MicroMac MultiSpeed speed upgrade?

[ObeyDaleks]

Hi. Does anybody know if the 16Mhz MicroMac MultiSpeed accelerator can be upgraded to a faster version?

Looks like they came in 16, 25, and 32Mhz versions.

Does anybody know if it would be just a straight crystal/CPU swap? Or is there more to it than that? I assume the 25Mhz version is just an overclock, and the 32Mhz is a faster CPU and crystal?

 

[Nixontheknight]

I'd say any upgrade of the speed would be a CPU swap because each CPU has its speed rating on it, but you can always underclock the highest clock rating without any problems, as the slower rated CPUs will get warmer than usual at higher speeds

 

[KennyPowers]

My MicroMac MultiSpeed has a 50Mhz crystal. I assume that means it's the 25Mhz model?

 

[ObeyDaleks]

Right, so you have a 50Mhz crystal and 25Mhz processor (I assume). The 16Mhz version has a 33Mhz crystal. So presumably replacing the crystal with 64-66mhz and the processor with a 32Mhz would make this the faster version.

What I’m not sure of, are there other components that would need replacing? I don’t want to fry the board, but the idea of a 32Mhz 68030 Mac SE is enticing.

 

[KennyPowers]

There are 4 jumpers on mine too, but I don't know what they're for. Every picture I've ever seen of a MultiSpeed (with and without FPU) had JP2 closed and JP0, JP1, and JP3 open. I've also seen a few photos with those jumpers hardwired in that configuration. I've seen a photo of one with a 40Mhz crystal too, even though MicroMac's site only advertises 16Mhz, 25Mhz, and 32Mhz versions. Apparently MicroMac also sold a processor clip type thing to use the MultiSpeed in a Plus or Classic. I uploaded a dump of the v3.1 ROM from this accelerator to the garden: https://macintoshgarden.org/apps/micromac-multispeed-accelerator-rom-dump-v31

 

[avadondragon]

@KennyPowers @ObeyDaleks - You should both take some hi-res pics of your boards and compare.

 

[KennyPowers]

@KennyPowers @ObeyDaleks - You should both take some hi-res pics of your boards and compare.

I have a whole thread over on TD where I stumble through recapping and repairing my MultiSpeed...there are plenty of pictures there. There's also a decent-sized picture of the top side of mine in the garden link I posted above

 

[Phipli]

Some of my cards have a divider that can be set with dip switches. The clock can be divided by 2 or 4, independently both before and after the extension loads. With a 40MHz clock you could have it set to start at 10MHz and then switch to 20MHz, or start at 20 and switch to 40MHz, or whatever other combination.

If I was you, I'd find photos of all the variants and work out what the switches do. Then if I had a 16mhz version with a 33mhz clock, I'd put in a 33MHz chip and turn off the divide by two.

 

[Paralel]

Right, so you have a 50Mhz crystal and 25Mhz processor (I assume). The 16Mhz version has a 33Mhz crystal. So presumably replacing the crystal with 64-66mhz and the processor with a 32Mhz would make this the faster version.

What I’m not sure of, are there other components that would need replacing? I don’t want to fry the board, but the idea of a 32Mhz 68030 Mac SE is enticing.

I think you'd use a 33 MHz 68030, the system probably just rounds down with a slower crystal, a very small underclock. 32 MHz is interesting. It might do that because some incompatibilities show up once the full 33 is used.

 

[Phipli]

There were 25MHz grade 030s.



Edit, oh right you are talking about underclocking to 32? That was common enough, but so were 16.666666666MHz clocks speeds and 33.333333Mhz.

 

[Paralel]

There were 25MHz grade 030s.
View attachment 53337

Were the parts ever qualified or did they stay as XC's?

 

[Phipli]

Were the parts ever qualified or did they stay as XC's?

They were qualified later.

There were actual 20MHz rated parts, and 16MHz parts. There were loads of speed grades.

 

[KennyPowers]

Were the parts ever qualified or did they stay as XC's?

