SDRAM & DDRAM

For more info, see:

http://www.crucial.com/library/index.asp

some more information:
http://www.kwan.ca/review/hardware/SDRAMvsDDR/SDRAMvsDDR.html
http://www.lostcircuits.com/motherboard/asus_a7v133/9.shtml
http://www17.tomshardware.com/mainboard/01q1/010104/amd-133fsb-01.html
http://www.gamepc.com/labs/view_content.asp?id=sdrvsddr&page=1&cookie%5Ftest=1&bhcp=1
http://www.kingston.com/newtech/ddrvssdram.asp

http://www.kingston.com/newtech/rimmvs.asp
http://www.tomshardware.com/mainboard/02q2/020501/ddr400vsrambus-05.html
http://www.thetechguide.com/sdramvsrambus.html
http://www.xbitlabs.com/mainboards/i845g-i845e/
http://www.sonicparts.com/en-us/dept_55.html

Try that and let me know if you need more information.

SDRAM transmits data "one way" down the memory stick whereas DDRAM transmits data both up and down so in effect its a lot quicker.

Again posting answers rather than comments is not the way to go here.  My links as well as jlauster's have information pointing to the same information.  Your answer propsed is just a copy.
Please refer to tips on Comments and answers again please.

Silverz welcome to EE.

We usually write a comment instead of an answer, so the question won't be locked and other experts have the chance to give their opinions, too. Only if you are 150% sure that you have the right answer, we would post it as an answer. Please take a look http://www.experts-exchange.com/jsp/cmtyQuestAnswer.jsp for more information on how to answer questions.

For now I rejected your proposed answer.

** Mindphaser - Community Support Moderator **

DDR RAM is faster and you should buy it

Don't waste your money on SDRAM

Make sure your system is compatible with it!

SDRAM is found in most machines and runs at a speed of 100mhz or 133mhz and performs one operation every clock cycle. DDR (double data rate) RAM stil runs at the same mhz speed, but performs two operations per clock cycle, making DDR RAM twice as fast (in theory, 200mhz and 266mhz respectively). Both use the same type of DRAM chips. you cannot put DDR memory into a sdram board and vice-versa.

I want to know the diffrence bitween SDRAM and DDRAM in simple words. thanks


SDram is listed as PC66/PC100/PC133/PC150/PC166 since it writes "one" chunk of data at a time at these rates (66mhz, 100mhz,etc)

DDR PC1600/PC2100/PC2400/PC2700/PC3000/PC3200/PC3500 is listed as that because those are their respective througputs..

When a DDR module writes, it writes 2 chunks per "clock tick"

So, if a PC100 module writes, it writes at 100Mhz, or a frequency of 100 Million times a second (32 bits of data, or 64 bits of data, depending on the module.. most SDRAM is 64 bit of course) so, barring overhead, etc.. and a lot of other variables, you are talking 800Megabytes a second througput out of pc100 (8 bits x 100million writes = 800 Megabyte) now, before I get flamed, off the top of my head, I can't tell you what the official capability is supposed to be, I just know that the record was 492Mb/second.
I know that PC100 CANNOT do 800Megs a second, but I am trying to show how the OTHER numbers came to be

since DDR PC1600 200MHZ writes at 100MHZ X 2 X 64 BITS it has a theoretical throughput of 1.6 Gigabytes a second

Does it get this rate? NO, does PC100 get 800MB? No

but the theoretical "advertised" (read, not ever possible) maximums of different memory are as such
 

PC1600 = 200MHZ DDR = 100Mhz x 2 Channels = "Double PC100"
PC2100 = 266MHZ DDR = 133MHZ x 2 Channels = "Double PC133"
PC2400 = 300MHZ DDR = 150MHZ x 2 Channels = "Double pC150"
PC2700 = 333MHz DDR = 166Mhz x 2 Channels = "Double pC166"
PC3000 = 366Mhz DDR = 183Mhz x 2 Channels = "no match"
PC3200 = 400MHZ DDR = 200Mhz x 2 Channels = "no match"
PC3500 = 433MHZ DDR = 216Mhz x 2 Channels = "no match"


Now, since I guess his question is based on the "should I buy a computer with DDR" then the answer is yes.. unless of course it's an APPLE G4, which cost more money than their SDR counterparts, but dont run any faster, and in some cases, run SLOWER.

In simple words: SDRAM usually runs at 133MHz
DDR RAM runs at 266MHz

haupta : in one word. : wrong : ?


"SDRAM Runs at 133Mhz" - No, only PC133 runs at 133mhz, PC66,PC100,PC150,PC166, do not.


"DDR ram runs at 266Mhz" - no, only PC2100 ddr ram runs at that speed, as I have shown, DDR runs at "2 x the writes" I list 7 different types of DDR memory, only 1 of which runs at 266mhz

ddr MEANS "Double Data Rate".
it's not called DPC133DR

DDR-SDRAM
Short for Double Data Rate-Synchronous DRAM, a type of SDRAM that supports data transfers on both edges of each clock cycle (the rising and falling edges), effectively doubling the memory chip's data throughput. DDR-SDRAM also consumes less power, which makes it well-suited to notebook computers. DDR-SDRAM is also called SDRAM II.  

(both edges does not mean, as silverz thought, that it reads and writes at the same time..)

Additionally, DDR PC2100 doesn't actually run at 266mhz.. it runs at 133mhz with 2 "channels" for lack of a better term of writing, giving the same performance you would get from the theoretical "PC266-SDRAM"  (if it ever got built

a 'PC800-DDR' module (hypothetical PC66MHZ x 2 module)would be almost identical in performance to pc133 (the tiebreaker, in a situation like this, would be latency... is the PC133 CAS2 where the DDR800 (again, something that doesn't actually exist) is CAS3?