On 3/1/06, Toby 'qubit' Cubitt
<[EMAIL PROTECTED]> wrote:
On Wed, Mar 01, 2006 at 04:16:33PM -0500, Ryan Holt wrote:
> Is there any difference between ROM and NVRam?
Yes. ROM is a WORM medium (write once, ready many times). The data
stored in a PROM (programmable read only memory) is literally burned
in by applying high-voltage pulses to the chip.
There's also EPROM (eraseable PROM) which can be erased by exposing
the chip to ultraviolet light, and EEPROM (electrically eraseable
PROM). If we're being pedantic, ROM is a misnomer for these, since
they're not really "write once".
NVRAM (non-volatile random access memory) is similar to EEPROM in some
ways: it can be written and erased many times, and maintains its data
even when power is disconnected. MRAM, FRAM, etc. are forms of
NVRAM. Flash memory is I believe a more modern form of EEPROM. They
all differ in the physical technology used on the chip, and have
different properties, such as how many times the memory can be erased
and rewritten, how fast writing and reading is, etc.
Also, Wikipedia says:
"...there is a convention to reserve the term EEPROM [for] byte-wise
writable memories compared to block-wise writable flash memories."
> I think I mis-spoke when I said ROM; because it's actually Non Volatile Ram.
You *could* have meant PROM, but NVRAM sounds much more likely ;-)
Toby
--
PhD Student
Quantum Information Theory group
Max Planck Institute for Quantum Optics
Garching, Germany
email: [EMAIL PROTECTED]
web: www.dr-qubit.org
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