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Disk to disk copying with overclocked memory



 
 
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  #1  
Old March 11th 04, 02:07 AM
JT
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Default Disk to disk copying with overclocked memory

On Thu, 11 Mar 2004 00:40:47 GMT, Mark M
wrote:

I use a partition copier which boots off a floppy disk before any
other OS is launched.

If I copy a partition from one hard drive to another, then is there
any risk of data corruption if the BIOS has been changed to
aggressively speed up the memory settings?

For example the BIOS might set the memory to CAS=2 rather than
CAS=3. Or other memory timing intervals might also be set to be
shorter than is normal.

I am thinking that maybe the IDE cable and drive controllers handle
data fairly independently of the memory on the motherboard. So
maybe data just flows up and down the IDE cable and maybe the
motherboard is not involved except for sync pulses.

There are three scenarios I am thinking about:

(1) Copying a partition from one hard drive on one IDE cable to
another hard drive on a different IDE cable.

(2) Copying a partition from one hard drive to another which is on
the same IDE cable.

(3) Copying one partition to another on the same hard drive.

How much effect would "over-set" memory have on these situations?

Do the answers to any of the above three scenarios change if the
copying of large amounts of data files is done from within WinXP?
Personally, I would guess that it is more likely that motherboard
memory comes into play if Windows is involved.


1. All copies go through memory using at least a block sized buffer of ram.
Buffers at least large enough to hold an entire track will be used,
probably larger for more effeciency. Data is always copied from a drive to
a memory buffer first. Might be directly, using DMA (the M is memory), but
it will be to and from memory. What part of memory is used will vary
depending on the program and whether you are running it under windows, but
a single bit error in the wrong place in memory can be a major problem.

2. If your memory timing is aggressive enough that errors are likely, then
there are a number of things that could go wrong. There could be an error
in the data that gets copied. You could also have the wrong disk address
stored in ram so the data goes to the wrong place. Could be the wrong
instruction so the program crashes. Could be any one of hundreds of
possible single bit failures that might go unnoticed. ECC would help here
(would catch most possible memory errors). If you want reliability in
anything (not just copying disks) then don't push your memory (or other
components) to the edge.

JT
  #2  
Old March 11th 04, 02:49 AM
Colin Painter
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Default

If I can add a bit to JT's reply...

If you are overclocking your memory you risk getting more errors than the
guys who built the memory planned on. If the memory is not ECC memory then
you may get more single bit errors which will cause your machine to stop
when they occur. ECC memory can correct single bit errors but non-ECC memory
can only detect them and when that happens windows will blue screen. Most
home PCs have non-ECC memory because it's cheaper.

Overclocking could also cause the occasional double bit error which non-ECC
memory cannot detect. This would be bad. As JT indicates, this could cause
all sorts of mayhem. If you're lucky, windows could execute a broken
instruction or reference a memory address in outer space and then blue
screen. If you are unlucky it could blunder on using bad data and do
something nasty to your file system (or it could harmlessly stick an umlaut
onto the screen somewhere.) Hard to predict.

cp




"Mark M" wrote in message
...
I use a partition copier which boots off a floppy disk before any
other OS is launched.

If I copy a partition from one hard drive to another, then is there
any risk of data corruption if the BIOS has been changed to
aggressively speed up the memory settings?

For example the BIOS might set the memory to CAS=2 rather than
CAS=3. Or other memory timing intervals might also be set to be
shorter than is normal.

I am thinking that maybe the IDE cable and drive controllers handle
data fairly independently of the memory on the motherboard. So
maybe data just flows up and down the IDE cable and maybe the
motherboard is not involved except for sync pulses.

There are three scenarios I am thinking about:

(1) Copying a partition from one hard drive on one IDE cable to
another hard drive on a different IDE cable.

(2) Copying a partition from one hard drive to another which is on
the same IDE cable.

(3) Copying one partition to another on the same hard drive.

How much effect would "over-set" memory have on these situations?

Do the answers to any of the above three scenarios change if the
copying of large amounts of data files is done from within WinXP?
Personally, I would guess that it is more likely that motherboard
memory comes into play if Windows is involved.



  #3  
Old March 11th 04, 02:55 AM
kony
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On Thu, 11 Mar 2004 00:40:47 GMT, Mark M
wrote:

I use a partition copier which boots off a floppy disk before any
other OS is launched.

