37 lines
1.4 KiB
Markdown
37 lines
1.4 KiB
Markdown
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---
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tags: [memory, hardware]
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created: Friday, July 12, 2024
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---
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# DRAM and SRAM memory
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There are two types of RAM memory: [SRAM and DRAM](./DRAM_and_SRAM_memory.md).
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### DRAM
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DRAM uses capacitors to create the memory cell:
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> a **capacitor** is an electronic component that stores electrical energy in an
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> electrical field. A device which can accumulate and release electrical charge.
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In a DRAM cell, each bit of data is stored as a charge in a capacitor. The
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presence of charge represents a '1' bit and the absence of charge represents a
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'0' bit. Each of these cells is paired with a [transistor](Transistors.md) that
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controls the reading and writing of data.
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However capacitors lose [charge](Current.md) over time due to leaks. As a result
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DRAM is memory that needs to be refreshed (recharged) frequently. For this
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reason and because it only uses one transistor and capacitor per bit, DRAM is
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the less expensive form of volatile memory.
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### SRAM
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SRAM (Static Random Access Memory) is also volatile memory but its electronical
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implementation is different. Unlike DRAM it doesn't use capacitors. Consequently
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the transistors do not leak or need to be refreshed, hence why SRAM is _static_
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and DRAM is _dynamic_.
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SRAM uses [flip flops](Flip_flops.md) to store the bits. It also uses multiple
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transistors per bit. This makes it faster than DRAM but more expensive. DRAM is
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at least ten times slower than SRAM.
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