how to disable dimm0 on an ibook 800?
 

hello everyone.
either the 128MB of built-in RAM or a connector or something on dimm0 (the built in slot) on my ibook 800 is broken.
sometimes the computer recognizes the RAM, other times, it just says it is empty. when it recognizes it, the computer usually crashes. when it doesn't, it runs like a dream on just the additional 512MB in the other dimm.

since my computer is way out of warranty, i do not want to take it in to have neither the dimm0 slot repaired, nor have the entire motherboard replaced (which would make no sense economically). i am completely fine with the 512MB of RAM in the other --functional-- dimm.
so what i need to know is:
is there any way (either through software or by tinkering with the hardware) to disable dimm0, so that my ibook will never recognize the faulty 128MB of RAM again?

You might want to investigate whether your iBook is covered by Apples extended warranty for iBooks.

The only other way to tinker with RAM is to take the S0DIMM out - there is no way I am aware of to switch off RAM-banks in software.

Actually, you can disable blocks of RAM in Open Firmware. There was a very detailed article about OF somewhere on the web maybe 12-18 months ago, and it included the commands to do it. I'm not sure if they lasted past a reboot though.

If I can find the article, I'll post the URL.

Most interesting, thanks for the link.

Indeed a great reference ! I didn't know that this much troubleshooting and diagnostics could be done from OF...

Sad that you'll likely see OF replaced by some PC-trash BIOS.

yeah.....but in a pc bios that could be disabled with one click of a button, and not some complicated series of commands, but whatever :rolleyes:

for the user with the problem, are you sure that the original ram is even good? Have you tested it with another system?

what does your system log tell you?

Also, just to play devils advocate here, have you ruled out the possibility of an OS issue? Since OS X is a mutli user, multi tasking OS it limits everything a user does to manage memory. Allocating memory where its needed, and reserving other parts of memory for the system to use. I have seen some cases of an OS corruption that actually occured with memory management parts of it. Causing memory dumps and such from errors. This may not be the case with your ibook, but it could by chance be the problem. Its something I would try. Also, if you do have bad ram, it should error out during an OS load. So, if your system does error out during the OS install then it is highly likely the ram is indeed defective.

It can be disabled with a button, but doesn't necessarily have to be. That is something that has been added. Open firmware can do the same, if so desired.

Unfortunately, I was unable to figure out how to disable DIMM0 from this article. I can limit the size of the ram to something less than the max using the commands provided, yes. But what I really need to do is specify thus:

1. DISABLE the RAM in Slot 1 (built-in).
2. Use ONLY the 512MB of RAM installed in Slot 2.

I tried a few iterations of the commands and looked in the OF guide, but no dice. I've seen at least three iBook G4s with the same problem now. Logic board = OK (except for on-board RAM). I wouldn't be surprised if literally hundreds of iBooks could be resurrected with a clear way to disable DIMM0.

Did you check that ?

Does memtestosx.org come up with errors if you run it with only the onboard memory ?

If you really can't find another solution and the onboard RAM is definitely bad, you can get someone with a SMD rework station and some serious soldering experience take the chips off the Motherboard.

I've figured out how to solve this, after numerous attempts to stop my iBook G4/800 from kernel-panicking basically everywhere (couldn't even get Panther/Tiger installed). My setup was 128MB built-in plus a 512-stick. Panther would panic even with the onboard 128, thus it wasn't the 512 that was at fault. I tried disconnecting the mic, switching HDs, disconnecting the speakers, touchpad, everything, getting down to almost the bare logic board.

In the end I came to the conclusion that it's either the RAM or some failed capacitor or resistor somewhere. I decided to figure out how to disable the RAM. In Open Firmware, you can't specify which module to disable; if you delete the reg entry and only supply the information for your second stick, OF will take the base 128, use it, and only use however much is left from the value you specified from the second stick (so if you had 128 + 512 and specified only 512 as being there, it would take the 128 base and use 384 out of the 512 chip). I had to find a hardware solution. You will have to disassemble your iBook for this, which'll void your warranty, but then again, if you're reading this, chances are you no longer have one :)
There's guides on the net on how to do this, I used this one: http://www.sterpin.net/uk/ddibookg4uk.htm

The theory (supplied by and discussed with a knowledgeable friend of mine) was that, since DRAM usually is in banks, disabling power for one chip (or removing the entire chip altogether) should cause either very very odd results and serious instability, or should cause the entire bank to not be recognized. The latter was correct.

