2 . Memory Management Flashcards
What is in memory ?
data
Is it good for cpu and memory to be synchronous?
Yes because asynchronous communication will make us lose cycles between cpu and memory
What are the types of memory ?
- SRAM
- DRAM
Which is faster , sram or dram ?
SRAM is faster but expensive it needs consistent power
Why SRAM is expensive than DRAM ?
SRAM needs 6 transistors with power to store 1 bit
DRAM needs 1 transistors per 1 bit
Why it is called dynamic ram ?
Because it needs to get refreshed once the capacitors started losing energy , sense amplifer will read them and write them back to the capacitor
What is write through cache in memory ?
When cpu going to write , it will write to sense amplifer and sense amplifer will write to the capacitor
How the cpu reads from memory ? Does it read directly from the capacitors ?
Cpu ping the sense amplifer and the sense amplifer will read the capacitor , you CAN NOT read directly from capacitor
Which is faster SDRAM or DRAM ?
SDRAM , because the DRAM is are slow of the missed cycle speed between cpu and memory
What is DDR SDRAM ?
double data rate SRAM which allows receiveing and sending in each cycle between cpu and memory
Can a cpu fetch 1 byte from memory in DDR4 ?
No it must read 64 bytes which are the 64 pins
What is the difference between DDR4 and DDR5 ?
DDR4 : has one bus with 64 pin
DDR5: has two buses splited into two channels each channel has 32 pin io bus
When cpu read memory and it reads 64 bytes , where are they cached to ?
They are cached into the L1 cpu cache
What is the difference between capacitors and transistors ?
Capacitors contain a charge 0/1 , transistor is a gate to access the capacitors
What are the rows and columns in memory ?
Rows : bunch of memory cells (capacitors )
Columns : contains a bunch of memory cells connected to a sense amplifier
