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Can I downgrade my Core 2 Duo Laptop Processor?

We have a few newer dell laptops...the Latitude D630's.  They have the Core 2 Duo T7300 processors, and I am wondering if I can simply take the laptop apart and replace the processors?  The Core 2 Duo processors have issues with some of our older software tools and I would like to downgrade them to a Pentium D or Pentium 4 processor.  I know with our older laptops (Pentium III's, Pentium M's) you could change the processors, but I am not sure about the newer Core 2 Duo's.  Also, maybe the chipsets and sockets are different and maybe they ONLY accept core 2 duo's?

Thanks for any advice.
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jasin00

what are your older software written for?? 16 bit? instead of switching out the proc's which is a bad idea. have you tried a different O\s?? you'll have to check with dell but most duo m\b can handle a p\4. dual boot the system with unbunto 7.10 will those tools work in linux?
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No, we need to keep windows.  The software is an older version of Matlab (engineering software)
try installing a second hdd with a fat 16 file system. core duo are basically pentiums stacked on top of each other what kind of issues are you having with your software?
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We have Pentium 4's with Hyper Threading and Pentium D's that run Matlab just fine.  On the Core 2 duo machines with the software problem, we have even disabled the dual core processing in the Bios and it it still has the problem.  I don't think the fat 16 is the problem.  Getting into the software issues are a bit complicated, but when Matlab is running regressions and streaming data through a serial port, it locks up the process and we have to kill the Matlab application.  As I mentioned, this process works fine on P4's with Hyper Threading and Pentium D's.  Something about the Core 2 Duo that causes problems.  The version of Matlab we are running is quite old and un-supported.
You can downgrade to CPU P4 on Dell D630's. Did you try Matlab on desktop PCs which have Core 2 Duo cpus?

I dont know about old version of Matlab, but it is running fine with current version on market.
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"... core duo are basically pentiums stacked on top of each other ..." => Not at all true.   The Core architecture CPU's are significantly different architecturally then the Netburst architecture of the Pentiums..

"... You can downgrade to CPU P4 ..." ==>  Not according to Intel's documentation.

Intel's documentation for the GM965 Express chipset does not list any Pentium IV's among the supported processors --> so you can't downgrade to a Pentium 4.

Your comment that the system hangs "... when Matlab is running regressions and streaming data through a serial port ..." is interesting.   Does Matlab work okay if you are NOT streaming through the serial port?   If so, then the issue is most likely not the CPU, but the configuration of the serial port.

I doubt that you need to disable the dual core processing ... if this was an issue with using dual cores (which you could resolve by simply setting processor affinity without needing to disable the 2nd core) then you would almost certainly have the same issue with hyperthreading enabled on your Pentium IV's and with your Pentium-D's.

Are you using the same OS on all systems?

... I have a couple of other thoughts you can try => but first confirm whether or not Matlab works okay if you are NOT streaming data.
Oh, that is typo .... I meant "can not downgrade" not "can downgrade" ... :o)
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Thanks for the input so far.  To answer some of the questions, we are all using Windows XP Pro SVP2.  Matlab seems to work fine (on a Core 2 duo) when doing other task...it just hangs on the regression tests when streaming data over the serial port.  We did set the processor affinity and disable the 2nd core in bios, but that didn't make a difference...and like garycase said, it works fine on our hyperthreaded machines and pentium dual cores.  It seems to me that the difference in the chip architecture is really the only difference.  We did actually purchase our first Core 2 Duo desktop a month or so ago, and it had the same problem as the dell laptops.  The strange thing is, it took much longer for the desktop system to hang.  What I mean is, the regression test some times take days to complete...on these dell laptop's, the test usually hang within the first 5-10 minutes of the test.  The desktop core 2 duo worked for quite a few hours before it hung.  

I think serial port configuration is fairly straight forward, isn't it?  I mean, we make sure all the settings are set the same (as they are in the P4 and Pentium D's) and the regression test do work and stream data for a few minutes...they just end up hanging after some random time...5-10 minutes on the laptops and usually longer on the desktop.  Hope that helps anwer any questions.

