Breaking the 36MB RAM limit on the LCIII

[-SE40-]

Yes, I dit try to clearefy the idea.
A slot in the pcb may help for stability, and closer positioning of the solderpads, joints.
Ive seen that for 90 degrees pcb montage in stereo’s in the far past……dunno how that works out for 30-45 dergrees. But also depend on how the traces run. So the second guess was that it cuts the traces?

A projector inside is an interresting idea…..how did that project end?

As for the link in my bio, just install pinterest if posible…..its the place where I collect stuff, idea’s and t(h)inker things I like
I was looking for advice on the location for this topic to start my thread on this “Frankenstein” Color-SE40- its still homeless…
(See the introduction page)

 

[Trash80toG4]

A slot in the pcb may help for stability, and closer positioning of the solderpads, joints.
Ive seen that for 90 degrees pcb montage in stereo’s in the far past……dunno how that works out for 30-45 dergrees. But also depend on how the traces run. So the second guess was that it cuts the traces?

You nailed it, trace paths would be impossible to overcome. In an analog system with few traces it would be one thing I guess. The good thing about a surface mount bodge is that the conversion frees up the entire trace side for its contorted flip-flopping.

< tangent >

A projector inside is an interresting idea…..how did that project end?

It hasn't, but it sits proudly on my AppleDisplayUnit awaiting quality optical bench tinker time. 6500 worked fine the last time I touched it what must be ten years ago. Current plexi screen inspired its ChernobylMac code name for development project.

As for the link in my bio, just install pinterest if posible…..its the place where I collect stuff, idea’s and t(h)inker things I like

Can't do that, I've never signed up for anything where personal data can be harvested for nefarious purposes. The policy predates the WWW(ait) by several years. At launch. Given that perspective, at launch I thought Facebook was the dumbest thing I'd ever heard of.

Start a hardware topic detailing your project and I'll be there. Gotta keep this thread on topic.

< /tangent >

 

[-SE40-]

Thanks for your reply, did sent you a PM.

 

[max1zzz]

I was thinking, why stop at two simms when you can have three!

The top slot replaces the onboard bank and would only support single rank simms (Dual rank ones will likely just show as half their capacity)

Really this is just a development stop gap, It's the quickest design I could think of to test if relocating the RAM will cause timing issues (though if it can actually be squeezed into the chassis somewhere this may stay as a permanent variant)

 

[Trash80toG4]

I like it, but still wondering how the memory map works out. Did you catch my PM? The Sonora Memory Controller in the LCIII looks to be Apple's first run at the DRAM control line core of the next gen MEMCjr Controller for Q605/LC475 and related to C610 and C650. So you may be headed toward a hooking up a lot more memory than you think.

It'll be four Banks max as in all previous and later versions. Looks to me like you were hitting on three of four cylinders with that 68MB report.

Does anyone know of a utility that can poll memory and report not just how much there is or if it's good, but will indicate how the memory banks are set up and what memory is located where in those banks?

 

[-SE40-]

Just wondering if there is a simple vertical connector to replace a simslot.
This way it would be easier to expand to memory extension cards ( i call these )
Then it would be simple to plug this card in…..
My two cents

 

[max1zzz]

Just wondering if there is a simple vertical connector to replace a simslot.
This way it would be easier to expand to memory extension cards ( i call these )
Then it would be simple to plug this card in…..
My two cents

Probably!
My liking of this approach is for a couple of reasons though, it's more flexible as what's on the end of the cable could be a breakout board as pictured above or it could just be a RAM card with all the RAM soldered on it (Which I like as angled 72pin sim slots are extreamly hard to source in the UK at any kind of sensible price!) but also because if it works it could potentially work in other macs without any modifications (From what @Trash80toG4 said over on 68kmla it sounds like someone has done a very similar mod to the 475 in the past)

That's not to say it's not a approach I would take, it's just not the one I'm taking currently

So you may be headed toward a hooking up a lot more memory than you think.

I hope so!

 

[Trash80toG4]

I've looked at the only two(?) types of DIMM modules that support DRAM, they utilize FPM DRAM. Chunking their 64bit data path down to two 32bit memory banks would be like installing a pair of 72pin SIMMs. 72/144 and 100/200 packages exist, dunno how many are out there by now and the latter may have only been used by Sun?

Bounced the DIMM thing off @trag a couple of times and got some roadblocks identified. That was years ago, so all is a bit hazy. At least the 5V->3.3V barrier has been breached to a significant extent I think, IIRC that was but one of the problems.

 

[Trash80toG4]

it could just be a RAM card with all the RAM soldered on it (Which I like as angled 72pin sim slots are extreamly hard to source in the UK at any kind of sensible price!)

Connectors are always expensive. I say go SMT with SIMMS by beveling the edge at 45 degrees. It should be easy enough for me to come up with a jig for using the Dremel everyone but me seems to have. One part holds the Dremel at that angle and the second would be a slide setup that mates with the Dremel assembly's slide track.

Bolt the SIMM down to the carrier and zip it past the cutting tool. If there's a 45 degree cone shaped milling bit available all the better?

There's another way to go about hooking up a 72pin SIMM sans connector, but assembly's a massive PITA I think. Adds a bit of flexibility for rework as opposed to the bevel/SMT thing.

 

[max1zzz]

Connectors are always expensive. I say go SMT with SIMMS by beveling the edge at 45 degrees. It should be easy enough for me to come up with a jig for using the Dremel everyone but me seems to have. One part holds the Dremel at that angle and the second would be a slide setup that mates with the Dremel assembly's slide track.

