electronic memories capacity

[>> BILLING]

Why electronic memory (eg. flash) capacity is 1, 4, 8, 16, 32, 64, 128
etc. I have read that it is function of some memory parameters, but i do
not know which. Can anybody help me?

 

[James H. Fox]

Why electronic memory (eg. flash) capacity is 1, 4, 8, 16, 32, 64, 128
etc. I have read that it is function of some memory parameters, but i do
not know which. Can anybody help me?

It is just the technology they use to make it. Usually, they increase the
number of transistors they can put on a chip by a factor of 4 every two
years or so, and then they increase the memory capacity accordingly. It is
not economical to increase it by a smaller factor most of the time.

 

[Mike Walsh]

Adding 1 address line will increase addressable capacity by a factor of 4, i.e. twice as many columns and twice as many rows.

It is just the technology they use to make it. Usually, they increase the
number of transistors they can put on a chip by a factor of 4 every two
years or so, and then they increase the memory capacity accordingly. It is
not economical to increase it by a smaller factor most of the time.

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Mike Walsh
West Palm Beach, Florida, U.S.A.

 

[Graeme]

But only on devices with muxed address (DRAMs), not on flash devices (or do
some of these have multiplexed address inputs?).

Adding 1 address line will increase addressable capacity by a factor of 4,

i.e. twice as many columns and twice as many rows.

 

[JS]

But only on devices with muxed address (DRAMs), not on flash devices
(or do some of these have multiplexed address inputs?).

You are correct. Flash, static-ram, eeprom, rom and others typically do not
use muxed address pins. I've never seen them myself but I won't say
absolutely that they they 'never' use muxed address pins. some niche
part may do this but it is NOT common. Each additional address line/pin
doubles the number of accessible addresses and so doubles the potential
memory capacity. Its a binary thing. All forms of dynamic-ram (DRAM, SDRAM,
DDRAM, etc.) are another story but again, each additional address bit will
double the addressible memory and thus the potential memory capacity.

 

[CBFalconer]

You are correct. Flash, static-ram, eeprom, rom and others
typically do not use muxed address pins. I've never seen them
myself but I won't say absolutely that they they 'never' use
muxed address pins. some niche part may do this but it is NOT
common. Each additional address line/pin doubles the number of
accessible addresses and so doubles the potential memory
capacity. Its a binary thing. All forms of dynamic-ram (DRAM,
SDRAM, DDRAM, etc.) are another story but again, each additional
address bit will double the addressible memory and thus the
potential memory capacity.

There is a good reason for that. Dynamic rams need two cycles, one
to address a row of bits, and the other to address a column. So
they can only use 1/2 of the address at a time. The other devices
want to address a particular address instantly, with no timing
complexities.