Registers and RAM: Crash Course Computer Science #6

uniform bank of addressable memory

256 addresses, and at each address, we can read or write an 8-bit value

For 256 bits of memory, we only need

35 wires - 1 data wire, 1 write enable wire, 1 read enable wire, and 16 rows and columns for the selection

If we opened up a stick of 1 megabyte RAM you would see is

8 memory modules soldered onto the board. If we carefully opened up one of these modules and zoomed in, you would see are 32 squares of memory. Zoom into one of those squares, and we can see each one is comprised of 4 smaller blocks. If we zoom in again, we get down to the matrix of individual bits. This is a matrix of 128 by 64 bits. That's 8192 bits in total. Each of our 32 squares has 4 matrices, so that's 32 thousand, 7 hundred and 68 bits. And there are 32 squares in total. So all in all, that's roughly 1 million bits of memory in each chip. Our RAM stick has 8 of these chips, so in total, this RAM can store 8 million bits, otherwise known as 1 megabyte.

Multiplexer

A circuit that directs one of several digital signals to a single output, depending on the states of several select inputs.

16x16 latch matrix

For 256 bits, we need a 16 by 16 grid of latches with 16 rows and columns of wires. To activate any one latch, we must turn on the corresponding row AND column wire.

AND OR Latch

It has two inputs, a "set" input, which sets the output to a 1, and a "reset" input, which resets the output to a 0. If set and reset are both 0, the circuit just outputs whatever was last put in it. In other words, it remembers a single bit of information! Memory!

NVRAM

Non-Volatile Random Access Memory

RAM

Random Access Memory - temporary place to store material that works quickly. erased when computer turns off. Volatile.

Flash Memory

Type of nonvolatile memory that can be erased electronically and rewritten.

If we put 8 latches side-by-side, we can store 8 bits of information like an 8-bit number. A group of latches operating like this is called

a register, which holds a single number, and the number of bits in a register is called its width.

Gated Latch

can be opened or closed

DRAM

dynamic random access memory

The action of getting the data out is called ________________.

reading

SRAM

static random access memory

abstraction

the quality of dealing with ideas rather than events

To address a gigabyte - or a billion bytes of memory -

we need 32-bit addresses.

The action of putting data into memory is called ___________.

writing