On 12 Jun, 14:14, "GT" <ContactGT_remo...@hotmail.com> wrote:
> <jameshanle...@yahoo.co.uk> wrote in message
>
> news:1181652420.577218.145210@a26g2000pre.googlegr oups.com...
>
> >I know a bit about what DDR2 is.. and different notch position, not
> > compatible with DDR.
> > But i'm puzzled over PC2.
>
> > I once suspected that PC2 was DDR2.
> > I'm sure i've often seen PC2 DDR2
>
> > But I just saw some RAM in a laptop that said PC2 but also said DDR.
>
> I suspect you have seen something like PC2700 and assumed it is PC2 700,
> whereas it is actually PC 2700.

absolutely right!!
thanks!

I shouldn't have made that mistake. It said PC2100. DDR 266 (so
133Mhz).
133*16~=2100.

But since it said DDR, it had to be PC. Not PC2

I goess there is no such thing as PC2 100

I'm not up on PC2 speeds.. But I know that with PC amounts, they went
PC 66, PC 100, maybe even PC133 and PC150 (for the bus), Then they
came up with DDR. What was the lowest speed they made DDR at ?

With DDR, PC became redefined, to be followed by bandwidth amount
(actual bus speed * 16). And in the DDR notation, (DDR 266, - noting
that one doesn't write Mhz after effective speed..)

It was PC 2100, 'cos DDR 266. (actual speed 133Mhz, effective speed
266). 133*16~=2100

What are the ranges of PC2 numbers? I guess they don't start as low as
100.


I remember the the EDO RAM with no clock, speed measured in
nanoseconds. In the days of the P120. (for those that don't recall.
Pentium 1, 120MHz !).

Was that EDO RAM immediately followed by SDRAM . Such as PC 66.






> I shall explain...
>
> DDR stands for Double Data Rate. DDR2 is Double Data Rate (2x). EG "DDR
> 266", "DDR 333", "DDR2 553" etc.
>
> A 'PC' rating is also a measure of speed of memory - PC 2700, PC 3500 etc.
>
> With DDR, the number following DDR or DDR2 is a measure of speed of a memory
> chip in ticks per second. It is the quantity of transfers the memory is
> capable of per second. DDR333 runs at 166MHz and does 2 transfers per
> second, therefore the number is 2x166=333. DDR2 533 runs at 133 MHz and does
> 4 transfers per second so number is 4x133 = 533.
>
> With the PC rating, the number is the amount of MegaBytes the memory can
> transfer in a second. PC 2700 can transfer 2700MB/s
>
> PC2100: 266Mhz
> PC2700: 333Mhz
> PC3200: 400Mhz
> PC3500: 433Mhz
> PC3700: 466Mhz
> PC4000: 500Mhz
> PC4200: 533Mhz
>
> Hope that clears thing up
> GT

thanks, I knew most of that, about DDR, though not at the top of my
head. I didn't know much about DDR2, but you've filled me in. it's
times 4.. I recall reading it sent once during the rise and once
during the fall of the FSB's clock's signal, as well as the peek and
the trough of the wave. So 4 times in a clock cycle.

(peak and trough of wave, being, high school physics terminology!)