CliffsNotes version for those of us that don't know what that means? I mean, I know what it means to qualify a part at certain frequencies, but am unfamiliar with how that corresponds to the markings on these CPUs. The top line on the 030 in my MultiSpeed says "XC68030RC20B". Does that say anything about its supported frequencies?

 

[Phipli]

CliffsNotes version for those of us that don't know what that means? I mean, I know what it means to qualify a part at certain frequencies, but am unfamiliar with how that corresponds to the markings on these CPUs. The top line on the 030 in my MultiSpeed says "XC68030RC20B". Does that say anything about its supported frequencies?

I might get the terminology wrong, but basically, from Motorola, engineering samples start with PC, then full production parts start with XC, until all the bugs are ironed out and when they are, the part is 'qualified' and they switch to MC. I think they are sort of saying there won't be any more functional changes.

PR68040RC25, XC68040RC25 and MC68040RC25, for example.

It lagged so much that Apple moved on before the 040s were ever qualified, so no mac came with an MC68040.

 

[avadondragon]

I mean, I know what it means to qualify a part at certain frequencies, but am unfamiliar with how that corresponds to the markings on these CPUs. The top line on the 030 in my MultiSpeed says "XC68030RC20B". Does that say anything about its supported frequencies?

The number right after the RC is the speed in MHz so that part is rated for 20MHz. Interesting that they clocked it at 25MHz.

 

[Phipli]

The number right after the RC is the speed in MHz so that part is rated for 20MHz. Interesting that they clocked it at 25MHz.

I thought his was a 16MHz board? 20MHz would be over spec slightly.

 

[KennyPowers]

I thought his was a 16MHz board? 20MHz would be over spec slightly.

OP has a 16Mhz board. I think I have a 25Mhz board because the crystal on mine is 50Mhz.

I have an unused-in-box MicroMac DOCI50-FPU that apparently has a 50Mhz 030 on it that I'm not currently using since my IIci has an 040. If the jumpers on this MultiSpeed control the frequency multiplier, I wonder if I could set it to 1:1 and swap in the 50Mhz 030 to have a 50Mhz SE? Not sure I wanna "break the seal" on the DiiMO though. Also, I suppose there could be other components on the MultiSpeed that might not like being clocked that fast?

 

[Phipli]

OP has a 16Mhz board. I think I have a 25Mhz board because the crystal on mine is 50Mhz.

Ah, sorry, I thought the 16MHz board was being discussed. A little cheeky, but a 20MHz chip will run fine at 25MHz usually.

Perhaps someone swapped the clock on a slower board?

 

[ObeyDaleks]

OP has a 16Mhz board. I think I have a 25Mhz board because the crystal on mine is 50Mhz.

I have an unused-in-box MicroMac DOCI50-FPU that apparently has a 50Mhz 030 on it that I'm not currently using since my IIci has an 040. If the jumpers on this MultiSpeed control the frequency multiplier, I wonder if I could set it to 1:1 and swap in the 50Mhz 030 to have a 50Mhz SE? Not sure I wanna "break the seal" on the DiiMO though. Also, I suppose there could be other components on the MultiSpeed that might not like being clocked that fast?

Yeah this is what the only thing I’m afraid of. The processors and crystals are easy and inexpensive to source, so I would be willing to try it as long as I didn’t fry the board in the process. And if the dip switches actually control the multiplier, that would mean it’s a completely solderless installation too. I was hoping someone has already tried it and would give me a yay/nay on this.

But I really want an SE that’s 2-3 times faster than a stock SE/30!

 

[Trash80toHP_Mini]

Interesting board, strange connectors. What machine is it for, a PowerBook?
- has anyone identified a crystal on that board, I didn't see one right off?
- if no crystal's on board, then it's running on a system bus multiplier, which could be problematic.

Long term quest has been running the 68030/16Mhz Performer from my Drexel Plus at 32MHz. But such appears not to be feasible.

@Bolle has cloned it and tried hooking the 8MHz bus clock-doubling GAL to the 16MHz clock on the board. I'd hoped for success there for a very long time™, but timings appear to be too tight for it to work.

Markings appear to indicate 25MHz is a possibility, wondering about timing complications this case?