Why buy ddr667+ memory if its slower than pc3200 ddr400?

Ok so I'm doing some research with memory as I need to buy some.

I've noticed a trend, as the number that refers to the --well whatever it refers to, the pc3200, pc4000, pc600 etc--as that number increases, the memory CAS speed and other timings decrease.

So..I guess I'm wondering why people buy the pc667, pc800 and pc1000 ram if it is simply slower.

So you're saying "well, so the FSB can be higher!"

except, doesn't virtually everything these days have an FSB between 133-266?

I have pc3200 memory which is rated to 200mhz--yet I noticed for example, that people who do the pentium 805d deal always use 667+ ram, except, pc3200 is completely capable of doing that, but at a 2cas latency.

So--am I totally missing something here? Are people buying slow ram at higher ddr ratings so that in the future its usable? Something else?

thanks!

E
7 answers Last reply
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  1. Yes, you're missing something.

    When you say DDR667 for a Pentium D 805, you're actually talking about DDR2 667. All current model Intel Processors take DDR2 ram not DDR1 ram. PC3200/DDR400 is DDR1 ram.

    The two types of ram fit in different slots.

    DDR2 has worse CAS latencies than DDR1. The reason we switched to DDR2 instead of staying with DDR1 is that we had pretty much reached the limit of how fast the DDR1 could go and we needed a new type of ram that was more scalable. In time DDR2 latencies will fall to the level that DDR1 is at now ( 2 - 2.5 ). Its just that DDR2 hasn't matured that far yet.
  2. So in reality you will be stuck with whatever type of ram fits in your processor/motherboard.
  3. Ah interesting.

    So the reason we're all using DDR2 is just a simple upgrade in technology..and it is slower by default.

    Yet--still I see the trend of substantially faster CAS speeds with the pc400 and lower end stuff.

    This doesn't really matter that much?

    E
  4. At the moment I think their on about an equal footing, I'd say the best DDR400 is about a match for the best DDR2 800, and I'd say that DDR2 1066 will finally conquer DDR1.

    Plus, DDR2 is faster in some things than DDR1, but DDR1 wins in games. As I understand, DDR1 is faster when there are lots of little memory requests, because that good CAS latency adds up to a lot of time saved when you are making lots of memory requests, like in games.

    DDR2 has a faster throughput, that is, if it was a sustained stream of data, it would be faster. Like Video Encoding, etc.

    But I suppose all of this is a moot point, because now both AMD and Intel use only DDR2 ram in their mainboards so u will have no choice. :?
  5. So if i bought the ASrock 775 VSTA with a conroe i'd be forced to use ddr2 even though the board has both ddr and ddr2?
  6. First of all, you're wrong. DDR2-800 CAS4 has the same real-time latency as DDR400 CAS2. The cycle time is twice as fast, so twice the cycles results in the same actual latency.

    And if you're refering to "common knowledge" you're still wrong, because common knowledge refers to older DDR2, such as DDR2-533 CAS4 and DDR2-667 CAS5. Modern DDR2 is getting numbers like DDR2-667 CAS3 and DDR2-800 CAS4, and you do the math now that you know how.
  7. Quote:
    First of all, you're wrong. DDR2-800 CAS4 has the same real-time latency as DDR400 CAS2. The cycle time is twice as fast, so twice the cycles results in the same actual latency.

    And if you're refering to "common knowledge" you're still wrong, because common knowledge refers to older DDR2, such as DDR2-533 CAS4 and DDR2-667 CAS5. Modern DDR2 is getting numbers like DDR2-667 CAS3 and DDR2-800 CAS4, and you do the math now that you know how.


    Thank you very, very much for that.

    I was a bit afraid of what I was getting myself into joining these forums when I started to look at the discussion in this thread.

    REM: CAS numbers do not reflect discrete quanitities of time on their own. CAS numbers reflect # of effective (i.e. send/receive) clock ticks.
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