Memory types?

[WoL-Shiver]

hi guys, im just wondering about the difference in ddr2 memories.

 

kinda like TCCD/VX etc etc when it comes to DDR. i hacvent heard ,uch about the ddr2 memory types, except the name alone micron D's.

 

any info would be great.

 

thanks, WoL

[Sharp]

Hello,

 

Because DDR2 is sort of recent there has not been many chips.

 

Micron

Elpida

Samsung

Hynix

Infineon

 

All of these manufacturers have some DDR2 IC's.

 

The Micron and Elipda ones clock very well, both are rated 800Mhz 4-4-4-12.

 

The Micron ones and some Elpida chips can clock to near 1000Mhz.

Timings will need to be increased, 5-5-5-15.

 

And what is DDR2?

 

Memory data store in the actual chip (array) always gets sent to an Input/Output buffer.

On DDR1 the data width from Memory array to Buffer = 2 bits wide.

 

So you end up with,

 

- 1 data transfer on the rising edge of every cycle.

- 1 data transfer on the falling edge of every cycle.

 

 

With DDR2, the data bus from Memory to the Input/Output buffer is 4 bits wide.

Therefore you end up with 2 extra data transfers.

 

- 2 data transfer on the rising edge of every cycle.

- 2 data transfer on the falling edge of every cycle.

 

Which means the performance has been doubled.

 

- 200Mhz with DDR1 = equivalent to 400Mhz

 

- 100Mhz with DDR2 = equivalent to 400Mhz

 

 

PC2-3200 400Mhz actual memory frequency = 100Mhz

PC2-4200 533Mhz actual memory frequency = 133Mhz

PC2-5400 667Mhz actual memory frequency = 166Mhz

PC2-6400 800Mhz actual memory frequency = 200Mhz

 

DDR2 is also shown as PC2-XXXX

eg, PC2-6400

 

There are a few more changes which would explain why PC2-3200 is slower than PC3200.

[WoL-Shiver]

thanks sharpy. i knew the about the data rates already but thanks for the in depth. youve elft me wondering why pc23200 is slower then pc3200, im assuming ddr 2 can do the same timings at an even lower voltage, no?

 

also, i knew already of those manufacturers, but who makesd what? in the sense of, well. ocz's plate rev 2 ddr 400 was tccd, but ocz's gold ddr 500 was VX (?)?

 

are we starting to see differances in DDR2 ranges? or only manufacturer based?

[Sharp]

When DDR2 first came out the chips were really slow (in terms of latency/timings).

 

So no they do not do the same timings.

For example,

http://www.pcstats.com/articleview.cfm?articleID=1672

 

Look at this old DDR2 PC2-4200 kit.

266Mhz 4-4-4-12

 

And compared to a DDR1 1GB kit,

GEIL one TCCD 2x1GB PC4800

300Mhz 2.5-4-4-7

 

See how low the timings are on the DDR1 kit.

Which means it performs a lot better.

 

But now DDR2 chips have improved.

PC6400 = 400Mhz @ 4-4-4-12, compared to the old PC2-4200 its a lot faster.

 

VX was UTT CH5.

Still very little differences between DDR2 kits.

[ooeric]

some ddr2 modules can run pc2 6400. ddr2 800. at cas 3. lol

 

my ram can run ddr1100 at 4-4-4-4. very big difference in ddr2 overclocking

 

because every D9 ic is different. you can say strange in some sense.

[Yellowbeard]

Promos is turning out a decent IC also. Pretty much everyone except Crucial, (owned by Micron) is using a Promos IC for 1 offering of their mid level PC6400 parts.