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Wombat (650, 800) board overclocking limitations

Jockelill

Well-known member
This is in production now in China :), will arrive next week, then I need to run some testing and send out a few beta units.

The simm will automatically switch some pins between se/30 and “Quadra”. It’s 4MB because this is the maximum you can use with the apple flasher tool (as per @dougg3 findings). So this ROM simm will work in anything from a SE/30 to Quadra 840AV. Of course with different images! It’s also compatible with @dougg3 s programmer and all derivatives (@WillJac and @bigmessowires ).

The idea that this SIMM can be used in conjunction with a hacked flasher tool that @dougg3 is working on :).

As for ROM hacking, that’s for whole other thread 🧵 😄
 

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eharmon

Well-known member
This is in production now in China :), will arrive next week, then I need to run some testing and send out a few beta units.

The simm will automatically switch some pins between se/30 and “Quadra”. It’s 4MB because this is the maximum you can use with the apple flasher tool (as per @dougg3 findings). So this ROM simm will work in anything from a SE/30 to Quadra 840AV. Of course with different images! It’s also compatible with @dougg3 s programmer and all derivatives (@WillJac and @bigmessowires ).

The idea that this SIMM can be used in conjunction with a hacked flasher tool that @dougg3 is working on :).

As for ROM hacking, that’s for whole other thread 🧵 😄
That needs an 822033-2 or a PE HWS1788-equivalent socket, right? Getting my socket order in now 😛
 

eharmon

Well-known member
So it does fully configure as a Q800. Very strange! I wonder if the 475 ROM can no longer differentiate between Wombat configurations!
 

eharmon

Well-known member
I was pretty surprised it booted at all with the 475 ROM :).
Now that I think about it, the 475 and Q650 basically came out the same day.

While the 475 ROM has a later date and higher version (4.0 v. 4.1), I wonder if it branched before Q650 detection was implemented, so the system defaults to Q800...
 

zigzagjoe

Well-known member
Bought a loose Centris 650 board as my first quadra for troubleshooting purposes. 25mhz originally, board came with a 70mhz PLL, 8MB of 80ns RAM, E31F 68040HRC25 CPU.

No issues putting a 20mhz crystal on it with the gestalt 36 resistors. I removed the original crystal and bent the legs of a half-size can as it was easier than leaving the original in place (also, it was what was in my junk box). Stuck a 40mm fan on the CPU to be safe as this board has no case to live in, though the CPU seems to run cooler than the E31F @ 45mhz in my SE/30.

Nothing really surprising here, but figured I'd put the data out there.

1701579469906.jpeg
 

eharmon

Well-known member
Bought a loose Centris 650 board as my first quadra for troubleshooting purposes. 25mhz originally, board came with a 70mhz PLL, 8MB of 80ns RAM, E31F 68040HRC25 CPU.

No issues putting a 20mhz crystal on it with the gestalt 36 resistors. I removed the original crystal and bent the legs of a half-size can as it was easier than leaving the original in place (also, it was what was in my junk box). Stuck a 40mm fan on the CPU to be safe as this board has no case to live in, though the CPU seems to run cooler than the E31F @ 45mhz in my SE/30.

Nothing really surprising here, but figured I'd put the data out there.

View attachment 66114
Huh, didn’t know Apple sold machines with HRC versions. That’s interesting in itself.
 

zigzagjoe

Well-known member
Huh, didn’t know Apple sold machines with HRC versions. That’s interesting in itself.
First I'd seen it mentioned also. There was no thermal interface material beneath the heatsink, but that could be normal. The rest of the board gave no signs of being monkeyed with, given it had wet dust "mud" all over the board and the original Saft battery.

Has anyone come up with an official (motorola) definition of what HRC is, anyways? I've only heard apocryphal statements that it's a low-heat version.
 

eharmon

Well-known member
First I'd seen it mentioned also. There was no thermal interface material beneath the heatsink, but that could be normal. The rest of the board gave no signs of being monkeyed with, given it had wet dust "mud" all over the board and the original Saft battery.

Has anyone come up with an official (motorola) definition of what HRC is, anyways? I've only heard apocryphal statements that it's a low-heat version.
There's normally paste between a square block heatsink (older Quadras) or the 45 degree mounted crown-style heatsink (newer Quadras). So maybe it is a swap.

I searched high and low and I've yet to see documentation from Motorola on what an HRC is. But the claims are pretty universal that it's low heat. Given the 25MHz should run ice cold on a E31F, I kinda wonder if it's just a marketing exercise to match certain customer's needs. An HRC D50D would be much more surprising.
 

eharmon

Well-known member
Once you're using the 40MHz timings, the bottleneck perhaps will be the MC88920 (what speed rating are yours?).
Circling back to this, cause I forgot, doesn't the Wombat run an MC8816DW? Am I forgetting about another clock doubler on the board?

