Does CPU cache have a life span?

[incantation_goat]

I ask this because I know that RAM has a limited life span as well as SSDs. Does the on-die cache memory on a CPU wear out? Has anyone experienced this or have any knowledge on this? I am not asking for any particular reason, just curious. Thanks in advanced!

 

[hunter315]

Whats the lifespan on RAM? Its pretty long from experience. SSDs use flash memory which has a fixed number of writes as writes run it at higher voltage and do slight damage each time.

RAM and the cache on the CPU which is SRAM are volitile memory, they dont store things permantly and run at low voltage, they store data in flip flops which are built from transistors(similar to the ones in the core of the CPU) and have a pretty long life span, at least 5 years of continuous usage, probably closer to 10.

Consider how many old electronic devices there are still out and about, transistors are quite durable and dont wear out from usage, usually only from high voltage or current that is outside their design specs.

 

[incantation_goat]

Thank you kindly. So SSDs are not made up of transistors? I know this is all pretty basic, but just trying to wrap my mind around SSD vs. RAM technology.

 

[fazers_on_stun]

Whats the lifespan on RAM? Its pretty long from experience. SSDs use flash memory which has a fixed number of writes as writes run it at higher voltage and do slight damage each time.

RAM and the cache on the CPU which is SRAM are volitile memory, they dont store things permantly and run at low voltage, they store data in flip flops which are built from transistors(similar to the ones in the core of the CPU) and have a pretty long life span, at least 5 years of continuous usage, probably closer to 10.

Consider how many old electronic devices there are still out and about, transistors are quite durable and dont wear out from usage, usually only from high voltage or current that is outside their design specs.

True - however DRAM (incl. SDRAM, DDR, DDR2, DDR3, ... DDR5 etc) is more like a switch and capacitor to temporarily store the data, which is why they need to be refreshed every microsecond or so, as the data leaks off the capacitor. SRAM is the one with the flip-flops that don't need refreshing - they'll hold their data as long as the power remains on.

 

[Leaps-from-Shadows]

SSDs use memory cells that only have a certain lifetime, measured in write cycles -- each cell can only be written to a certain number of times before it ceases to function. To combat this, SSDs have special "wear-leveling" routines that make sure new cells are written to first, before already-used cells are written to. And all SSDs have extra memory set aside for when cells do eventually die, and they use these new cells as replacements. However, they only have a certain amount of spare cells.

And yes, RAM and CPUs can fail, but they are designed from the beginning for a 10-year life cycle. That's much longer than they will be actually used.

 

[fazers_on_stun]

Thank you kindly. So SSDs are not made up of transistors? I know this is all pretty basic, but just trying to wrap my mind around SSD vs. RAM technology.

SSDs work by having an extra, "floating" gate between the read/write gate and the transistor channel. Its called a "floating" gate because it is completely insulated from anything else, so whatever charge is on the gate sits there until a rewrite or erase occurs.

To write or rewrite data onto a floating-gate transistor, an overvoltage is applied between the read/write gate and the channel, which causes charge to be injected through the insulation onto the floating gate (or removed from same in the case of writing a zero). Since the floating gate sits much closer to the transistor channel than the read/write gate, whatever charge resides on the floating gate controls whether the transistor is on or off.

As you can imagine, this charge injection is not very good for the insulation (which used to be SiO2 aka glass - dunno what they use currently). After so many write cycles, some charge gets stuck in the insulation and then it builds up enough to affect the operation of the transistor, which then becomes unwriteable and thus useless since it is permanently stuck holding either a one or zero. Hence the limited write lifetime of SSDs.

 

[incantation_goat]

Great answers. I get the difference now and why non volatile memory has a shorter life.