Hi,
I know it is not a good thing to do overclocking, but i am wondering
how bad it is to go around 2% above the recommended max frequency (
266 to 271 MHz in my case ), this is for a SHARC 21375. I am sure it
is not a good practice, but i expect the safety margin to be more than
+2% ?
What do you think ?
Laurent
How much overclocking ?
Started by ●October 16, 2006
Reply by ●October 17, 20062006-10-17
On Tuesday 17 October 2006 00:25, Laurent wrote:
> I know it is not a good thing to do overclocking, but i am wondering
> how bad it is to go around 2% above the recommended max frequency (
> 266 to 271 MHz in my case ), this is for a SHARC 21375. I am sure it
> is not a good practice, but i expect the safety margin to be more than
> +2% ?
>
> What do you think ?
>
> Laurent
This does not depend on the processor chip alone.
The overall quality of the PCB, chip capacitors, clocking circuitry, power
supply and the HF capability of your layout will have tremendous influence.
Though I'm not familiar with the 21375, I'm sure that the safety margin is big
enough for your purpose, if all other parameters are ideal.
If there's a safety margin, it is dedicated to these issues:
- production tolerances
- environmental issues (temperature, humidity, ...)
- and the above hardware issues ...
If you want to overclock the processor, just make sure that temperature stays
within a small band, optimize your layout, etc.
After all that, increase the clock frequency by more than 2%, let's say by
4%, test a couple of processor chips, sort those out, which fail at 4%, and
then use the rest at 2%.
If you cannot do this, increase your production, test all parts at increased
temperature, and sort out those which fail at first.
Be aware, that success isn't guaranteed over production, since you might
receive pieces which behave properly, but then another production charge may
provide pieces which cause lots of trouble when overclocked.
Failure caused by overclocking can be very tricky to find/trace - often they
happen spuriously and are not reproducible.
Besides: Analog Devices might give you a more sophisticated response if you
contact their technical support and describe your intention.
Usually they are very cooperative, if they understand your need.
Bernhard
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> I know it is not a good thing to do overclocking, but i am wondering
> how bad it is to go around 2% above the recommended max frequency (
> 266 to 271 MHz in my case ), this is for a SHARC 21375. I am sure it
> is not a good practice, but i expect the safety margin to be more than
> +2% ?
>
> What do you think ?
>
> Laurent
This does not depend on the processor chip alone.
The overall quality of the PCB, chip capacitors, clocking circuitry, power
supply and the HF capability of your layout will have tremendous influence.
Though I'm not familiar with the 21375, I'm sure that the safety margin is big
enough for your purpose, if all other parameters are ideal.
If there's a safety margin, it is dedicated to these issues:
- production tolerances
- environmental issues (temperature, humidity, ...)
- and the above hardware issues ...
If you want to overclock the processor, just make sure that temperature stays
within a small band, optimize your layout, etc.
After all that, increase the clock frequency by more than 2%, let's say by
4%, test a couple of processor chips, sort those out, which fail at 4%, and
then use the rest at 2%.
If you cannot do this, increase your production, test all parts at increased
temperature, and sort out those which fail at first.
Be aware, that success isn't guaranteed over production, since you might
receive pieces which behave properly, but then another production charge may
provide pieces which cause lots of trouble when overclocked.
Failure caused by overclocking can be very tricky to find/trace - often they
happen spuriously and are not reproducible.
Besides: Analog Devices might give you a more sophisticated response if you
contact their technical support and describe your intention.
Usually they are very cooperative, if they understand your need.
Bernhard
----
Diese E-Mail enthaelt vertrauliche und/oder rechtlich geschuetzte
Informationen. Wenn Sie nicht der richtige Adressat sind oder diese
E-Mail irrtuemlich erhalten haben, informieren Sie bitte sofort den
Absender und vernichten Sie diese Mail. Das unerlaubte Kopieren sowie
die unbefugte Weitergabe dieser Mail ist nicht gestattet.
Ueber das Internet versandte E-Mails koennen leicht unter fremden Namen
erstellt oder manipuliert werden. Aus diesem Grunde bitten wir um
Verstaendnis, dass wir zu Ihrem und unserem Schutz die rechtliche
Verbindlichkeit der vorstehenden Erklaerungen und Aeusserungen
ausschliessen.
This E-mail may contain confidential and/or privileged information. If
you are not the intended recipient or have received this E-mail in
error, please notify the sender immediately and destroy this E-mail. Any
unauthorized copying, disclosure or distribution of the material in this
E-mail is strictly forbidden.
E-mails via Internet can easily be prepared or manipulated by third
persons. For this reason we trust you will understand that, for your own
and our protection, we rule out the legal validity of the foregoing
statements and comments.
Reply by ●October 17, 20062006-10-17
On Mon, 16 Oct 2006, Laurent wrote:
> Hi,
>
> I know it is not a good thing to do overclocking, but i am wondering
> how bad it is to go around 2% above the recommended max frequency (
> 266 to 271 MHz in my case ), this is for a SHARC 21375. I am sure it
> is not a good practice, but i expect the safety margin to be more than
> +2% ?
>
> What do you think ?
Make sure you have several devices to try it with. Chances are good it
will work on some and fail on others, and the failure will be "soft", i.e.
hard to detect at first. It's not so much safety margin as it is process
margin - there are going to be transistors which simply can not handle the
speed and they will be flakey, and intermitently depending on everything
that is going on around them. If you can add extra cooling you'll get
better results. Definitly worth a try!
Patience, persistence, truth,
Dr. mike
> Hi,
>
> I know it is not a good thing to do overclocking, but i am wondering
> how bad it is to go around 2% above the recommended max frequency (
> 266 to 271 MHz in my case ), this is for a SHARC 21375. I am sure it
> is not a good practice, but i expect the safety margin to be more than
> +2% ?
>
> What do you think ?
Make sure you have several devices to try it with. Chances are good it
will work on some and fail on others, and the failure will be "soft", i.e.
hard to detect at first. It's not so much safety margin as it is process
margin - there are going to be transistors which simply can not handle the
speed and they will be flakey, and intermitently depending on everything
that is going on around them. If you can add extra cooling you'll get
better results. Definitly worth a try!
Patience, persistence, truth,
Dr. mike
