Thinkpad 701c replacing or removing onboard memory

[x220]

Hello all,

I have a 701c showing error 201, unfortunately this error still shows if the extended memory is removed meaning it's one of the onboard chips that are at fault.

Here are my questions:
1) My 701c has 8MB of onboard memory, is it possible to simply remove 2 of the chips to convert it to a 4MB model or are there other alterations to the motherboard. If so which chips would have to be removed, or is this irrelevant?

2) The expansion memory currently installed has chips with a very similar ID. The onboard RAM is: 0116160CT3C-70, the expansion RAM chips are: 0116160PT3D-70. Would it be possible to locate the faulty onboard memory chip and replace it with one from the extended memory, or would they be incompatible.

3) When the memory test is conducted I am given the address of where the fault is found, is it possible to determine which of the onboard chips are at fault from the address (I haven't got it at hand unfortunately)

Cheers
Jim

[mnowell69]

i had the same problem with my 701c, and when i looked closely at the planar, there was a resistor (or similar chip) that had broken away between the memory chips. As it was too small for me to solder, i had to buy another planar.

[x220]

Hello, thanks for the advice.

Sorry for the ignorance, what do you mean by the 'planar', having a bit of a thick headed day

Edit: Never mind, google states that a Planar is another name for a motherbaord used by IBM

[aPanzerIV]

Hello,

My grandfather has a 701C that I've been working on.

It has a problem with the onboard ram too, but he also has a 16mb chip in the expansion slot.

Would it be possible to disable usage of the onboard chip in the bios?

If not can we simply de-solder the modules? Someone got a picture of a 4mb/8mb models side by side for comparison?

[micrex22]

Unfortunately many IBMs (not just IBM thinkpads) access the onboard memory banks first and sometimes specifically look for them. If you remove the onboard memory on say a TransNote, the system won't POST without them; the same may be true for the 701C, I'm not sure.

There is no function to disable onboard memory whatsoever.

Possible options:

#1 purchasing a replacement system board "planar" (I have a bunch still factory sealed and used spares, but not sure if I'm ready to part with them just yet)
#2 desoldering the memory chips and replacing them with equivalents-- if this route is taken, be sure to desolder all of the memory modules and see if the system will still POST without them. I might actually test removing all of the memory modules on one of my boards which has bad onboard memory.
#3 troubleshoot to see if the issue is something else on the board (such as a resistor as another poster wrote)

[rkawakami]

@micrex22: Welcome to thinkpads.com!

There is no function to disable onboard memory whatsoever.

This is not universally true. A "hack" was found many years ago on those systems whose BIOS contained a hex editor (e.g, 600-series). By simply editing a byte in the BIOS, the onboard memory was ignored.

[micrex22]

@micrex22: Welcome to thinkpads.com!

There is no function to disable onboard memory whatsoever.

This is not universally true. A "hack" was found many years ago on those systems whose BIOS contained a hex editor (e.g, 600-series). By simply editing a byte in the BIOS, the onboard memory was ignored.

That's true-- I guess anything is possible through editing the BIOS. I should really set aside some time to do extensive 701C breakdowns and modifications; and then document it for posterity.