Replacing the T40 -1 Banias CPU with the T42 Dothan CPU

[poshgeordie]

Increasingly I'm being asked to provide refurbished T4x's with upgraded CPU's, so this has come from that.

One of the best ways of increasing the performance of a T40, T41, or R5x, is to replace the existing CPU with an uprated one from the T42 series.

Both series uses the Socket 479 Intel Pentium M series with the 400MT/s (Mega Transfer/second) Front Side Bus.

The T40-1 and R5x uses the slower Banias series chips with 1MB cache, whereas the T42 uses the faster Dothan series with 2MB cache.
In reality there is an appreciable speed increase with the Dothan chip and it is a drop in replacement for the Banias one.

The only other thing that needs replacing is the stock Short Fan Assembly 91P8393 with the uprated Fan Assembly 26R7860. The M10 Long Fan Assembly from the "p" series 13R2657 can be used too.
I'm not sure if the other Long Fan Assembly 13N5442 can be used, since I suspect it's for Banias chipped p series - can someone confirm please.

The following table lists the Banias chip series followed by the equivalent Dothan, and is in the form:

Banias || Dothan:
Pentium M 1.4 SL6F8 || Pentium M 705 SL7V5
Pentium M 1.5 SL6F9 || Pentium M 715 SL7GL
Pentium M 1.6 SL6FA || Pentium M 725 SL7EG
Pentium M 1.7 SL6N5 || Pentium M 735 SL7EP

Then it's Dothan from here on:
Pentium M 1.8 aka M 745 SL7EN
Pentium M 2.0 aka M 755 SL7EM
Pentium M 2.1 aka M 765 SL7V3.

The Dothan chips start out very cheap second hand but get a little more expensive as the speed increases.

Further information on the chip types can be seen on this wiki.

There are many more chip numbers listed, however the ones I've listed are the ones that will be readily available in practice.
The full list is in post #4 - thanks to RealBlackStuff.

Also please note that only those Banias processors with a Dothan equivalent are listed. For instance the Banias Pentium M 1.3 isn't shown.

Can someone check I've got the information correct and post back any changes etc needed.

<EDIT> Added R5x - Thanks HarryC
<EDIT> Added Pentium M 1.4 equivalents - Thanks RealBlackStuff

[Harryc]

Nick, your list looks correct to me. I've used 1.7Ghz Dothan (Pentium M 735) CPU's in T4X machines (and R5X's) many times, so that is another option.

[underclocker]

Very nice service...I upgrade most of my T4x machines to 1.7 Dothans, they do seem snappier.

Any T4x fan will work with any T4x machine, whether or not the T40p long fan is "optimal" is the issue. It's probably good, but the later designs had a little more copper over the GPU.

The CPU upgrade does not require a fan upgrade. Some people on the forum argue that the long fan is better for all ATI GPU's. I have never "upgraded" the fan on any ATI 7500 machine, even with an upgraded CPU and a swapped SXGA+ LCD. I haven't seen any ill effect. That being said, I do not think the long fan will hurt! I believe the long fan was provided with every ATI GPU except the ATI 7500 (on T4x's).

FYI, production of the R51's overlapped with the T42's, many originally came with Dothan CPU's. Also, while the ATI T40/T41/T42/R50/R51's use the same BIOS and EC, the Intel GPU based R51's used different BIOS and EC, they also support a few more CPU's than the ATI GPU mobo's (like the Dothan 725A, Dothan 735A, etc.)

[RealBlackStuff]

You are missing quite a few models!

All Banias with 1MB cache and FSB 400:
Pentium M 1.3 SL6N8 / SL6N4 1300 MHz
Pentium M 1.4 SL6F5 / SL6F8 1400 MHz
Pentium M 1.5 SL6F6 / SL6F9 1500 MHz
Pentium M 1.6 SL6F7 / SL6FA 1600 MHz
Pentium M 1.7 SL6N9 / SL6N5 1700 MHz


All Dothan with 2MB cache and FSB 400:
Pentium M 710 SL7V5 1400 MHz
Pentium M 715 SL7GK / SL7GL 1500 MHz
Pentium M 715A SL89U 1500 MHz
Pentium M 725 SL7F2 / SL7EG 1600 MHz
Pentium M 725A SL89T 1600 MHz
Pentium M 735 SL7ER / SL7EP 1700 MHz
Pentium M 735A SL7BA / SL7EQ 1700 MHz
Pentium M 745 SL8U8 / SL7EN / SL8U6 1800 MHz
Pentium M 745A SL8QZ 1800 MHz
Pentium M 755 SL7EL / SL7EM 2000 MHz
Pentium M 765 SL7UZ / SL7V3 2100 MHz

Another thing to remember:
Dothans with ODD numbers (e.g. 715/725/735) have a 400 FSB (except the 710, which is also 400! Intel wouldn't be Intel...)
Dothans with EVEN numbers (e.g. 720/730/740) have a 533 FSB

[poshgeordie]

I'm glad you mention the long fan - personally I don't really see the point of using a long fan with a gfx chip that doesn't require it, especially for chips like the 7500 where the gfx part of the heatsink doesn't even touch the top of the chip because the chip isn't high enough.

I would even argue that a 7500 gfx chip (for instance) will in fact become even hotter in the presence of the long fan, due to restriction of an already restricted air flow.

I posted the FRU's to preempt anyone asking if they can be used.

Thanks for that information on R5x's - I have no knowledge of them so it completes more of the picture.

[poshgeordie]

@RBS - I didn't put those part numbers in because they don't appear to be readily available (via eBay yesterday anyway!) so I thought I'd leve them out to keep it simpler.

I do take your point though and thanks for pointing it out - do you think they are readily available in fact?

[lifrancis]

For all those people interested in such a transplant operation, there is a guy on ebay selling brand new Intel® Pentium® M 735 Centrino1.7GHz/2M/400 SL7EP for $20. The shipping cost is more than reasonable too.
http://cgi.ebay.ca/ws/eBayISAPI.dll?Vie ... 0328491536

[t140568]

Can the fans from a T4x be swapped to an R5x too, or just the processor?

[poshgeordie]

No, the R5x fan designs are different to the T4x ones.

[underclocker]

I believe the T4x fans will fit in R5x machines. Also, at least one forum member has used an R5x fan in a 15" T4x machine. R5x fans won't fit in 14" T4x cases since R5x fan casings are slightly thicker.

The power connector and voltage is the same/similar for all, so they will any will spin up properly in any machine.

However, fan/cooling design is closely engineered to case design. Since the T4x and R5x machine have different cases, it is probably not advised to swap fans.

Of course, if you're comfortable with monitoring temps and testing out new solutions, please let us know what you find!

[t140568]

Just ordered a 26R7860 from eBay for $9. We'll see how it goes. ...and, thinking about it, I need thermal paste...

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