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Powerbook 1400 16mb ram module upgrade to 24mb
Posted by: surfer150 on 2024-05-20 10:07:27
Also, I note there seem two be two different offsets on your card for each RAM chip. I also note that you've installed the donor chips differently from the factory ones. I am not sure if the offset pads are just to accomodate different sized chips or if it's for some other reason. It's worth investigating -- personally, I would have positioned the new chips the same as the originals.
Thanks for the information. Will investigate that.
Posted by: surfer150 on 2024-05-20 10:12:35
Checked this, there’s only one way mounting the chips
Posted by: croissantking on 2024-05-20 10:15:18
Checked this, there’s only one way mounting the chips
OK, cool. Maybe add some flux and try reflowing the connections on the donor chips. Also, use a multimeter to make sure there are no neighbouring pins shorted to each other. Failing all of that, I would try a different set of donor chips.
Posted by: surfer150 on 2024-05-20 10:22:23
I now tried an entirely different set of donor chips (i ordered 10 pcs) but still same result. The RAM error is not present anymore but still only 16 instead of the full 24 MB are recognized.

Maybe it has something to do with this missing resistor? But this is unlikely as then Pin 1 (5V) of one chip would he shorted against Pin 28 (GND) of the other chip.
Posted by: Snial on 2024-05-20 11:08:37
I have to admit that I'm still kind of confused by your explanation. Are you saying that some 16MB RAM cards are made up of only 4x4MB chips? Because I'm pretty sure that the 16MB RAM cards which use 28-pin TSOP chips, like @surfer150 's, are all composed of 8x2MB chips. I have never seen a 4MB chip in this form factor.
It would help a lot if I read things properly. I thought 4MB x 8 was possible, because 2M x 8 is possible, but the developer note only says that it supports 2M x 8 and 4M x 4. These are also 2MB chips. Nevertheless, it takes 8 x 4Mb x 4 to make 32-bit wide memory, and this also leads to a single bank of 16MB of RAM. Adding another 4 x 4M x 4 wouldn't work.

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Hmm, a bit below, it says the PB 1400 also supports 1M x 16 chips, which again are 2MB chips, but only need 2 to provide 4MB of RAM.

2M x 8 is different. We still need 4 of them to create 32-bit memory, giving 8MB, so a 16MB card containing these chips will be organised as 2 banks, and another 4 chips give another bank making it up to 24MB.

Ultimately, it's the number of address pins on a chip which determines if 16MB is 1 bank or 2: any 4M x anything leads to a single 16MB bank and 24MB isn't possible on the same card. 2M x anything leads to a multiple of 8MB banks.

Sorry about my lack of experience with actual memory cards (which might not ever use 4M x anything DRAM); I was just going from the developer notes. And I misread it, but I think my conclusion still holds even if real memory cards never used 4M x anything chips.
Posted by: surfer150 on 2024-06-01 13:19:51
The chips have arrived from the UK and I tried the same now with my G3 Kanga and exactly same issue. The newly soldered chips are not recognized, I’m still having only 128 MB RAM instead of 160 MB.

Conclusion: It is not possible to upgrade any PowerBook RAM card by soldering additional chips on it.
Posted by: croissantking on 2024-06-01 13:27:04
Conclusion: It is not possible to upgrade any PowerBook RAM card by soldering additional chips on it.
It’s absolutely possible in most cases. I have maxed out numerous cards for PowerBooks 1400 series, 500 series and 100 series.
Posted by: surfer150 on 2024-06-01 13:36:56
Maybe you had just luck with your modules.
Posted by: croissantking on 2024-06-01 13:41:33
Maybe I could have a play with your 1400 series modules and see what’s going on.

I’m convinced it’s upgradeable and something else is going on here.

About the Kanga I have no idea, I don’t have one of those machines. Though I did upgrade a PB3400c 16MB module to 32mb for @mg.man , not sure if he’s tested it yet.
Posted by: mg.man on 2024-06-01 15:43:15
I did upgrade a PB3400c 16MB module to 32mb for @mg.man , not sure if he’s tested it yet.
I have not. My 3400Cs are all in bits. I'll try to find time to put one (mostly) together and check out @croissantking's wizardry. The 180c card he populated for me works great! 🙂
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