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Episode 5: RAM – Show Notes

What is RAM? – Random Access Memory

What makes RAM work?

What are some key features to RAM? Two of the biggest features to take into consideration when shopping for RAM are capacity and speed.

What does the 9-9-9-24 mean? This refers to the timing of the RAM. If you buy RAM at 2 different times, you need to make sure any RAM you may add at a later date has the same timing numbers.
  1. CAS (tCL) Timing – 1st number of the set of 4 – Column Address Strobe/Select – Sets the latency(delay) between when the when the Read command is sent and when it is acted on
  2. tRCD Timing – 2nd number in the set of 4 – RAS to CAS delay (Row Address Strobe/Select) – Sets the amount of time in cycles for issuing an active command and the read/write commands
  3. tRP Timing – 3rd number in the set of 4 – Row Precharge Time – The minimum time between the active commands and the read/writes of the next bank on the memory module
  4. tRAS Timing – 4th and largest number in the set of 4 – Min RAS Active Time – The amount of time a row being activated by precharge and deactivated. A row cannot be deactivated until tRAS has completed. The lower this is, the faster the performance, but if it is set too low, it can cause data corruption by deactivating the row too soon.
    1. tRAS = tCL + tRCD + tRP(+/-1) This equation gives enough time to close the bank and prevent data corruption. Note: The equation is an approximation of how they determine the final number and not the exact method.
Clock Frequency
The PC numbers, like PC1600
How come a 32bit OS can only use about 4 GB RAM(technically think it is closer to 3.5GB), while a 64bit can handle a max of 192 GB?
SIMM – Single In-line Memory Module
DIMM – Dual In-line Memory Module
DRAM – Dynamic Random Access Memory
SRAM – Static Random Access Memory
SDRAM – Synchronous DRAM
SDR – Single Data Rate
DDR  – Double Data Rate
DDR2
  1. Single Channel
  2. Dual Channel
DDR3
  1. Dual Channel
  2. 3 Channel

Cooling – All electronics dissipate some heat when being used, since there are no components that are 100% efficient, this will always be true.

Troubleshooting RAM issues

Whose RAM should I buy?

NEWS!!!!!!!!!!!!!! –  memristors  the future of flash memory and maybe RAM
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Posted in Hardware, RAM, Show Notes.


2 Responses

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  1. spyder says

    so Ram labeled like this. 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800)

    is the 1600 your pc number or is pc3 12800 you ram bandwidth?

  2. Grebog says

    From the numbers you posted, I would say the 1600 would be the RAM’s data rate in MT/s and the bandwidth is 12,800 MB/s.

    The data rate is closely associated to the clock frequency, since DDR3 is dual data rate, understandably twice the clock frequency.



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