If I copy a partition from one hard drive to another, then is there
any risk of data corruption if the BIOS has been changed to
aggressively speed up the memory settings?


Yes, a relatively high risk.


For example the BIOS might set the memory to CAS=2 rather than
CAS=3. Or other memory timing intervals might also be set to be
shorter than is normal.


Yes, that'll _potentially_ cause errors, corrupt the data.

I am thinking that maybe the IDE cable and drive controllers handle
data fairly independently of the memory on the motherboard. So
maybe data just flows up and down the IDE cable and maybe the
motherboard is not involved except for sync pulses.


It's involved. Hint: Consider what "DMA" stands for.


There are three scenarios I am thinking about:

(1) Copying a partition from one hard drive on one IDE cable to
another hard drive on a different IDE cable.

(2) Copying a partition from one hard drive to another which is on
the same IDE cable.

(3) Copying one partition to another on the same hard drive.

How much effect would "over-set" memory have on these situations?


It has the same effect on all, that "IF" the memory is set incorrectly or
defective (or motherboard issue, etc), that if errors occur all of the
above scenarios are a risk.

Do the answers to any of the above three scenarios change if the
copying of large amounts of data files is done from within WinXP?
Personally, I would guess that it is more likely that motherboard
memory comes into play if Windows is involved.


It's the same risk, but with more memory used there's even a greater
chance of errors, not necessarily all occuring in the data transfer but
ALSO the OS, so both the backup AND the OS would potentially be using
corrupt data... never boot to the OS if there's any question of memory
instability, else be prepared and expecting to reinstall everything unless
you can restore or recreate every file written during that interval of
operation.

  #4  
Old March 11th 04, 06:21 AM
CBFalconer
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Default

Colin Painter wrote:

If I can add a bit to JT's reply...

If you are overclocking your memory you risk getting more errors
than the guys who built the memory planned on. If the memory is
not ECC memory then you may get more single bit errors which will
cause your machine to stop when they occur. ECC memory can
correct single bit errors but non-ECC memory can only detect them
and when that happens windows will blue screen. Most home PCs
have non-ECC memory because it's cheaper.


Correction here - non ECC memory won't even detect any errors, it
will just use the wrong value. Sometimes that MAY cause the OS to
crash. Unfortunately the rest of the thread is lost due to
top-posting.

--
Chuck F ) )
Available for consulting/temporary embedded and systems.
http://cbfalconer.home.att.net USE worldnet address!

  #5  
Old March 11th 04, 06:37 AM
CJT
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CBFalconer wrote:
Colin Painter wrote:

If I can add a bit to JT's reply...

If you are overclocking your memory you risk getting more errors
than the guys who built the memory planned on. If the memory is
not ECC memory then you may get more single bit errors which will
cause your machine to stop when they occur. ECC memory can
correct single bit errors but non-ECC memory can only detect them
and when that happens windows will blue screen. Most home PCs
have non-ECC memory because it's cheaper.



Correction here - non ECC memory won't even detect any errors, it
will just use the wrong value. Sometimes that MAY cause the OS to
crash. Unfortunately the rest of the thread is lost due to
top-posting.

You seem to have confused ECC and parity. ECC means error checking
and correcting, which involves more redundancy than simple single bit
parity error checking.

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .
  #6  
Old March 11th 04, 06:49 AM
Rod Speed
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Default


"CJT" wrote in message ...
CBFalconer wrote:
Colin Painter wrote:

If I can add a bit to JT's reply...

If you are overclocking your memory you risk getting more errors
than the guys who built the memory planned on. If the memory is
not ECC memory then you may get more single bit errors which will
cause your machine to stop when they occur. ECC memory can
correct single bit errors but non-ECC memory can only detect them
and when that happens windows will blue screen. Most home PCs
have non-ECC memory because it's cheaper.



Correction here - non ECC memory won't even detect any errors, it
will just use the wrong value. Sometimes that MAY cause the OS to
crash. Unfortunately the rest of the thread is lost due to
top-posting.


You seem to have confused ECC and parity.


Or you have. **** all ram is parity anymore.

ECC means error checking and correcting, which involves
more redundancy than simple single bit parity error checking.


Which isnt seen much anymore.


