Components for Building Computers From Scratch/Dimm help

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Question
I do not know if I e mailed you but I think I can ask my Q/A in the right way this time.

The first 168 pin DIMM
and the
184 pin DDR DIMM
and the
240 pin DDR2 DIMM

Am I right all of these are SDR Memory?

Answer
Yes and no, it depends on exactly what we're meaning - SDR (single data rate) memory is not the same as DDR (dual data rate). The DDR and DDR2 memory are, as their name implies, DDR. However all of these types of memory *are* SDRAM (synchronous dynamic RAM). Only the 168-pin DIMM is single data rate though. For clarification on these terms:
https://en.wikipedia.org/wiki/Synchronous_dynamic_random-access_memory
https://en.wikipedia.org/wiki/Double_data_rate
https://en.wikipedia.org/wiki/Synchronous_dynamic_random-access_memory#SDR_SDRAM_.28Single_Data_Rate_synchronous_DRAM.29
https://en.wikipedia.org/wiki/DDR_SDRAM

In general spoken or written parlance, SDR often refers to "single data rate" as opposed to "synchronous dynamic" so saying "SDRAM" is often understood as single data rate, while saying "DDR" is understood as dual data rate, however if your goal is absolute specificity you could use the more awkward SDR-SDRAM and DDR-SDRAM descriptors (although even in contemporary service manuals this is very rarely done).

"Synchronous dynamic" SDRAM differs from older EDO-DRAM (https://en.wikipedia.org/wiki/Dynamic_random-access_memory#Extended_data_out_DRAM_.28EDO_DRAM.29) and FPRAM (https://en.wikipedia.org/wiki/Dynamic_random-access_memory#Fast_page_mode_DRAM_.28FPM_DRAM.29), which are only generally found in very old (>15 years) machines these days.

Finally, there's also RDRAM, which is itself entirely separate - it isn't used in any modern computers (it once was, around ten years ago, used in computers), but there are still embedded devices that rely upon it (the PlayStation 2 and Nintendo 64 game consoles are probably the most notable). More here: https://en.wikipedia.org/wiki/RDRAM

-bob

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Bobbert

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I have nearly two decades of experience in IT, computer repair, and related fields and will attempt to provide the most solid, brand-agnostic advice when it comes time to purchase a new computer, or upgrade an existing machine. I can answer anything from the seemingly basic to the downright complicated - and will do my best to provide this information in a clear and concise manner.

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