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DDR vs. DDR2 - Page 2

Poll Results: DDR or DDR2?

 
  • 52% (22)
    DDR
  • 47% (20)
    DDR2
42 Total Votes  
post #11 of 26
sccr is so confused lolz, DDR2 667 operates at 333MHz end of discussion its just like DDR, you take the advertised speed and divide by 2. The only reason you could think it is any different is if you have an Asus P5 motherboard (like me) which shows the ram as 1/4th the speed so my DDR2 500 shows up as 125MHz but that's just because Asus is cooky in the head

(for those of you who are mathematically inclined you might realize that 333x2=666 not 667 but I believe its more marketing than anything, wouldnt you like to try selling devil RAM? lol actually I think thats really because it operates at 333.5 or something like that.
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post #12 of 26
yeah the 667 is because people are supersticious.
but in any case, DDR2 has a higher transfer rate, there fore it is faster to get things in and out of the RAM, thats it. im gettin 2GB DDR2 when AM2 comes out
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post #13 of 26
Quote:
Originally Posted by sccr64472
Actually, standard pc3200 DDR operates at a faster clock frequency than DDR2 667. DDR2 667 is only operating at 167 mhz, while pc3200 is operating at 200 mhz. Very common misconception.
The advantage of DDR2 over DDR SDRAM is the ability for much higher clock speeds.

A Bit of History:

With a clock frequency of 100/133 MHz, "SDR-SDRAM" transfers data on every rising edge of the clock pulse (Sin Wave Function) thus achieving an effective 100/133 MHz data transfer rate.

Unlike SDR, both DDR and DDR2 are double pumped; they transfer data on the rising and falling edge of the clock, at points of 0.0V and 2.5V (1.8V for DDR2), achieving an effective rate of 200/266/333 etc.... MHz (and a theoretical bandwidth of 1.6 GB/s .... etc) with the same clock frequency. DDR2's clock frequency is further boosted by electrical interface improvements, on-die termination, prefetch buffers and off-chip drivers. However, latency is greatly increased as a trade-off. DDR2 Prefetch buffer is 4 bits wide, whereas DDR is 2 bits wide & DDR3 is 8 bits wide.

Power savings are achieved primarily due to an improved manufacture process, resulting in a drop in operating voltage (1.8 V compared to DDR's 2.5 V). The lower memory clock frequency could also help — DDR2 can use a real clock frequency 1/2 that of SDRAM whilst maintaining the same bandwidth).

Chips
  • DDR2-400: DDR-SDRAM memory chips specified to run at 100 MHz, I/O clock at 200 MHz
  • DDR2-533: DDR-SDRAM memory chips specified to run at 133 MHz, I/O clock at 266 MHz
  • DDR2-667: DDR-SDRAM memory chips specified to run at 166 MHz, I/O clock at 333 MHz
  • DDR2-800: DDR-SDRAM memory chips specified to run at 200 MHz, I/O clock at 400 MHz
  • DDR2-1000: DDR-SDRAM memory chips specified to run at 250 MHz, I/O clock at 425 MHz.

Sticks/Modules
  • PC2-3200: DDR2-SDRAM memory stick specified to run at 200 MHz using DDR2-400 chips, 3.200 GB/s bandwidth
  • PC2-4200: DDR2-SDRAM memory stick specified to run at 266 MHz using DDR2-533 chips, 4.267 GB/s bandwidth
  • PC2-5300: DDR2-SDRAM memory stick specified to run at 333 MHz using DDR2-667 chips, 5.333 GB/s bandwidth
  • PC2-6400: DDR2-SDRAM memory stick specified to run at 400 MHz using DDR2-800 chips, 6.400 GB/s bandwidth

Moving on to the Future:

DDR III

DDR III is likely to be called DDR III SDRAM (Double Data Rate Three Synchronous Dynamic Random Access Memory), is the name of the new DDR memory standard that is being developed as the successor to DDR2 SDRAM.

The memory comes with a promise of a power consumption reduction of 40% compared to current commercial DDR2 modules, due to DDR III's 90 nanometer fabrication technology, allowing for lower operating currents and voltages (1.5V, compared to DDR2's 1.8V or DDR's 2.5V). "Dual-gate" transistors will be used to reduce leakage current.

