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Powerbook 520c aftermarket 32mb ram solutions

Posted by: Motu on 2024-06-11 00:12:45

Are there any aftermarket 32mb ram solutions - kits etc. to suit a Powerbook 520c 'Blackbird'

Posted by: croissantking on 2024-06-11 11:00:20

Nope. None exist because the connector is unobtainium, sadly.

Posted by: Motu on 2024-06-11 14:54:57

Thanks for the reply,

Could a current 8mb card be modified to support 32mb?

Posted by: croissantking on 2024-06-11 14:55:51

Thanks for the reply,

Could a current 8mb card be modified to support 32mb?

If it has empty pads, yes. I’ve modified 2 this way.

Posted by: Motu on 2024-06-11 15:02:57

Could chips be removed and replaced with others to create 32mb?

What type of chips are compatible?

Posted by: croissantking on 2024-06-11 17:57:05

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:

Posted by: croissantking on 2024-06-11 18:08:42

Also, see my YouTube video:

This was for an 8MB card which already had high density chips, so no reconfiguring was required.

Posted by: Motu on 2024-06-11 18:12:04

Ok that sounds like really great news.
Thanks croissantking I will check out what brand 8mb card I have, do a bit more research and go from there.

Much appreciated for the info

Thank you

Posted by: croissantking on 2024-06-11 18:44:02

Let us know how you get on!

Posted by: Motu on 2024-06-11 18:48:58

Will do, I am quite excited about this. Might take a bit to source all the required bits and pieces. I will keep you posted.
Thanks again
croissantking 🙂

Posted by: Iesca on 2024-06-11 19:51:15

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.

Posted by: Motu on 2024-06-11 20:09:59

Hi Iesca,

Yes yours does look quite different.

I will get some pictures of my 8mb card and post them up here.

Thank you for posting

Posted by: croissantking on 2024-06-12 01:34:14

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.

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.

Posted by: Iesca on 2024-06-12 02:37:37

Yes, it was the thin-package ones specifically that I was having trouble finding. I'll take a look though!

Posted by: croissantking on 2024-06-12 02:47:16

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.

Posted by: croissantking on 2024-06-12 04:21:42

@Iesca

EDO SIMM RAM Speicher für Apple Power Macintosh 8100 8150 | eBay

EDO SIMM RAM Speicher für Apple Power Macintosh 8100 8150 usw. zu verkaufen. Zustand und Lieferumfang siehe Fotos. <p dir="ltr" style="margin-top:0...

www.ebay.co.uk

Posted by: Iesca on 2024-06-14 21:54:30

I was looking for exact matches with the particular Motorola chip on my RAM card, but I suppose beggars can't be choosers, I'll give it a shot. Thanks for the link!

Posted by: croissantking on 2024-06-15 02:44:12

I was looking for exact matches with the particular Motorola chip on my RAM card, but I suppose beggars can't be choosers, I'll give it a shot. Thanks for the link!

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.

Posted by: Iesca on 2024-06-15 02:46:38

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.

Posted by: Motu on 2024-06-18 09:04:09

This is the ram module I have in my powerbook 520c.

Will I be able to find replacement chips for it to modify it to 32mb?

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