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Powerbook 520c aftermarket 32mb ram solutions
- Thread starter Motu
- Start date
Nope. None exist because the connector is unobtainium, sadly.
If it has empty pads, yes. I’ve modified 2 this way.
It depends on the actual RAM card. Most of them take 28 pin TSOP chips and the RAM is just regular FPM RAM that you can harvest from 72pin SIMMs.
A couple of examples for you:
I had one 4MB card that was populated with low density 512k chips on one side. I removed them, adding 2MB chips on both sides to get to 32MB. The low and high density chips are wired up slightly differently (the RAS and Write Enable pins are jumbled, and there is additional address line on the higher density chip) so in order for the upgrade to work, I had to change some jumpers on the card to reconfigure it. The jumpers are there since presumably the manufacturer wanted to sell cards with both types of chip on a universal PCB layout.
Here are before and after photos:
I have a couple of Apple supplied 8MB cards which use the low density chips. I’ve looked into replacing them with high density chips, but these cards don’t have any jumpers so I would have to cut traces and add bodge wires in. It’s doable but a bit too much work:
A couple of examples for you:
I had one 4MB card that was populated with low density 512k chips on one side. I removed them, adding 2MB chips on both sides to get to 32MB. The low and high density chips are wired up slightly differently (the RAS and Write Enable pins are jumbled, and there is additional address line on the higher density chip) so in order for the upgrade to work, I had to change some jumpers on the card to reconfigure it. The jumpers are there since presumably the manufacturer wanted to sell cards with both types of chip on a universal PCB layout.
Here are before and after photos:
I have a couple of Apple supplied 8MB cards which use the low density chips. I’ve looked into replacing them with high density chips, but these cards don’t have any jumpers so I would have to cut traces and add bodge wires in. It’s doable but a bit too much work:
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Also, see my YouTube video:
This was for an 8MB card which already had high density chips, so no reconfiguring was required.
This was for an 8MB card which already had high density chips, so no reconfiguring was required.
Let us know how you get on!
My 16MB module is a bit unusual. No obvious brand, though the chips themselves are Motorola. I've wanted to upgrade it since people started experimenting, but it's so different from everyone else's, and I was unable to find a match for the chips that are already there. As it is, it has 8 chips, with 8 slots free, so 2MB per chip present, plus some bus logic it would appear.
EDIT: Correction.
EDIT: Correction.
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Huh, those chips are very common, even more so than the ones on my cards. I just did a quick eBay search for a 16MB 72-pin SIMM and this was the first result that came up.
I’ve seen them on larger 30-pin SIMMs as well.
Obviously these chips aren’t thin package, but if you trim the legs down (I used a dremel) they’ll sit close enough to the PCB that they won’t foul anything.
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Best bet is probably to find them on a contemporary laptop RAM card.
My IIsi had thin package chips, it's no longer in my possession though.
My IIsi had thin package chips, it's no longer in my possession though.
@Iesca
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Yeah, that could take a lifetime to find! No problem functionally to mix and match brands (assuming same spec), but I do understand your perspective.
I suppose I could have double-checked the datasheets for each brand to ensure that they were pin-identical, but it'll probably be fine.
