¿ DDR SDRAM SDR ?

[DPA]

i love this boast i have heard, its great

"hey, i have 128MB of Sync...D...RAM!"

you've got E-Machines to thank for that one, how about SDRAM anyone? SDR is probably coined from the Video card market right after the creation of DDR, so it would clear up any questions about which was faster.

Ive got it, ill make a suggestion to e-machines to change their onboard AGP to AG processor Video Adapter, that way, more people can sound cool about their computers, and surf the net in ignorance

*and post up on techtv.com*

| what??? where did that come from iNEB?
V

i believe everyone is aware of DDR and standard SDRAM

Double Data Rate Synchronous Dynamic Random Access Memory

aaannnnd SDR was just short for SDRAM

[iNeb]

We know, but there is SDRAM, and DDR SDRAM

[Etruscan]

Uh, Wizzard, if your out there, what's the difference in the way Double Data Rate RAM works from Single Data Rate?

For instance, when using SDRAM on an AMD board at 133mhz, it was my understanding that the 'data rate' was 266 because the socket A standard is to send 2bits of infomation per cycle. How does Double Data Rate improve on this performance?

[snookay]

ddr sends stuff the speed x2 of sdram. nuff said. unless im wrong which i dont think

[Wizzard~Of~Ozz]

DDR uses the leading and falling edge of a clock cycle, A clock is a square wave, So it goes

+voltage 0 +voltage 0......

SDR transfers on the + voltage, DDR transfers when the voltage goes up to +voltage and when it goes to 0, allowing double the transfers per clock cycle.

I'm not going to go into Rambus Memory since it's a completely different technology, And SGRam hasn't been used in a long time, but I believe it's Synchronus Graphics Memory, This was a more expensive faster memory then the current 60ns an 50ns memory That was availible at the time (Memory used to run much slower, But back then it was EDO or Fastpage but those haven't been used since 486/Pentiums. some modules ran at 100ns)

So DDR is not twice the speed, however it is as effective as double the speed. Marketing departments are the ones that do a lot of this

330MhzDDR (660Mhz)

Which means they suck at electronics and don't understand the technology, but in the Marketing department it's all about selling product, even if you have to mutilate a technology.

Also, SDram and Dram are different modules, But from what I remember the difference is mainly voltage, Dram was at 5v, SDram is at 3.3. Dram was also Fastpagemode and Did NOT usually run at the same clock speed as the processorFSB (P166MMX @ 66Mhz FSB with 25Mhz Memory.)

Dram was common in Pentium systems since it meant you could put 1 module in in place of 2 72 pin Simms (Single In-line Memory Module)

SDR SDRam chokes an Athlon System, The processor can send information to the northbridge at 133Mhz DDR, from there if it's memory intensive it can send the data at 133Mhz DDR to memory modules, however if you are only running SDR, then the processor sits idle 1/2 the time while waiting for memory to be written (since data transfer is 133DDR (266Mbits/S) to NB, then NB -> memory is only 133Mhz (133Mbits/sec)

SDR is very horrible for Athlon Systems. it strangles the processor.

[Etruscan]

Thanks Wizzard. I see: the memory bus is only 133 with SDRAM. I thought the whole system was 'double pumped'. I guess I was mistaken. It was my impression that the improvements with DDR at 266 were achieved by a wider bus on DDR boards, thus improving band width. I guess I'll have to read up.

[nukes]

then the processor sits idle 1/2 the time while waiting for memory to be written (since data transfer is 133DDR (266Mbits/S)

Not quite true as that's what the cache is there for. Also, the bandwidth is much higher than that. If you assume DDR is twice as fast as SDRAM, you get around 1.3gb/s at 133mhz, and 2.7gb/s at DDR266.
But you are right in that it can be a bottleneck in new Athlon systems, and is essentially a legacy device
That said I have just bought 512mb PC133 ram for my new computer as there is no way I can afford 512mb of DDR, and I would prefer to have 512mb PC133 than 256mb DDR