  #7  
Old March 11th 04, 07:41 AM
CBFalconer
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Posts: n/a
Default

CJT wrote:
CBFalconer wrote:
Colin Painter wrote:

If I can add a bit to JT's reply...

If you are overclocking your memory you risk getting more errors
than the guys who built the memory planned on. If the memory is
not ECC memory then you may get more single bit errors which will
cause your machine to stop when they occur. ECC memory can
correct single bit errors but non-ECC memory can only detect them
and when that happens windows will blue screen. Most home PCs
have non-ECC memory because it's cheaper.


Correction here - non ECC memory won't even detect any errors, it
will just use the wrong value. Sometimes that MAY cause the OS to
crash. Unfortunately the rest of the thread is lost due to
top-posting.

You seem to have confused ECC and parity. ECC means error checking
and correcting, which involves more redundancy than simple single bit
parity error checking.


Nothing uses parity checking today - that requires writing
individual 9 bit bytes. Expanded to a 64 bit wide word (for the
various Pentia etc.) the parity or ECC bits both fit in an extra 8
bits, i.e. a 72 bit wide word. If todays systems have no ECC they
have no checking of any form. ECC is actually no harder to handle
on wide words.

Memory configurations that can use parity can use ECC, the reverse
is not true.

Exception - some embedded systems with smaller memory paths may
use parity.

--
Chuck F ) )
Available for consulting/temporary embedded and systems.
http://cbfalconer.home.att.net USE worldnet address!

  #8  
Old March 11th 04, 01:44 PM
JT
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Default

On Thu, 11 Mar 2004 10:20:18 GMT, Mark M
wrote:

CBFalconer wrote:

Nothing uses parity checking today - that requires writing
individual 9 bit bytes. Expanded to a 64 bit wide word (for
the various Pentia etc.) the parity or ECC bits both fit in an
extra 8 bits, i.e. a 72 bit wide word. If todays systems have
no ECC they have no checking of any form. ECC is actually no
harder to handle on wide words.

Memory configurations that can use parity can use ECC, the
reverse is not true.

Exception - some embedded systems with smaller memory paths
may use parity.



Does the motherboard have to support ECC?

Or can you always put a stick of ECC memeory where there had been
non-ECC memory before?


For ECC to work, the motherboard has to support it. If you put ECC in a
motherboard that doesn't support ECC, it will usually operate just fine,
but with no Error correction.

JT
  #9  
Old March 11th 04, 01:55 PM
J. Clarke
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Posts: n/a
Default

Mark M wrote:

CBFalconer wrote:

Nothing uses parity checking today - that requires writing
individual 9 bit bytes. Expanded to a 64 bit wide word (for
the various Pentia etc.) the parity or ECC bits both fit in an
extra 8 bits, i.e. a 72 bit wide word. If todays systems have
no ECC they have no checking of any form. ECC is actually no
harder to handle on wide words.

Memory configurations that can use parity can use ECC, the
reverse is not true.

Exception - some embedded systems with smaller memory paths
may use parity.



Does the motherboard have to support ECC?

Or can you always put a stick of ECC memeory where there had been
non-ECC memory before?


The motherboard has to support it, otherwise at best the additional bits
that support ECC will be ignored.

I find it highly annoying that Intel etc have decided that "consumers" don't
need this and so not implemented it in most of the available chipsets.

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)
  #10  
Old March 11th 04, 02:12 PM
CBFalconer
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Posts: n/a
Default

Mark M wrote:
CBFalconer wrote:

Nothing uses parity checking today - that requires writing
individual 9 bit bytes. Expanded to a 64 bit wide word (for
the various Pentia etc.) the parity or ECC bits both fit in an
extra 8 bits, i.e. a 72 bit wide word. If todays systems have
no ECC they have no checking of any form. ECC is actually no
harder to handle on wide words.

Memory configurations that can use parity can use ECC, the
reverse is not true.

Exception - some embedded systems with smaller memory paths
may use parity.


Does the motherboard have to support ECC?


Yes


Or can you always put a stick of ECC memeory where there had been
non-ECC memory before?


No. Even if the MB supports ECC you have to have ALL the memory
ECC capable before it will function. Otherwise the system can't
tell a massive failure from a non-ECC area.

--
Chuck F ) )
Available for consulting/temporary embedded and systems.
http://cbfalconer.home.att.net USE worldnet address!


 




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