The Q800 board has a 55MHz, the Q650 has a 70MHz...which might also explain why it overclocks a bit higher. Alas...but...weird? Did some Q800 ship with the chip overclocked? The C650 also has a 55MHz, but that makes more sense. However, my 55MHz parts are XC and the 70MHz is an MC, so maybe Moto just qualified it for faster speeds later without really changing the mask so the earlier parts are good for 70.

Realistically, the Q800 posts at fast speeds, it just seems to struggle with timings (OS gets stuck while booting -- mouse keeps moving though). Which makes me doubt the 8816DW itself is causing problems.
 

Phipli

Well-known member
Circling back to this, cause I forgot, doesn't the Wombat run an MC8816DW? Am I forgetting about another clock doubler on the board?
Sorry, my bad, they're interchangeable and have the same pinout, I got the part numbers backwards.

The 475 has a 88920 and I swapped in an 88916 - they're all similar parts.
The Q800 board has a 55MHz, the Q650 has a 70MHz...which might also explain why it overclocks a bit higher. Alas...but...weird? Did some Q800 ship with the chip overclocked? The C650 also has a 55MHz, but that makes more sense. However, my 55MHz parts are XC and the 70MHz is an MC, so maybe Moto just qualified it for faster speeds later without really changing the mask so the earlier parts are good for 70.
Wait, what?? Your Q800 has a 55? That's unexpected. Are you sure that isn't a board from a C650?
Realistically, the Q800 posts at fast speeds, it just seems to struggle with timings (OS gets stuck while booting -- mouse keeps moving though). Which makes me doubt the 8816DW itself is causing problems.
Yes, but I said :
Once you're using the 40MHz timings, the bottleneck perhaps will be the MC88920 (what speed rating are yours?).
I didn't see you say you had tried the 40MHz timings yet? I meant in terms of pushing to 50MHz and beyond.

This assumes you have a fast enough CPU too sorry.
 
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eharmon

Well-known member
Sorry, my bad, they're interchangeable and have the same pinout, I got the part numbers backwards.

The 475 has a 88920 and I swapped in an 88916 - they're all similar parts.

Wait, what?? Your Q800 has a 55? That's unexpected. Are you sure that isn't a board from a C650?

Yes, but I said :

I didn't see you say you had tried the 40MHz timings yet? I meant in terms of pushing to 50MHz and beyond.

This assumes you have a fast enough CPU too sorry.
No, still waiting on the new ROM boards to try new timings.

I'm pretty dang sure it's a Q800. The LED connector and second speaker connection are both factory.
 

Phipli

Well-known member
No, still waiting on the new ROM boards to try new timings.

I'm pretty dang sure it's a Q800. The LED connector and second speaker connection are both factory.
You don't need anything other than the stock ROM to try 40MHz timings?
 

eharmon

Well-known member
You don't need anything other than the stock ROM to try 40MHz timings?
Oh, right. Pull the resistors to change the board ID. I was just gonna wait and munge in a ROM socket cause it's more flexible.

Here's the 55 btw, plain as day:
1701641307936.png
 

Phipli

Well-known member
Oh, right. Pull the resistors to change the board ID. I was just gonna wait and munge in a ROM socket cause it's more flexible.

Here's the 55 btw, plain as day:
View attachment 66152
There is an unpopulated resistor in the board ID circuit that leads to an unpopulated jumper position. If you fit the resistor and the 2 pin jumper, placing a jumper and removing it is all that is needed to do to switch between 33MHz and 40MHz timings, that's how I have my board set up.

Required bits - 1 resistor, 1 header, 1 jumper.

Process to switch timings - shutdown, fit or remove jumper, boot.

I spent... way too long playing with my Centris 650 and Quadra 610. I got my Quadra 610 to boot at 48MHz, but it crashed before I could finish a benchmark.
 

Phipli

Well-known member
1701642456108.png

asdf
1701642537325.png

You can use the jumper to either select 20 vs 25MHz, or 33 vs 40MHz, depending on if you populate R151 or not, as per the picture above.

Make sure R152 is stuffed with a 1500R resistor (as in the picture) and R233 has something like a 330R resistor (as above).

The pins highlighted between R233 and R148 are the pins for the header.
 
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Phipli

Well-known member
And yes, I fitted a 330 and wrote 300. I didn't have a 300 ohm resistor, but was planning to use one. 330 was what I used instead.
 
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