Final questions on DDR RAM?

G

Guest

Guest
I swear, these are my last questions. Thanks for the patience toward an ignorant (but humble) newbie. People have told me repeatedly that it doesn't matter if the RAM is DDR, it has to do with the processor. However, other people have told me that the motherboard has to support DDR RAM also. What are the differences between motherboards which do and don't support DDR? Second, I have learned that PC133 RAM doesn't neccesarily have to go at 133 Mhz. So, is the 133 just give an indication of the maximum bandwith (in a less obvious way than, say, PC2100 RAM)? Thanks guys. You've been a big help so far.
 

Stick_e_Mouse

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Jun 28, 2001
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Yes, a motherboard has to support DDR in order to use DDR memory (go figure). It is not backwards compatable with PC133 (a board has to have both pc133 and ddr sockets to support both kinds of memory). Those that don't support ddr support regular pc 133 (or pc100 if they are older boards). Theoretically, DDR is suppose to be a huge performance booster compared to PC133 boards/memory.

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Stick_e_Mouse

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and yes, you can underclock the pc 133 ram to 100mhz (or anywhere in between), but performace will suffer greatly.

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FatBurger

Illustrious
The 133 in PC133 is an indication of the maximum rated bus speed. Usually you can go over that, but not always. You can always go up to at least that (or get your money back).

The PC1600, PC2100, PC2400, etc. is the bandwidth. SDRAM and DDR-SDRAM has a 128 bit datapath, meaning it can move data 64 bits at a time, 133 million times a second, divided by 8 (bits to bytes) , equals 2.1GB/s, or PC2100. I hope that helps. Go <A HREF="http://forumz.tomshardware.com/modules.php?name=Forums&file=faq&notfound=1&code=1" target="_new">here</A> for my long (and probably slightly inaccurate) definition of busses.

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My Athlon can beat your Ferrari off the line.
 
G

Guest

Guest
So, even if I get an Athlon with a "200 Mhz" FSB, it'll really still only be a 100 Mhz FSB since my motherboard doesn't support DDR? Right? Please tell me I finally understand this.