Help! Confused with Athlon memory...

[Arbiter]

In the market for a new Athlon PC, and I'm sorely confused regarding the differences between PC100, PC133, DDR1600 and DDR2100 memory and the chipsets that support them.

KT-133A supports a 133MHz FSB with data clocked at twice that, 266Mhz, right? So, with that chipset, does PC133 memory successfully double-clock to 266MHz? Or 133? Then what is the difference between that and DDR SDRAM and the DDR chipsets?

If you have a KT-133 mobo, which as I understand it doesn't quite support 133 but does do 100, and use PC133 memory, is the fastest it will clock the data at 200MHz? Or 133? So there'd be no reason _speed-wise_ to buy PC133 over PC100 in that case?

I guess the primary problem I have is reconciling the difference between Athlon's 'double-clocked bus' with PC100/PC133 (=200/266MHz = 1600/2100Gbps), and the difference between that and DDR SDRAM (= 1600/2100 Gbps). Seem the same to me, I know they're not, what am I missing?

Thanks!

 

[Taplight]

Arbiter,

The KT133 chipset supports the 100mhz ddr front side bus for the cpu but the memory controller is clocked at either 100mhz or 133mhz period. The memory is not double pumped. Neither is it for the KT133a. The 133a just gives the option of running a 133mhz ddr fsb cpu but still leaves the memory at 133mhz. The DDR boards give you the double pumped memory. Seems you already know that the double pumped pc100 memory is called DDR1600 and the same for the double pumped pc133 which is called DDR 2100 which refer to their respective bandwidths and not their mhz like the old ones are(seems like more of a marketing gimmick to me). Bottom line is that all the aforementioned boards support a ddr cpu fsb but only the DDR RAM boards support double pumped ram. Hope that helps.

Taplight

 

[Mem]

<< So there'd be no reason _speed-wise_ to buy PC133 over PC100 in that case? >>



Yes there is because when you run the memory at 133mhz it uses the extra 33mhz over the 100mhz ram for memory bandwidth ,if you look at any benchmarks you will see a slight speed increase over the standard 100mhz ram with 133mhz ram being used.

 

[i8mywindpipe]

&quot;Double Pumped&quot;
Hehehe

 

[Arbiter]

Thanks for the explanation guys!

> Bottom line is that all the aforementioned boards support a
> ddr cpu fsb but only the DDR RAM boards support double pumped ram.

What's the advantage to a DDR CPU FSB, when the memory itself is not DDR? Isn't it just a marketing phrase, until they get DDR memory to match? That's probably what's confused me most; a lot of the PC houses out there are touting Athlon's 'DDR' FSB and imply that (on their KT133 sol'ns) the PC100/PC133 memory is also being double-clocked.

My dilemma is whether or not to wait for the DDR chipsets, or go with the current memory implementations. I want a computer that'll last 4 years like my last one, but I don't want to be an early adopter of a mobo that goes the way the 810 did...

 

[Mem]

Arbiter read these links http://www1.anandtech.com/showdoc.html?i=1344 &amp; http://www1.anandtech.com/showdoc.html?i=1386 this goes into detail of memory etc.

 

[Arbiter]

Thanks man, I somehow missed that second link in my prior research-a-thon, that one's a big help.