I downloaded a datasheet for a TSOP similar to what is in the iBook (mine had 4 Micron 46V16M16-75s, I used a similar chip from Micron for the pinouts, link: http://download.micron.com/pdf/datas...DDRx4x8x16.pdf, and found that the chip draws its power from pins 1, 18, and 33. I disabled the chip that is closest to the fan, thus to the back of the laptop. If you look at the corners of the chip, the end pins are numbered, more specifically: 1, 33, 34, and 66. You need to disable 1, 18, and 33. I happen to be quite good at soldering, and I used a small needle to push pins upward while heating the pins at the bottom with the soldering iron. Be careful while doing this. You don't want to damage any of the other pins (as to allow for resoldering in case something goes awry), and you really don't want to damage the logic board. Lift the 3 pins so they don't make contact with the pads (use a magnifying glass to check), and tape over the chip with electrician's tape when you're done, just to be safe :)

After this, the first DIMM bank will register as empty, and if you've got no other RAM in there, the iBook won't boot and the sleep light will stay solid, flicker twice, then stay solid again. Throw a good RAM stick in there, and you *should* have a fully functional onboard-RAM-less iBook. Make sure to give it a PRAM reset with Command-Option-P-R. My iBook certainly has stopped panicking, and works perfectly now. I wish you all good luck in fixing yours.

As a note, Apple's Hardware Test found no problems with the onboard RAM.

Here's what it looks like now:
http://img132.imageshack.us/img132/4...cessvc7.th.png

Awesome! Thanks so much for this in-depth description! I will try this on a couple of my dead units.

Disabled Dimm0!!---ok
 

Hi,

I have a PowerBook 12" 1.5Ghz. I Have a problem with DIMM0.
I resolv problem "removing" manualy a memory of logic board..

Its funcionaly!!!..

sorry bad english.....i am brazillian!!.

Tks!!

good look for all

Similar/related post
 

Please see ...

http://forums.macosxhints.com/showthread.php?t=73549

If anyone has any ideas I'd be very glad to hear them.

Thanks.

I'd like to give a big THANK YOU to varu, as I had the exact same problem with my onboard RAM on my iBook G4 1GHZ. Even though I had Hynix RAM chips on the logic board, I disabled pins 1, 18 and 33 on the chip closest to the fan, and the computer now works like a charm with 512MB in the other slot! This post has been incredibly helpful and has resurrected my iBook; for anyone who finds this thread via a Google search (like I did), it's not really that hard if you follow the directions carefully!

The disable chip mod really works!
 

I'd also like to thank those who have left suggestions on this board. I also have an iBook G4 with bad on-board memory. Disabling the pins listed above worked like a champ. It took very little heat from a soldering iron to get the pins to release. Using a sewing needle to pry the pins up works very well.

It should be noted that if you use any of the online disassembly instructions (I like the ones at iFixit.com) you don't really need to disassemble that much of the machine. You only need to remove the bottom cover, and the aluminum shield that covers the logic board. The memory is on the bottom of the logic board, so it's pretty easy to get to. You don't need to remove the keyboard, airport card, or the expansion memory, you only work on the bottom of the machine.

I'm installing Leopard on the machine now, and it's looking good so far.

William in Indiana

Sorry to revive a dormant thread,but while I can follow the instructions here about which pins to disable on the onboard RAM chips, I'm not exactly sure which is which. Does anyone have a good photo of the onboard RAM on an iBook G4 that they could mark up and post here so that I (we -- apparently there's a goodly number of folks with this prob) could see exactly which chip and where we should be operating?

I could open my iBook and take a photo for someone to mark up, if that would help.

Thanks -- It'll save me a 1 GHz 12" iBook.

From varu's post #12 above, it should be the 4 chips marked "Micron" (if you have the same motherboard). Pin 1 should have a round bullet near it indented into the top of the package.

Trevor

Good day Geeks!

I have 3 iBooks G4 2005 with onboard RAM issuse. I can't find on logic board 1, 18 and 33 pins. Could you help me please?

Best regards, please save my computers;)

Unforunately, I didn't get so lucky :(

My iBook G4 1.42GHz has been giving the '3 beeps and 4 sleep light flashes' for the past 3 days. I found this forum and couldn't believe my luck!

Last night, I tried disconnecting pins 1, 18 and 33 from the first chip, but no luck. I completely removed the first chip, still no luck. I ended up removing ALL of the in-built RAM chips (my iBook HAD 512mb of in-built RAM, so that meant 8 x 64mb chips: 4 on the bottom side and 4 on the top side under the RAM expansion slot).

Still no difference, just the 3 beeps and 4 flashes. Time to start looking for a replacement logic board I think. A whole lot cheaper than buying a replacement Macbook for now!

For anyone with an iBook G4
 

I fixed my iBook G4 using Varu's strategy, though I had a different model and a different preliminary situation. Nonetheless, thank you Varu! I couldn't have done it without your help.

I have put together VERY DETAILED documentation of my computer problem, how I fixed it, a tutorial with images on how to disable the appropriate pins, and the resources I used in doing all of this. I posted this file at the following link:

https://xythos.lsu.edu/users/klouth1...nboard_ram.pdf

I hope this helps somebody!

Hey there,
this link:
https://xythos.lsu.edu/users/klouth1...nboard_ram.pdf

provided above by klouth1, seems like it would be really helpful but the link is unfortunately broken.

Any chance of posted it somewhere else? I am eager to try a fix an identical problem with my ibook.

thanks