRAM). It's interfaced differently. You can't stick DDR memory into your SDRAM motherboard.

Also the DDR Mobos have 200 <b>or</b> 266MHz FSB.

All Athlon motherboards are 200MHz FSB.
 
G

Guest

Guest
Ok, I could be completely wrong about this, I'm no expert, but I'm going to give it a shot.

The way I understand it is, the motherboard chipset talks to the CPU at 200mhz. That 200mhz is a combination of the memory's 100mhz and various other components of the motherboard talking to the chipset.

While DDR motherboards have the 266mhz bus from the chipset to the CPU, they also have 266mhz bus from the memory to the chipset. So, it seems that the DDR boards have the ability to use up all of the available bandwidth between chipset and CPU more often than the older boards.
 
G

Guest

Guest
i think that the fsb of all althon/tbird/duron runs at 100mhz ddr'd up to 200mhz equivalent and the old mobos run their mem at 100mhz, the new mobos run their mem ddr'd as well so you have a 200mhz effective mem speed
 

mpjesse

Splendid
OK- this will be easy to interpret. The "double pumped" bus of the Athlon runs at 200mhz (PR) rating. It actually runs at 100mhz (clock) Just like DDR memory, data is transmited on the rise and fall of the clock cycle. So, DDR memory is nothing more than "double pumped" memory actually running at 133mhz/100mhz. All DDR really does is increase bandwidth- not clock speed (which are 2 totally different things). Look at any benchmarks of DDR memory and you'll see performance gains mainly bandwidth. But, as seen in Rambus/P4 combinations- bandwidth will only go so far until a higher clock speed can be implemented. In other words, you can have a ton of bandwidth- but if you don't have speed (clock), it's not going to get any faster.

Compare it to a car- supe up nothing but the engine- all you really have is a fast engine- not car. Supe up the transmission and rear end (leave the engine alone) all you really have is the potential for a fast car. The engine is the speed/CPU and the transmission/rear end is the bandwidth.

Right now, bandwidth is what CPU's need- not faster clock speeds of memory. Soon, after everyone stops tripping on the amazing bandwidth of DDR- clock speed in memory will ramp up to 200mhz.

-MP Jesse