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Very neat potential solution for our 30-pin Macs and wanting ALL THE MEMORY

Bolle

Well-known member
I would like to see somebody make some PAL 30 pin SIMMs (4 or 16MB) so I can use them on my Mac II/IIx machines.
I am on it, it’s just at the very end of the to-do list and other stuff seems to crop up ahead of it everytime something else actually gets done.

This reminds me, I was going to look into modifying the II logicboard to accept standard RAM as well... I made up a mod in the sketchbook which would be completely reversible but didn’t actually try it yet.

 

Elfen

Well-known member
I made one that uses two 16M*4 chips. I used to source those chips from 128MB 72pin modules. One 72pin SIMM will give you enough chips to build 8 30pin SIMMs this way.

If you go for parity 72pinners you will even get some spare 16M*1 chips which will usually fit onto the IIfx SIMM design that's floating around.

View attachment 38420


Never a LIKE Button to press when you need one!

 

MrFahrenheit

Well-known member
This topic makes me wonder about something else, but similar.

The Macintosh LC has solder pads on the motherboard for RAM, and Apple only populated one half of the pads.  I wonder if anyone has (or if it would even work) soldered on same size RAM modules onto the other pads to have 4MB soldered onto an LC board, instead of just 2.

 

jessenator

Well-known member
This topic makes me wonder about something else, but similar.


A former user did something similar with the IIsi: they took faster, higher density RAM off a dead 6100 board and replaced the IIsi on-board RAM. I think they also did something similar with a Classic board, now that I'm looking for it and failing to source the 6100-IIsi thread.

You have plenty of LCs though ;)  let us know what the results are!

 
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max1zzz

Well-known member
This topic makes me wonder about something else, but similar.

The Macintosh LC has solder pads on the motherboard for RAM, and Apple only populated one half of the pads.  I wonder if anyone has (or if it would even work) soldered on same size RAM modules onto the other pads to have 4MB soldered onto an LC board, instead of just 2.
I tried it before, it didn't work (You get chimes of death iirc)

I never did any testing besides soldering the chips on and flicking the power switch so I'm not saying it's totally impossible, but it's not just as simple as dropping some extra chips on to the board

 

max1zzz

Well-known member
for some reason I can't edit my last post....

Anyway, dug up my old thread where I tried it the LC was just not seeing the RAM, it wasn't giving chimes of death

Looking at the schematic for the LC II there are 22ohm resistiors on the CAS lines for the RAM IC's that would be missing on the LC 1. I'm betting those aren't populated on the LC 1 and finding and populating them would get the extra RAM seen

 

Torbar

Well-known member
In Adrian's latest mailcall video, someone sent him a solder stencil.  So I'm sure some kind of follow up video where he does a more proper technique will be released soonish

 

trag

Well-known member
I made one that uses two 16M*4 chips. I used to source those chips from 128MB 72pin modules. One 72pin SIMM will give you enough chips to build 8 30pin SIMMs this way.


Do those 2-chip 16MB SIMMs work in the SE/30?  Do you know?   I laid out a board for a 2 chip 30 pin SIMM back when I was doing IIfx SIMMs, but never made any.  PCB prices at the time were still prohibitive.  Seed Studio and others had not yet emerged.  I only made the IIfx SIMMs because one of the fabs sent me a $500-off coupon.

 

olePigeon

Well-known member
I used a single, unrefrigerated tube of solder paste for years.  Yes, it got thick and goopy, but it was perfect for surface mount capacitors.  Two dabs of sticky stuff, plop the cap on it (it doesn't move cuz it's so sticky), then just touch the solder tip to the goop and watch it melt.  Good stuff.

 

Bolle

Well-known member
Do those 2-chip 16MB SIMMs work in the SE/30?  Do you know?


So far I have been using them in the SE/30, IIci and Q950 without any major problems.

The only issue I have is with the thickness of the SIMMs. As with the ROM SIMMs 1.2mm seems to be slightly too thin and 1.6mm is pretty tough to get into some sockets.

Just like with ROM SIMMs 1.4mm would probably be perfect here.

 

trag

Well-known member
So far I have been using them in the SE/30, IIci and Q950 without any major problems.

The only issue I have is with the thickness of the SIMMs. As with the ROM SIMMs 1.2mm seems to be slightly too thin and 1.6mm is pretty tough to get into some sockets.

Just like with ROM SIMMs 1.4mm would probably be perfect here.


Thank you, Bolle.  I thought I had read something, maybe in an Apple Tech note, about 2-chip SIMMs not being supported in the SE/30 (and others) because of some difference in refresh in X4 chips.   But either I misremembered, or it was another one of those cautions that doesn't seem to apply in actual practice.

Yes, in theory, you really want 1.27 mm. or .050", but it seems difficult to find.   Ten years ago it was, not exactly common, but readily available.

 

max1zzz

Well-known member
So far I have been using them in the SE/30, IIci and Q950 without any major problems.

The only issue I have is with the thickness of the SIMMs. As with the ROM SIMMs 1.2mm seems to be slightly too thin and 1.6mm is pretty tough to get into some sockets.

