SDRAM vs DDR

DDR DIMMs and SO-DIMMs have the same physical dimensions as their SDRAM counterparts, but have a different footprints. DDR DIMMs have 184 pins compared to 168-pins for SDRAM DIMMs. DDR SO-DIMMs have 200 pins compared to 144 pins for SDRAM SO-DIMMs.

DDR DIMMs and SO-DIMMs also have a different notch (called 'key') that will only fit motherboards and systems especially designed for DDR. DDR modules will not fit into PC100 or PC133 sockets and are not backward compatible.

The difference between DDR and SDRAM DIMM modules is shown below.

DDR - PC1600, PC2100, PC2700 or faster		184 Pin DIMM Single Notched (or Keyed) Two operations per clock cycle
VS
168 Pin DIMM Double Notched (or Keyed) One operation per clock cycle		SDRAM - PC100 or PC133

DDR1 vs DDR2 - Perfomance Comparision

	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

There are a number of upgrades that come with the new DDR2 technology over DDR1 memory. DDR2 memory is of course faster, and will ultimately reach clock speeds of 667MHz or higher as opposed to the top functional speed of DDR1 at 400MHz. The higher speeds of DDR 2 memory allow it to have up to 10.6GB per seconds of throughput - quite a bit more than DDR1 memory which maxed at 6.4GB per second. The feature that makes these higher speeds practical is the reduced power consumption of DDR2, which runs at only 1.8 volts. Heat is one of the real banes of IC's, and the faster you try and clock a chip the hotter it runs and the less reliable it gets. One of the speed limitations of DDR1 was that at 2.5 volts created too much heat and was simply too hot to run consistently at speeds greater than 400MHz. DDR2's 1.8 volts combined with a much smaller (FBGA) chip package goes a long way towards solving the heat issue at higher speeds.

Intel Core Duo vs. Core 2 Duo: What's the Difference?

Core Duo is Intel's first dual-core CPU. It's a whole new architecture for Microsoft, using two cores on a single die, which, put simply, gives you two chips in one package. Running at lower speeds than the old Pentium line, the Core Duo conserves substantial power vs. ratcheting up clock speed while offering what was, at the time, record-breaking performance.

Now Core 2 Duo. In many ways Core 2 is the same as Core: The chips are built using the same production process and fit in the same sockets as Core Duo chips. Putting aside Core 2 Extreme (a fancy version of the Core 2 Duo), you won't see many spec changes: Both chips have the same frontside bus speed of 667MHz, but Core 2 Duo is now available at somewhat faster clock speeds . The frontside bus communicates between the CPU and RAM (and other components), and it's a notorious performance bottleneck for computers. The Core 2 also has the same L2 cache that the Core has. However, there are architecture changes to the silicon that give the Core 2 more sophisticated processing abilities. Both chips exist in desktop and laptop versions.

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