If I can't downgrade the processor, then I think I am going to purchase an AMD equipped laptop next and see how that handles this process.
... so basically Matlab works fine in terms of its computational abilities => this means you can enable the dual cores; don't need to set processor affinity; etc. ... and should thus be able to get the benefits of the Core-based architecture's performance.

The issue seems more likely to be something associated with the newer systems' serial ports.   Are there any alternative ways to stream your regression data -- i.e. via ethernet (best) or with a USB->serial converter (this may be more reliable on a newer system) ??   What baud rates are you using on the serial ports?   Full handshaking?  9-wire cables?

... Moving to an AMD system will not only give you much lower performance; but it's also not clear this will resolve this issue if it's indeed related to the serial communications.
If it's a laptop and you are having problems with heavy computational programs (regressions), your cpu may be overheating.  Laptops in general can get very hot under normal use, and if you drive them at 100% cpu, they may not be able to stay cool.  Theoretically, Core2 Duos should step down in speed when this happens, but it seems odd that it only happens when you put it under load.  Try blowing out the vents or using a cooling plate; I have not heard of software that works on Pentiums but won't work on Core2 Duos.
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The thing is, when it's running regressions, the computer is doing VERY little, except sending data (slow data) out the serial port.  It's not a heavy burden at all on the system.  It's just a guess that the core 2 duo processor is the problem.  That's the only thing that is different about the computers really.  They all have the same software load, 2GB of memory, etc.

One interested thing is that Core 2 duo's seem to have some chip bugs.  See this wikipedia link:  http://en.wikipedia.org/wiki/Intel_Core_2 and look at the section called chip bugs.  One sentance states that "in rare instances, improper TLB invalidation may result in unpredictable system behavior, such as hangs or incorrect data."  I found a Windows patch called KB936357-v2 but that didn't make a difference in our scenario.
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The thing is, when it's running regressions, the computer is doing VERY little, except sending data (slow data) out the serial port.  It's not a heavy burden at all on the system.  It's just a guess that the core 2 duo processor is the problem.  That's the only thing that is different about the computers really.  They all have the same software load, 2GB of memory, etc.

One interesting thing is that Core 2 duo's seem to have some chip bugs.  See this wikipedia link:  http://en.wikipedia.org/wiki/Intel_Core_2 and look at the section called chip bugs.  One sentance states that "in rare instances, improper TLB invalidation may result in unpredictable system behavior, such as hangs or incorrect data."  I found a Windows patch called KB936357-v2 but that didn't make a difference in our scenario.
Heat could indeed be an issue here ... but if the CPU % is low (as you've suggested) it still seems like a serial-port-related issue.

An interesting test ... install Virtual PC on the laptop;  then install XP in a virtual machine and run Matlab in the VM (with the COM1 port directed to the physical serial port).    See if that has the same symptoms.    From Matlab's perspective, this will make the system's chipset look like a 440BX ... which may impact how it treats the communications.
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Callandor
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... as Callandor noted, you could install a Core Duo CPU [Dell shipped the system with both Core Duo's and Core 2 Duo's] ... but I really doubt that will make a difference [I suspect Callandor agrees :-) ].

... Note also that the T7300 does not have the TLB issue (which was an issue on earlier versions of the Core 2's); and since it has hardware virtualization support would work quite nicely with a virtual machine ==> I'd try what I suggested above and see if that makes any difference.
I agree - going to a Core Duo would be in the list of last resorts, and I would be astounded if that actually made a difference (not to mention it would cost money to try).
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Callandor...that's the "almost answer" I am looking for!  An inexpensive way to really find out if the processor is the issue here is to just buy another processor and put it into the laptop.  So, where can I find a boxed processor that is the previous generation?  Looks like a T2XXX series is the Yonah processors.  Are there different sized processors for desktop and laptops?  
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