T43 network IC replacement

[t43_guy]

Hello all, I have been reading these forums for 3 years now but I finally decided to join, thanks for this service guys.

TL;DR: will my T43 recognize the MAC address of the new BCM5751M or will it refuse to POST ?

I have an intel based T43 which I bought non-operational and slowly repaired the motherboard using parts from my other dead T43s, the last thing pending for a fix is the ethernet which currently only works sometimes (maybe for 24 hours or so after the computer has been turned on), after that it starts to misbehave and shows a lot of RX and TX errors, the workaround is disabling it in the BIOS. Now, I did some diagnosing and I'm fairly sure the problem is that the network IC, which is the Broadcom BCM5751M, is faulty, so I have to replace it, my problem is not getting a replacement since I have plenty of donor T43 motherboards, but rather that I'm not sure as if replacing this IC will make the machine unable to POST because this new IC has a different MAC address and thinkpads are quite picky when it comes to unique identifiers.

The network IC is connected to an EEPROM which is U33 (located near the broadcom IC) which holds some data that I'm not sure what it actually is, but from reading datasheets from other Broadcom ICs I think it only holds the PXE code and the device and vendor IDs which one can see issuing lspci on Linux, so there should be no problem in changing the broadcom IC because it contains its MAC and the BIOS should read the new MAC from it (?).

My question is, can I replace this IC and the machine will work as usual, using the new MAC address ?

Maybe someone here has experience about replacing network ICs in a thinkpad. Also I would appreciate if you can provide a link to the BCM5751M datasheet, I searched as much as I could but it seems that it isn't available online as it is a very old IC.

[ajkula66]

Welcome to the forum!

The LAN card is integrated into the motherboard and is not meant to be replaced.

Getting a PCMCIA LAN adapter would be my advice.

Good luck.

[t43_guy]

Yeah, I thought about a PCMCIA card but I want gigabit speeds :s
and gigabit Express cards are hard to find and expensive so I want to fix this thing

Thanks for your reply anyways

[ajkula66]

Yeah, I thought about a PCMCIA card but I want gigabit speeds :s
and gigabit Express cards are hard to find and expensive so I want to fix this thing

$6.99 on Amazon...

https://www.amazon.com/NETGEAR-GA511-Gi ... B0002VITFU

I love the T4x generation but would advise anyone against dumping too much time and/or money into that platform nowadays.

YMMV

[RealBlackStuff]

You didn't search very much I guess (or used that crappy Google)
Use DuckDuckGo to search for: BCM5751M datasheet
The very first link is a PDF.

And then read this: /viewtopic.php?p=717184#p717184

[BillMorrow]

how will you get anything into venezuela..?
just asking..

also, i don't know what "LA" means where you are but please edit your location to show where you are..
unless, that is, your government is watching and not approving..

[t43_guy]

Yes, you are right RBS, but that is not a datasheet, it's a product brief and doesn't tell me what I need, I already removed the chip from another T43 and I'm just waiting to buy the BGA solder balls but I don't know their diameter, I'm gonna go for 0.4 mm and hope that works.

EDIT: I read the whole post you linked but I couldn't make any conclusions, I guess if the thinkpad complains I will replace the EEPROM as well lol

[t43_guy]

oops sorry, I don't like disclosing my location publicly but I just noticed that it now shows up in my profile, I will change it now.

[kfzhu1229]

oops sorry, I don't like disclosing my location publicly but I just noticed that it now shows up in my profile, I will change it now.

I believe a rule on this forum is you must show your actual location, the reason why is to prevent spams (whether your IP address is in the blacklist of suspected bots or not for example).
The network IC on these things are in a BGA package. Replacing it means you have to reball and unless you are dealing with a T43p motherboard with FireGL graphics, it is simply not worth your time to perform a reball on especially the Intel iGPU motherboard.