Just like with ROM SIMMs 1.4mm would probably be perfect here.
Which size did you end up using? I have had issues with the 1.2mm PCB's, wondering if 1.6mm is the way to go or if it is better sticking with 1.2mm and bodgeing something together when they are too loose in the slot

 

Bolle

Well-known member
I actually ended up soldering most of the modules down on boards that would have needed new SIMM sockets anyways.

1.6mm really is too thick, you will get them into the sockets but once you take them out again the socket won’t reliably hold any standard SIMMs anymore with good contact.

 
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Chopsticks

Well-known member
Do those 2-chip 16MB SIMMs work in the SE/30?  Do you know?   I laid out a board for a 2 chip 30 pin SIMM back when I was doing IIfx SIMMs, but never made any.  PCB prices at the time were still prohibitive.  Seed Studio and others had not yet emerged.  I only made the IIfx SIMMs because one of the fabs sent me a $500-off coupon.
i just had some of Bolle's 2-chip sims manufactured at 1.2mm thickness, i applied 3-4 layers of kapton tape to the back side near the contacts for the sockets and they work fine, my se/30 shows the full 128mb, i think the exact spec of thickness required is about 1.37mm, but using the tape has been reliable for me over the last week or so in daily use

 

jessenator

Well-known member
i think the exact spec of thickness required is about 1.37mm
I'd like to know just so I can put my mind at ease (as I don't engineer/build myself, this is just a fact my brain wants to know :p ), because after seeing several of these and a few other posts about this and how it's plaguing new builds for our old machines.

I went ahead and measured a few sticks of my of-the-time 30-pin RAM and my OEM SE/30 ROM SIMM I have and they're all 1.20–1.25 mm by my caliper measurement (margin of error is usually ±0.01 mm on mine). So I don't know if I'm measuring wrong (don't know how I could with the board thickness…) or if I have mutant sockets, or what the deal is. ¯\_(ツ)_/¯

 
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Chopsticks

Well-known member
I'd like to know just so I can put my mind at ease (as I don't engineer/build myself, this is just a fact my brain wants to know :p ), because after seeing several of these and a few other posts about this and how it's plaguing new builds for our old machines.

I went ahead and measured a few sticks of my of-the-time 30-pin RAM and my OEM SE/30 ROM SIMM I have and they're all 1.20–1.25 mm by my caliper measurement (margin of error is usually ±0.01 mm on mine). So I don't know if I'm measuring wrong (don't know how I could with the board thickness…) or if I have mutant sockets, or what the deal is. ¯\_(ツ)_/¯
well i can 100% confirm bolle's 2 chip simms he posted here work fine. i had some issues with the sim socket connections that was fixed by adding some caption tape to the back side of the sim pcbs i used 3 or layers myself but you may only need 1-2 yourself.

i also had to add 2 layers of kapton tape to my 8mg ROM Simm but i did replace the socket awhile ago with a better quality one so you may have different results there.

if you're worried about it working, honestly dont as they will either work fine or just need some tape to thicken them up a little...

im pretty sure the original simm spec was done in mills, not mm, but the conversion is about 1.37mm

 
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jessenator

Well-known member
but you may only need 1-2 yourself.
Sorry. What I meant to say is the 30-pin RAM and the ROM that was original in my Macs has that measurement. I actually don't currently own any reproduction memory modules, just a MacSIMM ROM which is currently in my SE/30—and , in full transparency, I'm not trying to be belligerent or argumentative at all! I just want to know what the heck is going on :lol:

Just took my SE/30 ROM and measured across the contact portion the PCB again: 1.25mm which is about 49 mils when I switch to decimal inches, 3/64 in fractional inches. Across the bare board it's around 46–47 mils or 1.20 mm. SO …IDK :lol: I even pulled out the feeler gauges I have for automotive work, and matched all of them on the mils side with the same calipers: .008, .010, .012, .014

 

Chopsticks

Well-known member
Sorry. What I meant to say is the 30-pin RAM and the ROM that was original in my Macs has that measurement. I actually don't currently own any reproduction memory modules, just a MacSIMM ROM which is currently in my SE/30—and , in full transparency, I'm not trying to be belligerent or argumentative at all! I just want to know what the heck is going on :lol:

Just took my SE/30 ROM and measured across the contact portion the PCB again: 1.25mm which is about 49 mils when I switch to decimal inches, 3/64 in fractional inches. Across the bare board it's around 46–47 mils or 1.20 mm. SO …IDK :lol: I even pulled out the feeler gauges I have for automotive work, and matched all of them on the mils side with the same calipers: .008, .010, .012, .014
nah i didn't find you argumentative or anything so no dramas there  :)

yeah im not to sure like I have some Mac rom Simms that are 1.38mm and 1.40mm so I honesty don't know what the situation is there? maybe some of the Mac roms came from different suppliers with different tolerances in their pcbs fab houses?

im from Australia myself so if its not in metric measurements I have no clue lol

I was mainly just trying to let you know that Bolle's ram sims work great and not to worry about if they would work or not as you can shim them with some tape etc

ive had many ram Simms in my se/30 during a bunch of testing over the years so there's a good chance that my Simm sockets are a bit 'tired' as needing 3-4 layers of kapton tape is a couple layers more then I'd have thought it would need

 
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