72-pin SIMM injection for updated SE/30 Schematic?

[Trash80toHP_Mini]

Yep, mentioned doing just that a few posts above. I've got a 72-pin 16MB SIMM with eight TSOP ICs, 32 of which might easily be arranged on top a/0 bottom of the existing SIMM outline. Not thinking about that so much however, not everyone would necessarily want all 128MB. It would be a massive PITA to offer more than one config or to upgrade with more ICs thereafter. Besides, a compact Mac IIx really needs to have SIMMs of some type on board. []

This project is being done, period. My working SE/30 has a broken clip on the rearward bank. Those 30-pin sockets will be coming out. They will be replaced by header pins of the proper number (less than 120) for sockets under an adapter with 72-pin socket aboveboard.  [}]

72-pin socket will be located in the centered for minimal footprint and clearance in the /30.



IIRC this is the solder side of a SIMMsaver I'd scanned in a previous incarnation of this insanity. ATM, I've another in my hand that's been stripped of components. Let the games begin!

 

[Trash80toHP_Mini]

Bumping because the idea for this popped up in another thread. Also wanna vent my frustrations about lack of desoldering skills! Made a mess of desoldering a horizontal 72-pin SIMM socket and not quite a horrible a mess of the EuroDIN connector on a redundant Reply board.

Has anyone seen a video about using a 100% Chitanium Clone of the proper vacuum  pump desoldering station from the folks at Hakko?

 

[Trash80toHP_Mini]

Anyway, a 16M bank can be 10 X 12, 11 X 11 or 12 X 10, in theory.   A 64 MB bank must be 12 X 12.  

The Quadras were seeing 64MB SIMMs as 16MB, because they were ignoring a couple of the address bits. 

The Quadras were hamstrung by those address bits being siphoned off to service the measly 4MB on the board. Dunno about the SE/30 but that's the way of the IIsi setup I've got posted in an earlier thread. I'm a bit fuzzy at this time of morning, but ISTR it's just a pair of address lines that need to be hotwired from the memory controller service a 64MB daughtercard replacement for Bank A. Not as easy in the IIsi as itt's the first machine Apple chose to hobble with SMT memory for Bank A as it did in the Q630 series.

It's not that the Quadras can't "see" the "address bits" (RAS lines ISTR) as they're just not there. Back in the DR. Bob era of 'fritter, someone linked to a Quadra 605 128MB hack done along the lines of my IIsi hack that he dubbed the "Evil RAS line hack" if memory serves.

 

[Trash80toHP_Mini]

@trag found the relevant thread: SIMMspender™ & IIsi memory expansion hack reboot.

Three lines from MDU to Bank A of the IIsi are unimplemented and in need of hotwiring to support 64MB in a 72pin SIMM adapter.

View attachment 22394

Thinking same is true of Q630, Q605 and others hobbled by 4MB of soldered DRAM. Thinking would be that hotwiring these signals from excised chip logic board memory pads to the hobbled slot of the twin slot 630 would do the trick easily. Single slot 630 and 605 machines would be evil, but doable.

 

[Kai Robinson]

Hmm. I've been thinking about this. Rather than using DRAM/SRAM - it'd be easier (and cheaper) to remove the simm sockets entirely, and solder in a replacement memory board, based on SDRAM, using a CPLD. If the TF536 board can make an Amiga run with 64MB of cheap (like, £3 a piece) SDRAM, i'm sure an SE/30 would be doable. If the sources are ever released, it'd be easy to use that portion of the XC95288XL CPLD on the TF board, in a memory expansion board.

 

[Trash80toHP_Mini]

Dunno, desoldering the SIMM sockets and replacing them with an adapter board for a 64MB SIMM would be KISS compliant. It's the reverse function of the bog simple 30pin SIMM Saver. No need for the complications of CPLD implementation. Adding memory to the logic board in lieu of SIMMs is one thing, but an adapter board for the stock SE/30 hasn't got the area to spare for mounting anything but a 72pin SIMM socket and even that exceeds the footprint of a 30pin SIMM quartet. The adapter board needs be riddled with thruhole headers to be installed into SIP sockets installed in the thruholes of the excised 30pin SIMMs.

Here's the most recent design study. I need to rework it now that @trag has made it clear that a pair of 32MB SIMMs won't work in this config:

View attachment 2788

One SIMM has to go and I'll need to align the edge of the remaining 72pin socket with the 30pin sockets so that the excess PCB overhangs the 68882. So probably no room for SMT memory in a refit, but not a bad idea at all for an updated SE/30 board.