I think if we are going that route I would be tempted to have a slot cut on the board, if it was the right width you should be able to get the correct angle on the simms without having to cut them

Also I got some new 32MB SIMMS today and can confirm for anyone having doubts that 68MB 100% works:

 

[max1zzz]

And the breakout SIMM and triple riser have been sent off to JLCPCB
While i'm waiting for them I'll probably draw up a "direct riser" design too

 

[lilliputian]

Am I understanding correctly, that there'll room for three 32MB modules?

 

[max1zzz]

Am I understanding correctly, that there'll room for three 32MB modules?

Almost, two 32MB's and one 16MB. the top slot only has one RAS line connected to it so will only work with single rank SIMMS which due to the ammount of address lines available is limited to 16MB (32's have two ranks of 16MB each on them)

 

[lilliputian]

Almost, two 32MB's and one 16MB. the top slot only has one RAS line connected to it so will only work with single rank SIMMS which due to the ammount of address lines available is limited to 16MB (32's have two ranks of 16MB each on them)

Gotcha. Thanks for clarifying!

 

[trag]

And the breakout SIMM and triple riser have been sent off to JLCPCB
While i'm waiting for them I'll probably draw up a "direct riser" design too

Been away/busy for several months. There is/was a 64MB composite SIMM by HP, 72 pin, that could be useful. It won't get you to 80, but would be a simple way to provide 64 + 4 and only modify the LCIII to the extent of running the RAS lines.

This HP SIMM has 4 banks of 16 on board but uses some logic to make them look like a single bank of 64.

So the SIMM would need modification to get the RAS lines right. Then it would plug directly into the LCIII SIMM slot. Connect the extra RAS lines and Bob's your uncle.

I'll try to better identify the SIMM later. It's about double height so I'm not sure about mechanics.

May be a while. I'm not really back.

These. Other auctions for same thing available first one I found. Should rcheck my facts. Working off old memories. Haven't examined them in ages.

HP A2580-80001 64MB ECC 60ns 72-Pin SIMM Memory Module for 9000 Workstation | eBay

Find many great new & used options and get the best deals for HP A2580-80001 64MB ECC 60ns 72-Pin SIMM Memory Module for 9000 Workstation at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[max1zzz]

Been away/busy for several months. There is/was a 64MB composite SIMM by HP, 72 pin, that could be useful. It won't get you to 80, but would be a simple way to provide 64 + 4 and only modify the LCIII to the extent of running the RAS lines.

This HP SIMM has 4 banks of 16 on board but uses some logic to make them look like a single bank of 64.

So the SIMM would need modification to get the RAS lines right. Then it would plug directly into the LCIII SIMM slot. Connect the extra RAS lines and Bob's your uncle.

I'll try to better identify the SIMM later. It's about double height so I'm not sure about mechanics.

May be a while. I'm not really back.

These. Other auctions for same thing available first one I found. Should rcheck my facts. Working off old memories. Haven't examined them in ages.

HP A2580-80001 64MB ECC 60ns 72-Pin SIMM Memory Module for 9000 Workstation | eBay

Find many great new & used options and get the best deals for HP A2580-80001 64MB ECC 60ns 72-Pin SIMM Memory Module for 9000 Workstation at the best online prices at eBay! Free shipping for many products!

www.ebay.com

Very interesting,
That seems a very good way to go and is more closer to what I was originally thinking about doing
Those Simms are had to get over here but I can easily get hold of 4mx4 DRAM IC's so could just design a similar simm assuming there is enough space in the LC case

 

[max1zzz]

And a couple of things I have discovered while playing around: The LCIII needs the onboard RAM bank to be present otherwise it produces chimes of death (even with SIMMS in either or both of the other slots) and secondly that onboard bank is limited to 4MB, if you install more it simply doesn't see more than 4MB. This is likely a limitation of the ROMS or maybe of the Sonora it's self

Looks like 68MB will be the limit on the LC III

 

[cy384]

...This is likely a limitation of the ROMS...

yes, the ROM seems to have a hard-coded assumption

afaict it's this snippet

does the LC III have a ROM socket? if so, it might be "easy" to change the behavior here with a custom ROM

 

[Trash80toG4]

Uniserver successfully upgraded LCIII onboard DRAM chips to double the capacity to 8MB in Bank A, that worked just fine. His hack maxed out what the IC Package supported. So I don't think there would be a ROM limitation.

I'll try to search out that thread at the MLA.

edit: found something, maybe not. This was the 605/475 board upgrade.

Q605/LC475 (onboard) ram upgrade.

Ok, so i have some good news… the the Logic Board still boots and runs with out the 4megs of ram soldered onboard. so that is pretty cool. Screen Shot 2013-12-28 at 7.36.17 AM.png[/attachment]

68kmla.org

Thinking it should work in LCIII, but you've already tried 0MB/8MB configurations? Have you tried turning off the memory check at startup?

ROM limitation was for LC and retained for LCII. Removing the 10MB ceiling for the much improved LCIII, wouldn't necessarily mean Apple would limit memory in ROM?

I'll keep looking . . .

 

[max1zzz]

yes, the ROM seems to have a hard-coded assumption

afaict it's this snippet

does the LC III have a ROM socket? if so, it might be "easy" to change the behavior here with a custom ROM

Yep ROM's are socketed

If someone whats to have a go at modifying it that would be really cool, software is not my expertise....

Thinking it should work in LCIII, but you've already tried 0MB/8MB configurations? Have you tried turning off the memory check at startup?

I tried 0/8/16MB, 0MB gives death chimes anything else works but only 4MB is seen