Forums | MacLife

Yes.
I'll direct you to my old topic ( shameless plug )

Now, unless you're also going to overclock your AGP's bus, which is only reliable in rare instances, you'll want to upclock the processor from the Quicksilver.
You see, it's made to run on a 133mhz bus, and will therefore run more slowly than rated on your AGP Sawtooth's 100mhz bus, and by a large margin, at that ( an 867mhz in a QS will only run at 650mhz in a Sawtooth ).

You'll also need to add 12volts to the QS card for it to operate in your machine. I spliced a yellow hard drive power cable.

If you read through my topic and peek at the photos, it's all in there.

Hope that helps.

Ironhawk: Thanks for the report! About the second party processors-I  knew there were operational differences between them and stock cards. I just didn't know if, like say RAM, you could swap out PC133 ram in place of slowere PC100 ram without ill effect. I will read your account and devour it! Thanks for responding, buddy! I'll report back here, after I determine what and how I will do it.

markwlewis wrote:

Well, it seems you upclocked the bus speed in Frankintosh to 133 to take advantage of the speed of the QS processor. Are you saying that you do not recommend that change?

- That is correct. Much of the time, these machines are quite unstable with the bus overclocked. I consider myself lucky. You can try it, if you really want to, as there may be no harm in doing so.
Most likely, if it doesn't work, you just encounter instability. Only once have I heard of any permanent damage arising from overclocking the bus to 133mhz. It all depends on how much work you are willing to put into this, keeping in mind you must completely dissasemble the machine to reach the resistor pads which are used to set the bus speed.

markwlewis wrote:

Would "upclocking" the processor actually create a situation where the processor is running at rated speed, just on the 100mhz bus? That seems like a more stable situation, if I read the comments correctly. The processor I have is a 733. If I understand correctly, if I do nothing but install the processor and hook up the 12 V cable, I get 550 from it, yes?

- Much of the time, you won't get the same speed on the 100mhz bus, but, in most cases, can configure a slightly faster setting ( say, 550 from a Digital Audio's 533 card in a Sawtooth ). You are correct that a 733 would run natively at 550 in your Sawtooth, as it's set at a 5.5:1 ratio.

markwlewis wrote:

If I upclock the CPU card, could I do better than that? (I assume so...) If I upclocked the CPU to the same (appx) speed as it's original rated speed, would it, if all goes well, be about as reliable as the processor would be in the original QS machine? (Just trying to understand this stuff...)

-Yep. You may even be able to go slightly faster, if the processor will handle it, and you provide adequate cooling.

markwlewis wrote:

I found instructions for overclocking the 867 QS cpu here:
http://www.bekkoame.ne.jp/~t-imai/g4de1.html
...my assumption is that both the 733 and 867 are the same board (the "filled" positions in the chart for "733" match my board, R3 and R5). Agree?

If I have this right, I should go for a 7x multiplier if I want to play it safe, maybe 7.5x if I want to push the envelope (although not much of a push, as my math has the desired speed to equal 733 on a 100mhz bus says I should be setting the speed to 974 and actually 1000mhz equivelent is closer than 933. Also, 7.5x requires less modifications--ie:easier-- as the two positions already filled stand and only one additional position would need to be filled?)

-That processor ought to handle 750mhz (7.5) just fine. That's only 27mhz over it's rated speed, which is well under a ten percent increase. And easier is good

 

markwlewis wrote:

Bonehead question: these are just *jumpers* that we are discussing here, right? So all I need do is add a solder "bridge" between the R1 (R3 and R5 are bridged already) to up the multiplier to 7.5x and end up with about 752mhz on the 100mhz bus? Do I actually understand this?

-Essentially, yes, the resistors are equivalent to jumpers. As for the positions, I don't recall, and my drawing are at home ( I'm elsewhere, just now ), but it reads as if you understand things just fine, and a solder bridge will do the job. Again, if 7.5 is easier, then go for it. It certainly should handle it.

markwlewis wrote:

Then, once I add the 12v add-on cable, as you describe, I am probably golden?

Should I add an additional fan to the AGP if I do this, in your opinion?

Once again, ironhawk, thanks for advice and info. It is amazing how much info can be gathered in a short time, when the right people get involved! This "internet" thing may just catch on....

-Yep! A spliced yellow hard drive power cable should do it. When you install the daughter card, in the same manner with which the original was installed, you'll notice an extra hole drilled, intended for a fourth mounting post ( the first three are in a triangular formation ). That hole is where you'll add the 12volts, using the spliced cable ( preferably now ended with an eyehole connector ) a small bolt, and one or two nuts. I took my daughtercard to a hardware store to find the best sized nuts and bolts.

For just a 27mhz increase, a fan may not be needed, but I would, anyways, as CPU fans are fairly inexpensive ( even free, if you have a friend with an old PC ), and it certainly couldn't hurt.

Last edited by ironhawk (2005-05-07 7:41 pm)

I'm not sure if the logic board is indeed incapable of supplying the power via the daughtercard socket, but I know it's not designed to do so, and the daughtercard needs it in order to run.

Anything past ~600mhz won't even boot, to include an overclocked stock Sawtooth or Mystic daughtercard, and I'm pretty sure it's a voltage issue.
Of course, upgrade companies planned for this in their designs. Apple probably never planned for anything past 500mhz to run in these machines.

ironhawk wrote:

Basically, the posts are under the logic board, and match the triangular formation of the screws through the daughtercard, as those screws thread throught the daughtercard and into the support posts, securing it to the very same, and those posts thread through the logic board and into the posts under the logic board, securing it to the tower's steel inner-chasis.

You may want to remove these, and secure the mounting posts to the logic board by using nuts, as I did when moving everything into my new chasis.

The reason for this is, when the 12 volts is connected to the daughtercard, those same support dropouts may provide a short circuit from the 12volts to ground via the chasis.

Are you saying that *all* the dropouts may cause a short, or specifically the one with the power cable connected?

ironhawk wrote:

When I moved everyhting into the G3 chasis, which was without the same dropouts, I experienced no such issues.

It may have been purely coincidental, but I'm thinking not.
If you move ahead with the hack, and find it works fine, in your machine, with the dropouts present, then that's great.
Otherwise, if you find your machine behaves the way mine first behaved, you'll need to break out the tin snips.

So, worst case, I may have to pull the logic board and cut off the support dropouts that match up with the attachment holes on the daughter card? Where it attaches to the logic board with fasteners?

I'm pretty handy with silicone. Once I get the processor pulled out of the Sawtooth, I may be able to better see what I am dealing with. Maybe a small dollop of silicone would do the trick. Unless you are saying that the fasteners, themselves, would cause the short? In any case, thanks for the heads up!