a Tech Question

Hi,

I was reading up on the difference between BIOS & CMOS, and think I
now how a grip on it, but I am wondering why the cmos/config program
uses ram instead of rom?
Wouldnt this do away with the necessity of the cmos battery?

thanks for any enlightenment.

Sorry, let me rephrase, I know the battery would be needed.
What I meant was, why is ram the choice of memory for the cmos
instead of rom?
Hope this makes sense.


"shep" wrote in message
...
Hi,

I was reading up on the difference between BIOS & CMOS, and think I
now how a grip on it, but I am wondering why the cmos/config program
uses ram instead of rom?
Wouldnt this do away with the necessity of the cmos battery?

thanks for any enlightenment.

"shep" wrote in message
...
Sorry, let me rephrase, I know the battery would be needed.
What I meant was, why is ram the choice of memory for the cmos
instead of rom?
Hope this makes sense.


"shep" wrote in message
...
Hi,

I was reading up on the difference between BIOS & CMOS, and think I
now how a grip on it, but I am wondering why the cmos/config program
uses ram instead of rom?
Wouldnt this do away with the necessity of the cmos battery?

thanks for any enlightenment.



Hi,
I'm no expert on this subject but if the memory was ROM (Read Only Memory)
you wouldn't be able to make changes to the BIOS settings. You'd need a ROM
burner to do that - hardly practical. That's my take on it anyway.

HTH

Hi,
I'm no expert on this subject but if the memory was ROM (Read Only Memory)
you wouldn't be able to make changes to the BIOS settings. You'd need a
ROM burner to do that - hardly practical. That's my take on it anyway.

HTH

My thoughts exactly.
You need to be able to adjust settings in BIOS to take account of the
particular hardware connected, like what size/type of hard disks connected,
what cards in which PCI slots, the date and time, amount of RAM installed
etc.
If it was ROM, then what was made in the factory would be all you could ever
have, and no clock!

Good Luck
BarryG

CMOS is used to store your computer's configuration data because it can
change. If you add more memory, a new drive, a new video card, etc. CMOS
would need to be updated. Since it must change it must be stored in RAM
memory.

--
Richard G. Harper [MVP Shell/User]
* NEW! Catch my blog ... http://msmvps.com/blogs/rgharper/
* PLEASE post all messages and replies in the newsgroups
* The Website - http://rgharper.mvps.org/
* HELP us help YOU ... http://www.dts-l.org/goodpost.htm


"shep" wrote in message
...
Hi,

I was reading up on the difference between BIOS & CMOS, and think I
now how a grip on it, but I am wondering why the cmos/config program
uses ram instead of rom?
Wouldnt this do away with the necessity of the cmos battery?

thanks for any enlightenment.

The BIOS chips (since 1990) use PROM or EPROM and not 'just plain old ROM'
and are consequently able to be re-programmed (or at least partially
re-programmed) by the user when adjusting (permitted) BIOS setting

For a slightly more in-depth (but not too technical) explanation see the
section "BIOS as firmware" at :-

http://en.wikipedia.org/wiki/BIOS

HTH

Mart



"BarryG" wrote in message
...

Hi,
I'm no expert on this subject but if the memory was ROM (Read Only
Memory) you wouldn't be able to make changes to the BIOS settings. You'd
need a ROM burner to do that - hardly practical. That's my take on it
anyway.

HTH

My thoughts exactly.
You need to be able to adjust settings in BIOS to take account of the
particular hardware connected, like what size/type of hard disks
connected, what cards in which PCI slots, the date and time, amount of
RAM installed etc.
If it was ROM, then what was made in the factory would be all you could
ever have, and no clock!

Good Luck
BarryG

Thanks to all repliers.

I still have a couple of things that are bugging me, will post back
when I can word my concern correctly.


"shep" wrote in message
...
Hi,

I was reading up on the difference between BIOS & CMOS, and think I
now how a grip on it, but I am wondering why the cmos/config program
uses ram instead of rom?
Wouldnt this do away with the necessity of the cmos battery?

thanks for any enlightenment.

"shep" wrote in news:#58NBrkMHHA.4384
@TK2MSFTNGP03.phx.gbl:

Thanks to all repliers.

I still have a couple of things that are bugging me, will post back
when I can word my concern correctly.


"shep" wrote in message
...
Hi,

I was reading up on the difference between BIOS & CMOS, and think I
now how a grip on it, but I am wondering why the cmos/config program
uses ram instead of rom?
Wouldnt this do away with the necessity of the cmos battery?

thanks for any enlightenment.