DDR3 Prefetch Buffer width is 8 bit, whereas DDR2 is 4 bit, and DDR is 2 bit.

Theoretically, these modules could transfer data at the effective clockrate of 400-800 MHz (for a bandwidth of 800-1600 Mb/s), compared to DDR2's current range of 200-533 MHz (400-1066 Mb/s) or DDR's range of 100-300 MHz (200-600 Mb/s). To date, such bandwidth requirements have been mainly on the graphics market, where vast transfer of information between framebuffers is required.

Prototypes were announced in early 2005, while DDR3 specification is expected to be publicly available in mid 2006. Supposedly, Intel has preliminarily announced that they expect to be able to offer support for it near the end of 2007. AMD's roadmap indicates their own adoption of DDR3 to come in 2008.

Spec standards (not finalized yet)

Chips
  • DDR3-800 : DDR-SDRAM memory chips specified to run at 100 MHz, I/O clock at 400 MHz
  • DDR3-1067: DDR-SDRAM memory chips specified to run at 133 MHz, I/O clock at 533 MHz


Sticks/Modules
  • PC3-6400: DDR3-SDRAM memory stick specified to run at 400 MHz using DDR3-800 chips, 6.40 GB/s bandwidth
  • PC3-8500: DDR3-SDRAM memory stick specified to run at 533 MHz using DDR3-1067 chips, 8.53 GB/s bandwidt

Thus sccr64472 is correct. The error lies in seeing the quad pumped rise and fall multiplied frequency as the actualized frequency when it is not.

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post #14 of 26
so what about RDRAM, that runs at 800MHZ, whats the transfer rate for that?
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post #15 of 26
RAMBUS is Quad Data Rate, so the actual speed was 100mhz for PC-800 16-bit but operated at a maximum of 400mhz. Just like PC-1066 it operates at 533mhz for 32-bit.

I like the RAMBUS days better than DDR. CPU's with a 400mhz fsb operated hand-in-hand with PC-800 it was a TRUE 1:1 ratio and also the 3.06ghz HT which was a 533mhz fsb, it was great with PC-1066, again; a TRUE 1:1 ratio.

All in the good old days of the 850 and 850E.

I feel with DDR2 like in the RAMBUS days, a good CPU/RAM 1:1 ratio. With DDR it felt for me more like a 4:3 an 5:4 all the time, even though it showed a 1:1, but that's just me.
post #16 of 26
DRR2 only if its DDR2 800, 600 is really no big upgrade from DDR, but DDR2 800 blows away any DDR....
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post #17 of 26
Thread Starter 
Keep in mind this is a VALUE RAM discussion.
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post #18 of 26
Even talking about value ram, I like DDR2. Regular DDR won't be around that much longer.
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post #19 of 26
Quote:
Originally Posted by klewiss
Keep in mind this is a VALUE RAM discussion.
Keeping that in mind, there is no doubt that value ram will easily make the 700MHz bus. I have experimented with Corsair Value, Samsung Value and *gasp* Kingmax Value DDR2 PC4300 Dram with all of them making the 711MHz of my 1066fsb Pentium 4 630 3.0GHz @ 4.02Ghz and this is at 2.05V with 3-3-3-10 which translates to 2-2-2-5 on a single strobe.

Thus even value DDR2 Dram is a fair value considering what one has to spend for 2-2-2-5 DDR Ram. The real main difference between DDR and DDR2 in terms of performance is that DDR always has a write latency of 1T. This time is dictated by the JEDEC specification and cannot be changed. For DDR2, this write latency depends on the read latency and equals write latency minus one clock. In comparison to 1 clock for DDR this is a lacking feature and is at this time the most basic drawback to DDR2, especially so with an AMD processor in which the control is strapped back to the onboard memory controller at such a low speed (in comparison to the read latency of that controller) thus creating a read/write stall.

Those who think AM2's implimentation of DDR2 will be a great factor will find this not to be the case in my opinion and the main reasons for AMD's implimentation of DDR2 is two-fold. One is to appease the DRAM manufacturers and the other is to keep up with Intel's newer technology. They have it so we must thinking does not always translate to performance necessary implimentations.

Edit: Changed Timings (3-3-3-9) and the vdimm to 2.1V

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post #20 of 26
thx Ropey, great info

so should i wait for the mb that supports DDR2 for AMD64, or not?
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