This thread mentions something about it: "This is probably because those cards use PLDs/FPGAs to interface the processor to the older bus, and they apparently can't operate at 100MHz." Someone more knowledgable might have to chime in with what the reasoning was.
So they added the FPGA so it could be used in the Beige and the B&W/Yikes, it was not a technical limit of the machines themselves, but rather Sonnet didn't want to design two upgrades.
not so sure on this one, this may well be the case, but from what I recall reading many years ago, sonnet themselves claimed it was some sort of errata between the 7450/7455 CPU and the MPC106 itself that prevented them from operating the whole lot at 100Mhz
of course sonnet might of been BSing when they said this to cover their own failings, but at the same I can well belive there being unforseen compatibility issues, the Grackle chip was never officially released in a 100Mhz form to the wider market, I have never been able to find any datasheet on or the such like and all the 100Mhz parts I have seen have been XPC parts, ie that is to say not fully qualified
one card that would be interesting to experiment with here would be, is if I recall correctly the older versions of the Sonnet 7450/7455 700Mhz-1Ghz ZIF CPU's where compatible with the G3 beige *only* so I would guess those dont have whatever logic flips the socket connections around in the later versions that are both G3 beige and Blue and White compatible
but if one of those G3 beige only cards could be inserted into a G3 blue and white motherboard anyways on a test bench (where it dosent matter if its jutting half way out of the motherboard because its designed for a G3 beige actually) might be an interesting test in itself, just make sure to set the CPU PLL accordingly for a 100Mhz bus and see what it does!
I do know that in generally these ZIF's can be run at a 75Mhz bus, so there is a bit of wiggle room
Under the heatsink of an Encore G4/ZIF
So, a couple of months ago I managed to get my hands on a Sonnet Encore G4/ZIF 1GHz, possibly the fastest G4 upgrade for the PowerMac G3 and "Yikes!" G4. I couldn't find any pictures of how the card looked under the heatsink on the Web, so I decided to take some and post them here, as this...
also since I see this question get asked quite a bit, here is a pinout of the power connector on these ZIF's for anyone missing the original wiring loom that would of come with it
Beige G3 + Sonnet Encore ZIF 1ghz will not power on
Hello, I just bought the Sonnet Encore 1ghz ZIF processor upgrade for my Beige G3. When I got it I realized I was missing the power cable adapter which will run a power connector directly to the CPU, which is not normally present. I asked the seller and they do not have it(see attached) The 8...
68kmla.org
(although it would be good to get a 2nd source on that, if someone who does have a loom could indeed confirm or deny the pinout above)
and also here is a bus speed jumper setting guide for the G3 blue and white/Yikes!