This scheme was developed at a time when nonvoltaile memory was either:
EEPROM - handy but expensive at the time
UV eraseable EPROM - expensive, and requires UV light to erase.
PROM of various types - handy for the BIOS, but not reprogrammable
RAM with battery backup - relatively inexpensive
others - expensive or required too much room or carried too much overhead

A battery was required anyway to keep the calendar/clock running, so RAM
with battery backup made good economic sense.

Nowadays, the RAM, calendar/clock and other items are integrated together
in one chip. Putting flash memory into the chip would drive up the cost.
Putting external serial flash memory external to the chip would be handy
but would also drive up the cost a little.

[Personally, I would prefer to have these parameters in flash so that they
are not lost in the case of a battery failure, but cost seems to have
pushed the vendors in the other direction.]


--
Ian Shef 805/F6 * These are my personal opinions
Raytheon Company * and not those of my employer.
PO Box 11337 *
Tucson, AZ 85734-1337 *

Interesting (personal) insight Ian - thanks for your follow-up which makes
sound technical (but not seemingly, commercial g) sense.

Mart


"Ian Shef" wrote in message
0...
"shep" wrote in news:#58NBrkMHHA.4384
@TK2MSFTNGP03.phx.gbl:

Thanks to all repliers.

I still have a couple of things that are bugging me, will post back
when I can word my concern correctly.


"shep" wrote in message
...
Hi,

I was reading up on the difference between BIOS & CMOS, and think I
now how a grip on it, but I am wondering why the cmos/config program
uses ram instead of rom?
Wouldnt this do away with the necessity of the cmos battery?

thanks for any enlightenment.





This scheme was developed at a time when nonvoltaile memory was either:
EEPROM - handy but expensive at the time
UV eraseable EPROM - expensive, and requires UV light to erase.
PROM of various types - handy for the BIOS, but not reprogrammable
RAM with battery backup - relatively inexpensive
others - expensive or required too much room or carried too much overhead

A battery was required anyway to keep the calendar/clock running, so RAM
with battery backup made good economic sense.

Nowadays, the RAM, calendar/clock and other items are integrated together
in one chip. Putting flash memory into the chip would drive up the cost.
Putting external serial flash memory external to the chip would be handy
but would also drive up the cost a little.

[Personally, I would prefer to have these parameters in flash so that they
are not lost in the case of a battery failure, but cost seems to have
pushed the vendors in the other direction.]


--
Ian Shef 805/F6 * These are my personal opinions
Raytheon Company * and not those of my employer.
PO Box 11337 *
Tucson, AZ 85734-1337 *

and again.... thanks to all, has been interesting, will copy and
keep posts for reference.
(if you dont ask, you dont get)


"Mart" wrote in message
...
Interesting (personal) insight Ian - thanks for your follow-up which makes
sound technical (but not seemingly, commercial g) sense.

Mart


"Ian Shef" wrote in message
0...
"shep" wrote in news:#58NBrkMHHA.4384
@TK2MSFTNGP03.phx.gbl:

Thanks to all repliers.

I still have a couple of things that are bugging me, will post back
when I can word my concern correctly.


"shep" wrote in message
...
Hi,

I was reading up on the difference between BIOS & CMOS, and think I
now how a grip on it, but I am wondering why the cmos/config program
uses ram instead of rom?
Wouldnt this do away with the necessity of the cmos battery?

thanks for any enlightenment.





This scheme was developed at a time when nonvoltaile memory was either:
EEPROM - handy but expensive at the time
UV eraseable EPROM - expensive, and requires UV light to erase.
PROM of various types - handy for the BIOS, but not reprogrammable
RAM with battery backup - relatively inexpensive
others - expensive or required too much room or carried too much
overhead

A battery was required anyway to keep the calendar/clock running, so RAM
with battery backup made good economic sense.

Nowadays, the RAM, calendar/clock and other items are integrated
together
in one chip. Putting flash memory into the chip would drive up the
cost.
Putting external serial flash memory external to the chip would be handy
but would also drive up the cost a little.

[Personally, I would prefer to have these parameters in flash so that
they
are not lost in the case of a battery failure, but cost seems to have
pushed the vendors in the other direction.]


--
Ian Shef 805/F6 * These are my personal opinions
Raytheon Company * and not those of my employer.
PO Box 11337 *
Tucson, AZ 85734-1337 *