ELi5:why do memories(SRAM/DRAM) need continuous refreshing to store a bit of information?
In: Engineering
SRAM does not need any refreshing. It is called static ram for a reason. It doo not need constant power to keep the information. You store the data in transistors connected in a circle, most common is two inverters in a circle.
DRAM needs refreshing because it stores data as electric charge in a capacitor and they do leak some and will get discharged over time.
Today when it is SDRAM that is common they have automatic refresh so you just need to signal auto-refresh often enough and it takes care of the refreshing itself. Older DRAM you needed external logic for part of the refreshing procedure.
I believe only DRAM (the more common type) needs to be refreshed. DRAM uses a capacitor to store information because it’s smaller and cheaper. However, a capacitor is inherently temporary and will drain over time. Because the capacitor drains, the bit will eventually be lost. So the capacitor needs to be recharged every so often to prevent it from draining.
Edit: fixed mistake.
The issue is that the charge placed into the tiny capacitors that store the bits will slowly leak off (I say “slowly”, it is refeshed about every 64 milliseconds). The insulation of the capacitors isn’t perfect and charge cannot be stored forever on its own. There is a tradeoff between long storage times without access to power, and rapid access with frequent changes not wearing it out.
The bits in RAM are effectively mini capacitors. If they are not refreshed they will drain all drain to 0.
To provide a bit more details on capacitors:
Ever take a rubber balloon, rub it against your hair and stick it to the wall? That’s the same principle that a capacitor works on. Sure, the balloon will stick to the wall for a while. But not forever. For balloons in a good dry environment, maybe they’ll stick to the wall for a few hours. For the microscopic capacitors used to store the data for DRAM, it’s on the orders of tens of milliseconds.
Okay, this answer is not going to make much sense because it was generated from an AI program (GPT-2), but here it goes:
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The answer is simple: we need to go back in time to get the information.
This is called temporal retrieval hypothesis. Time is not static when it is observed but flows differently when it is in the memory. For example, the time of viewing a movie is different when it is seen from 15 minutes to five hours later, even though the time of viewing is the same. But the same movie still has a different flow of time when it is viewed from the past, for example, from nine minutes to 30 seconds.
This phenomenon is called temporal reversal. A memory can change duration within a single memory reference point. The result is that a memory can be recorded in a different reference point simultaneously.
Time is also a fluid medium. Time is affected by external stimuli and is subject to external laws. For example, the laws of physics prohibit you from driving a car into a tree while the car is moving at 120 miles per hour.
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Didn’t really make much sense, but there is your answer from an AI being.
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