Simm Saver 30

[unity]

Picked up a couple of these. I remember using them years ago in an SE or Classic maybe. I don't recall. But I do not recall if they let one "bypass" the theoretical limits of the hardware. For example, an SE/30 can address a whopping 128MB of RAM. But the processor can, technically, address up to 4GB. So would stuffing eight of these bad boys with 16MB SIMMs allow 512MB of RAM?

 

[mcdermd]

I think you would need to mount the logic board externally.

 

[Trash80toHP_Mini]

Got piccies? Close-ups of both sides would be dynamite!

I saw something like that on eBay, but never did pull the trigger. I wasn't absolutely positive what it was. It might be similar to something I've been working on for the IIsi, but four would be required. Jumper the Bank Select lines and decode four 72pin SIMMs as four banks of four 30 pin SIMMs from the MoBo's 30pin sockets.

I'm not sure you can get something like that to work in a compact, but for systems capable of addressing whatever amount of RAM you put in it, you ought to be good to go. Compact Virtual might even make it work for the Compacts, dunno, the only time I've seen that work was on an Accelerator.

 

[unity]

I think you would need to mount the logic board externally.

Ya.. it would be more for a test drive than practical use! I am going to try to find two more. I may even have more in storage, I really don't recall. New 60ns 16MB SIMMs are only $10 each new. So $80 would load up the two I have. Tempted.

Oh, pics! Duh! lol

 

[Trash80toHP_Mini]

Yep, pretty big ! :lol: Did you get four? I like the notion of decoding a single 72pin SIMM funneled into in each 30pin socket better than doing four 30pin SIMMs, much more compact!

 

[unity]

Yep, pretty big ! :lol: Did you get four? I like the notion of decoding a single 72pin SIMM funneled into in each 30pin socket better than doing four 30pin SIMMs, much more compact!

I got two from eBay. Price was a little high maybe at $35 for the pair, but I splurged a little. Its harder to find 30 to 30 pin. I agree, a 72 pinn into a 30 would be slick and much more practical! But for now, this is something I can tinker with. Problem is I have too many compacts and no II series in hand with a 68030. The 68020 can only address 16MB of RAM, I think.

 

[redrouteone]

I would be really surprised if the processor had all of the address pins needed to address 4GB of RAM.

My guess is that 128MB is the memory limit as that is the limit of the address lines on the motherboard, and I would likely say the 68030 would only have enough addresses pins for that also.

 

[Trash80toHP_Mini]

Is that the max for the IIci and the SE/30? IIRC they've got the same memory controller as the IIsi. Might need to go with Virtual Memory on the IIsi, even if I can implement all four banks. Two should be fairly easily accomplished anyway. [}] ]'>

 

[techknight]

it doesnt. 32-bit processors can ONLY address 4GB. And thats the full address map end to end.

Macs, and any computer in general has addressing for ROM, peripherals, interrupts, and other stuff.

4GB is assuming its all RAM from end to end, which isnt possible for obvious reasons, you would have no memory mapped I/O! Newer CPUs have physical address extensions that can handle more than 4GB of addressing but I have no idea how that works, other than the fact that it extends addressing above 32 bit.

 

[Trash80toHP_Mini]

Ye olde High Memory hack? :lol:

edit: I knew I should have kept my trap shut about the SIMM Spender Hack. The SE/30, IIci and IIsi all have just the two banks of RAM, but each Bank can address 64MB. I get confused every time I when I read: "4-SIMM banks of 80ns 30-pin memory" over on LEM. That should read: "2 banks, consisting of 4 80ns 30-pin memory each!"

Dunno, maybe it only confuses me, but it's time for yet another hacks thread! :approve:

 

[olePigeon]

It allowed you to stack smaller, cheaper SIMMs into a single SIMM slot. It still won't let you go over the maximum. I've tried it a few times in both my IIci and Quadra 605, it'd fail to boot or wouldn't see the RAM.