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8
Hardware/Memory/RAM_types.md
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@ -26,6 +26,14 @@ SRAM (Static Random Access Memory) is also volatile memory but, in terms of the
### Relative speeds ### Relative speeds
The table below details the relative speeds of the different types of memory and those of other types of motherboard storage. The table below details the relative speeds of the different types of memory and those of other types of motherboard storage.
| Storage type | Access speed (clock cycles) | Relative times slower |
|--------------|-----------------------------|-----------------------|
| CPU register | 2 | |
| L1 cache | 4 | 2x |
| L2 cache | 6-20 | 3-10x |
| DRAM memory | 50 | 25x |
| Harddisk | 2000 | 1000x |
## References ## References

2
Hardware/Memory/Role_in_computation.md
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@ -15,6 +15,8 @@ The following steps outline the way in which memory interacts with the processor
> This is a simplified account; it is not the case that only single requests are passed back and forth. This would be inefficient and time-wasting. The kernel sends to the CPU not just the first instruction in the requested file but also a number of instructions that immediately follow it. > This is a simplified account; it is not the case that only single requests are passed back and forth. This would be inefficient and time-wasting. The kernel sends to the CPU not just the first instruction in the requested file but also a number of instructions that immediately follow it.
![](/img/memory-flow.svg)
Every part of the above process - the journey accross the bus, the lookup in the controller, the operations on the DRAM, the journey back accross the bus - takes muliple CPU clock cycles. Every part of the above process - the journey accross the bus, the lookup in the controller, the operations on the DRAM, the journey back accross the bus - takes muliple CPU clock cycles.
## The role of the cache ## The role of the cache