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Help Upgrading RAM ~Comparing DDR2 and DDR3


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#1
Akimb0

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So I won a competition in PCGamer and the prize was 2GB of RAM of my choice from Crucial. My Mobo supports both DDR2 and DDR3 RAM but the memory timings on DDR3 look terrible in comparison, but I'm not sure if they can be directly compared or not.

The first RAM I considered was this:

http://www.crucial.c...L2KIT12864AL80A

# Module Size: 2GB kit (1GBx2)
# Package: Ballistix Tracer 240-pin DIMM (with LEDs)
# Feature: DDR2 PC2-6400
# Specs: DDR2 PC2-6400 • 4-4-4-12 • Unbuffered • NON-ECC • DDR2-800 • 2.0V • 128Meg x 64 •

The second was this:

http://www.crucial.c...E0E4217A5CA7304

# Module Size: 2GB
# Package: Ballistix 240-pin DIMM
# Feature: DDR3 PC3-10600
# Specs: DDR3 PC3-10600 • 6-6-6-20 • Unbuffered • NON-ECC • DDR3-1333 • 1.8V • 256Meg x 64 •


Now a few questions.

1. The fact that the DDR3 is only a single stick should make no difference at all right?
2. Which would be better for gaming?
3. Can anyone explain how DDR2 is compared to DDR3? As you can see, the memory timings on the DDR3 look terrible in comparison.

A swift reply would be most welcome, as I've had to wait nearly 2 months already just to get the "go ahead" to request my prize!

Thanks in advance to all helpful replies,

regards,

Akimb0.
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#2
SpywareDr

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Wikipedia.com > DDR3
http://en.wikipedia.org/wiki/Ddr3

Overview
...
DDR3 modules can transfer data at a rate of 800–2133 MT/s (megatransfers per second) using both rising and falling edges of a 400–1066 MHz I/O clock. The MT/s is normally twice that of MHz by double sampling, one on the rising clock edge, and the other, on the falling. In comparison, DDR2's current range of data transfer rates is 400–1066 MT/s using a 200–533 MHz I/O clock ...

Latencies

While the typical latencies for a JEDEC DDR2 device were 5-5-5-15, the standard latencies for the JEDEC DDR3 devices are 7-7-7-20 for DDR3-1066 and 7-7-7-24 for DDR3-1333.

DDR3 latencies are numerically higher because the I/O bus clock cycles by which they are measured are shorter; the actual time interval is similar to DDR2 latencies (around 10 ns). There is some improvement because DDR3 generally uses more recent manufacturing processes, but this is not directly caused by the change to DDR3.

As with earlier memory generations, faster DDR3 memory became available after the release of the initial versions. DDR3-2000 memory with 9-9-9-28 latency (9 ns) was available in time to coincide with the Intel Core i7 release.[7] CAS latency of 9 at 1000 MHz (DDR3-2000) is 9 ns, while CAS latency of 7 at 667 MHz (DDR3-1333) is 10.5 ns.

Example:

(CAS χ Frequency (MHz)) Χ 1000 = X ns

(7 χ 667) Χ 1000 = 10.4948 ns


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#3
Akimb0

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So, the DDR2:

(4/400)x1000=10ns

the DDR3:

(6/667)x1000=8.9ns

Or according to the table on wikipedia the lowest CAS 1333/10600 DDR3 has is 7...(Possibly outdated?)

So it's:

(7/667)x1000=10.49ms

Which leaves me still with the original 3 questions from my first post. This suggest the DDR3 is slower, but is it? Even if it was, would the fact that it's DDR3 still be an improvement?

Edited by Akimb0, 05 October 2010 - 08:36 AM.

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#4
Neil Jones

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Now a few questions.

1. The fact that the DDR3 is only a single stick should make no difference at all right?
2. Which would be better for gaming?
3. Can anyone explain how DDR2 is compared to DDR3? As you can see, the memory timings on the DDR3 look terrible in comparison.


1) No difference.
2) Makes no difference whatsoever. The graphics card will probably be more of a factor.
3) For most users it there is absolutely no difference between using DDR2 and DDR3 in performance terms.

Edited by Neil Jones, 05 October 2010 - 01:41 PM.

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