Power Macintosh 475

[Kai Robinson]

The mythical beast that is the PPC601 Upgrade card, and the LC475, smashed together!

This started life as a Japanese LC475 (no different to any other 475, but it's from Japan and therefore, cooler than yours). It actually came already with a 32MB SIMM in it and 2 x 512kb VRAM SIMM's, but no hard disk. So i stuck a SCSI2SD in it and got System 7.5.3 installed on it.

Then, the Apple PPC Upgrade card arrived in the mail.. 4 Months after I won the auction for it!

It initially looked damaged in transit, so i got a few (90), PPC601 chips to repair it, only for it to actually work just fine. It even has the optional 256kb L2 Cache module installed. And of course, I put in a full fat 68040 and heatsink for good measure.

The only issue is the 25MHz bus means the PPC Upgrade card runs at just 50MHz, which is far too slow. The CPU on the card, is actually rated for 75MHz or 100MHz respectively. So i did the 33MHz bus overclock for the 475 and lo-and behold, the PPC accelerator was just fine with that, bumping up to 66MHz.

Still have no idea what to really do with it other than load up SimCity 2000 on it

 

[MacKilRoy]

Very nice! Totes jelly

 

[Kai Robinson]

Very nice! Totes jelly

I'm jelly of myself with this one - it's like the holy grail of rare-ass accelerators...and I GOT ONE!

I am never, ever parting with this machine...

 

[Mark Fixes Stuff]

This upgrade would be better if it was in my house.

 

[Kai Robinson]

This upgrade would be better if it was in my house.

I do have a spare LC475 you can use...

 

[LeadedSolder]

Time to benchmark drag race it against a 6100. Fantastic work. Does it get hot?

 

[Fizzbinn]

View attachment 1971The mythical beast that is the PPC601 Upgrade card, and the LC475, smashed together!

This started life as a Japanese LC475 (no different to any other 475, but it's from Japan and therefore, cooler than yours). It actually came already with a 32MB SIMM in it and 2 x 512kb VRAM SIMM's, but no hard disk. So i stuck a SCSI2SD in it and got System 7.5.3 installed on it.

Then, the Apple PPC Upgrade card arrived in the mail.. 4 Months after I won the auction for it!

It initially looked damaged in transit, so i got a few (90), PPC601 chips to repair it, only for it to actually work just fine. It even has the optional 256kb L2 Cache module installed. And of course, I put in a full fat 68040 and heatsink for good measure.

View attachment 1972
The only issue is the 25MHz bus means the PPC Upgrade card runs at just 50MHz, which is far too slow. The CPU on the card, is actually rated for 75MHz or 100MHz respectively. So i did the 33MHz bus overclock for the 475 and lo-and behold, the PPC accelerator was just fine with that, bumping up to 66MHz.

View attachment 1973

Still have no idea what to really do with it other than load up SimCity 2000 on it

Awesome! I hope to join you in this one day, with a Power Macintosh 605/100 in my case! This is one of the many project that I have on deck held up by something or another. My problem here is while I have the DayStar 100MHz version (yay!) and it lets you set the bus clock multiplier to 3x or 4x with a jumper…

…it is missing some pins on the 68040 socket connector (BOO!)

There has to be some way to repair this… My first thought is a tiny drill bit into the missing pin stubs and soldering in replacement pins but that is likely much harder than it sounds and it sounds hard to me!

Any ideas? Thoughts? Advice?

 

[Fizzbinn]

I also wonder if the Apple version can actually do 3x or 4x bus multipliers if some resistors are moved around. I‘m pretty sure I read somewhere that DayStar built the Apple one for them so the two boards are likely very similar...

 

[jajan547]

I've been looking for one of these for months, I want one badly lol.

 

[Kai Robinson]

I also wonder if the Apple version can actually do 3x or 4x bus multipliers if some resistors are moved around. I‘m pretty sure I read somewhere that DayStar built the Apple one for them so the two boards are likely very similar...

I too would be very interested to learn the difference. The main ASIC is identical, it's just the Clock/PLL circuitry that there may be differences - perhaps we could each take some images of the boards to see what these differences might be?

 

[Jagmn]

Sorry to resurrect this thread. I have just acquired and 'repaired' a 475 that had the Apple 601 upgrade card installed and was interested to know if any comparisons to the Daystar + Clock/PLL circuitry have been made?

 

[trag]

On the Turbo601 for the 68030 Macs, the difference between the 66MHz version and the 100 (99) MHz versions was the addition of an ICS9178 clock buffer/PLL chip. As far as I can tell, this chip handled converting the 33MHz bus signal to 3X for the PPC601 -- apparently it does not have internal multipliers like later PPC chips.

However, I don't see any pads on the Apple upgrade that would support an ICS9178 or really any additional clock buffering/multiplying chip.

I speculate that the 66MHz version didn't need a special chip to get 2X because that's easy with common logic, but 3X requires more finesse.

I sold my Turbo601 long ago, so I no longer have one to examine. It was a bit of a dancing bear. The wonder was not that it danced well, but that it danced at all.

https://www.highox.com/dt601.html

Please excuse the rather primitive soldering advice in the article. That was like 25+ years ago...

 

[Jagmn]

Thanks Traq, that's some good illumination. I was planning on overclocking a 475 and 575 anyway, so that seems like a simpler solution than trying to work a new chip into the mix. I'd still be interested if anyone has pictures of the later Daystar 68040/601 version of this card I've snagged.

 

[Kai Robinson]

Easier to pump the bus speed from 25MHz to 33MHz, you'll gain 16MHz on the PPC side of things without you even touching the card.