Breaking the 36MB RAM limit on the LCIII

[Trash80toG4]

Not really - some of us migrated entirely away from other forums when TD came into being

Hence, the "have been" caveat, Kai!

I've been having trouble finding much of interest back there in terms of development/tinkering with hardware since the mass migration of talent. Hope you folks don't mind my tagging along, hopefully a side order of crazy added onto the menu for this place is appreciated.

 

[-SE40-]

So, I did endup here….on the darkside,
… the place nobody talks about……

 

[max1zzz]

It works! Just have to hope that simm will still fit in the case

 

[Trash80toG4]

Fabulous, max!

 

[-SE40-]

You did it again!
Congrats

 

[Trash80toG4]

Forgot to ask about the two wires on the layout. Couldn't see if they lead to addressing for a single or multiple Ranks. At first glance I'd thought you were powering that bloody big bodge of ICs, very clever way to implement the jumper wiring. Will you be adding the matched header to your Reloaded LCIII designs? Most elegant that I think.

 

[max1zzz]

Forgot to ask about the two wires on the layout. Couldn't see if they lead to addressing for a single or multiple Ranks. At first glance I'd thought you were powering that bloody big bodge of ICs, very clever way to implement the jumper wiring. Will you be adding the matched header to your Reloaded LCIII designs? Most elegant that I think.

The two extra wires pick up the two additional RAS signals form the bottom of the board, it's essentially just a custom quad rank SIMM

I hadn't thought of adding a header to the reloaded designs, I'll defiantly be doing that now

 

[retr01]

What is your backup plan if this will not fit in the LCIII case, @max1zzz?

 

[max1zzz]

What is your backup plan if this will not fit in the LCIII case, @max1zzz?

Plan....... um yes, I deffinatly have one of those!

The good news is a plan is not needed, the SIMM fits just fine with some room to spare

 

[Trash80toG4]

The two extra wires pick up the two additional RAS signals form the bottom of the board, it's essentially just a custom quad rank SIMM

Thanks, should have figured out it was RAS from the way they run across the ICs as if P&G to the corners of the chips. Brain's only partially online lately, trying to shake off Wuhan Wooziness.

I hadn't thought of adding a header to the reloaded designs, I'll defiantly be doing that now

Cool, at least some of my noggin's still up and running.

 

[retr01]

Plan....... um yes, I deffinatly have one of those!

The good news is a plan is not needed, the SIMM fits just fine with some room to spare

HIGH FIVE @max1zzz! You nailed it!

Have you run tests via Apple Personal Diagnostics, MacTest, etc., for 4+ hours to ensure it can handle the rigor of whatever?

 

[Trash80toG4]

How goes it on this one? Is your board ready for prime time?

Haven't seen an update on any of your projects for a bit?

 

[retr01]

Yeah, I am with @Trash80toG4. I am wondering the same thing. The LC III is a nice Mac. Can it go to 128 MB like the SE/30?

 

[ClassicHasClass]

I also wrote a few tomes on the architecture of the X500 PCI Macs. That's probably gone forever.

Didn't happen to have anything on the 6500, did you? I'm puzzling through why the BeOS AWACS driver works on the 6400 but not the 6500/TAM.

 

[max1zzz]

How goes it on this one? Is your board ready for prime time?

Haven't seen an update on any of your projects for a bit?

Yeah, I am with @Trash80toG4. I am wondering the same thing. The LC III is a nice Mac. Can it go to 128 MB like the SE/30?

Well the boards work, I was going to assemble and sell a couple but my cheap source of DRAM IC's fell through and the next cheapest source is about £1 a chip so with 32 chips and assembly I would probably have to sell tham at £60-£70 each which I suspect is more than anyone would pay....

Really need to get around to uploading the board design to github (Along with tha IIcx and Plus boards...)

The LCIII can't go to 128Mb sadly as it lacks the 12th address line needed to get bigger SIMMS to work.

 

[retr01]

The LCIII can't go to 128Mb sadly as it lacks the 12th address line needed to get bigger SIMMS to work.

Tangent to this thread on LC III memory expansion, for the 040 based such as LC475, P475, P476, Q605, etc., MicroMac did make a memory that breaks the 36 MB barrier. See this link:

MicroMac 64MB and 128MB BigSIMM Memory Upgrade SIMM for Macintosh

The MicroMac 64MB or 128MB BigSIMM memory upgrade product increases the memory capacity of certain Macintosh LC, Macintosh Performa, Macintosh Quadra and PowerMac models beyond the traditional memory limit to 68MB, 132MB or even more

www.micromac.com

Is this something that can be looked into (or discussed) in another thread?

 

[max1zzz]

Tangent to this thread on LC III memory expansion, for the 040 based such as LC475, P475, P476 Q605, etc., MicroMac did make memory that breaks the 36 MB barrier. See this link:

MicroMac 64MB and 128MB BigSIMM Memory Upgrade SIMM for Macintosh

The MicroMac 64MB or 128MB BigSIMM memory upgrade product increases the memory capacity of certain Macintosh LC, Macintosh Performa, Macintosh Quadra and PowerMac models beyond the traditional memory limit to 68MB, 132MB or even more

www.micromac.com

Is this something that can be looked into (or discussed) in another thread?

Would be very intresting to see one of those SIMMS and try to figure out what it's doing, I haven't ever seen one for sale though

 

[retr01]

Would be very intresting to see one of those SIMMS and try to figure out what it's doing, I haven't ever seen one for sale though

You're right. Those come up rarely, if ever. I suspect it was not sold well back in the day due to its high cost versus standard memory, which was more affordable than the "BigSIMM" by MicroMac.

Maybe someone here or on 68kmla will have one?

Actually, 64 MB and 128 MB were later possible as memory prices went down. 64 MB and 128 MB SIMMs were installed in various 040 Macs. Many of those 040 Macs have the same boards for specific series. I doubt anything special about the MicroMac BigSIMM as it was a DRAM SIMM. The only issues were single or double banked and other physical constraints of those SIMMs which various discussion can be found elsewhere online.

If anyone knows otherwise, feel free to PM me. Okay, back on topic!

 

[Trash80toG4]

General maximum memory config info:
It wasn't just memory pricing, release dates of higher DRAM capacity/SIMMs plays a big part as well. Apple's maximum supported memory configs are based on SIMM capacities available and tested at time of release. Models were already obsolescent when higher capacity SIMMs/DIMMs hit the market . . . or Apple Marketing wanted to lead customers to believe so.

 

[retr01]

General maximum memory config info:
It wasn't just memory pricing, release dates of higher DRAM capacity/SIMMs plays a big part as well. Apple's maximum supported memory configs are based on SIMM capacities available and tested at time of release. Models were already obsolescent when higher capacity SIMMs/DIMMs hit the market . . . or Apple Marketing wanted to lead customers to believe so.

Yeah, I agree with those factors. And, I think that Apple did use the words "maximum RAM" in their materials, told all that to the dealers, etc. Many people believed in one big lie about the Q605, LC475, P475, P476, and other newer LC models, such as the 575, that could support more than 36 MB of RAM. Of course, people didn't see this as a lie, just simply the "fact" of the time.

However, I do perceive Apple lying to dealers and customers as a huge problem back in the day, and many people blindly believed and trusted Apple.