About DDR2 (An old post)

THIS POST WAS SUPOSED TO BE PUBLISHED ON APRIL 5th 2005.
For some reason it wasn't so I'm posting it now...

DDR vs. DDR2 - What it means to you.

Manufacturer: Corsair

Supplied by: Corsair

by Brian Tiller (8/26/2004)



Introduction

Now that DDR2 is out, motherboard manufacturers have gotten geared up for it's appearance. Is now the time to go for the gusto and upgrade? Hopefully this article will help to shed some light on that question as we pit the new against the old.





Now, I'm not saying that the days of DDR are over, but we've pretty much seen the limits of what DDR is capable of. DDR2 is the next logical progression for memory standards and speeds. DDR2 incorporates several new designs and specifications which play a part in it's increased speed.


On-Die Termination
On-Die Termination is what it sounds like. With DDR, excess signal noise was eliminated by transistors built into the motherboard, but DDR2 has the terminating transistors built into each memory chip.


Posted CAS and Additive Latency
These two, prevent data collisions within the memory while still able to transfer more read/write instructions per clock cycle.


Off Chip Driver Calibration
Increases signal integrity


Prefetch
DDR uses a 2-bit prefetch while DDR2 now uses a 4-bit prefetch.


Package
No, not the cardboard and plastic that the memory comes shipped in, but the packaging of the memory chips themselves. Using a Fine Ball Grid Array (FBGA), DDR2 can be made smaller than DDR which uses Thin Small Outline Package (TSOP).

Below is a small chart, courtesy of Corsair, which outlines the major differences of the two types of memory.

	DDR	DDR2
Data Bus	64 bits	64bits
Data Rate	200/266/333/400 Mbps	400/533/667 Mbps
Bus Frequency	100/133/166/200 MHz	200/266/333 MHz
DRAM Frequency	100/133/166/200 MHz	100/133/166 MHz
Package Type	TSOP-II	FBGA
Densities	256MB 512MB 1GB	256MB 512MB 1GB
Voltage	2.5V	1.8V
Prefetch Size	2 bits	4 bits
Burst Length	2/4/8	4/8
CAS Latency	1.5, 2, 2.5	3+, 4, 5
Write Latency	1T	Read Latency -1

From this chart you can tell that DDR2 effectively picks up where DDR1 leaves off. It's data rate begins at 400 and scales upward to 667 currently. Another thing to take notice of are the latencies; they are double those of DDR. Apparently, they are sacrificed for the higher speed, and it should be interesting to see what kind of a trade off it is. Voltage requirements for DDR2 are greatly reduced from that of DDR. Down to 1.8 volts; this translates into a lot less power needed to read and write for the memory.


Thanks to our friends at Corsair, we are going to pit some top rated DDR and DDR2 modules up against one another and let you decide how things fare in the upgrade decision. For DDR, we have our TwinX PC3200XL modules which will be going against the new DDR2 PC5400 units.




As you can tell from the labels, what DDR2 makes up for in speed, it loses in latency timings.

We first thought of a head to head comparison for these two standards when we saw that Gigabyte had come out with a motherboard supporting both DDR and DDR2 which would make the testing as fair as possible. Using the same motherboard and chipset would prevent any outside factors from influencing the test results.

Test Setup

• Gigagbyte GA-8I915P-Duo motherboard 915 chipset


• Intel LGA 775 2.8GHz Prescott CPU


• Hitachi 80GB SATA HDD


• Lite-On DVD-Rom


• Albatron PCX5750


• Windows XP SP1

Testing

• SISoft Sandra 2004 Memory Bandwidth Benchmark


• PC Magazine Business Winstone 2004


• PC Magazine Content Creation 2004


• style="font-size:85%;">Far Cry


• Unreal Tournament 2004

We will start off with Sandra 2004's Memory Bandwidth benchmark.


Considering the differences in data rate, the results for the memory bandwidth benchmark are pretty much as expected. Now it's time to get into some productivity benchmarks with PC Magazine's Business Winstone 2004 and Content Creation 2004.




As you can see, there are some modest gains, but nothing to get excited about. The margin of difference between DDR2 and DDR here is very negligible, less than a full point in either benchmark.


One of the limitations of our motherboard is it's lack of DDR2 667 support. It will only support up to DDR2 533. We will of course be running the DDR memory at DDR400 while the PC5400 runs at DDR2 533. All other memory settings will be stock.

Overclocking

Since there is little change in performance running both the DDR and DDR2 modules at stock speeds, what kind of overclock are we going to get out of our DDR2? While we tried to overclock the DDR, we didn't get more than about 2 or 3 MHz out of it due to it's very tight timings. I would have loved to loosen the timings, but our Gigabyte motherboard (IMO - a piece of junk) had no options for the memory timings in the BIOS. However, we were able to push the DDR2 quite far and keep it stable.




We got the memory up to a whopping 607MHz which pushed our processor all the way up to 3.2GHz from it's base of 2.8GHz before the motherboard crapped out. Granted this is well below what the rated speed of the memory is, but I'm betting that once we get a better motherboard in with some serious overclocking headroom, we'll see the memory really shine.

Conclusions

When you get right down to it, for today's performance the differences between using DDR and DDR2 at 533MHz, there is little to no difference. Where DDR2 will shine, is in it's overclocking potential and the promise of future applications making use of it's enhanced speed and bandwidth. As when DDR was first introduced over SDRAM, it will be a while before these advantages are fully realized, but DDR2 will be sure to come into it's own sooner rather than later. Right now, there is no reason to upgrade your existing system based solely on DDR2. However, having said that, if you are already thinking it's time to upgrade, I would definitely recommend going with a DDR2 platform for future expandability not to mention it's overclocking potential.

We have every intention of revisiting this question in the future again once we get our hands on a better motherboard for further testing. Plus, I'm sure with a more stable board, we can reach some serious overclocks with this memory. So be sure to stay tuned in the near future for more information and articles following the progression of DDR2 and what it can mean for you.