[min_max9000]

I have a Fastmac 7455 1.2 GHz 2 MB L3. Is it possible, via the jumpers on the card, to ramp up the speed at all? Perhaps to 1.4 GHz or 1.5 GHz?

Thanks in advance

[harrisjamieh]

Even if it is, is there much point just to get an extra 2/300 Mhz

[min_max9000]

Worth it to me or I wouldn't have asked. Anyone else know? Is there a difference in the 7455 chip they put in the 1.2 vs the 7455 chip they put in the 1.5? Is there such a difference or are all 7455 chips made the same?

[Lateralus]

2/300MHz is pretty nice overclock when you're in the 1GHz range, I'd consider it very worthwhile.

One thing you may want to find out is whether your G4 is a 7455A or 7455B. The 7455As were the first generation 7455s and didn't overclock well at all. The 7455B, on the other hand, has become one of the Mac world's most famous overclockers. If it's a 7455B and it's rated for 1.2GHz by Motorola, then 1.4GHz~ should be very attainable.

FastMac/OWC upgrades feature a dipswitch bank for manually selecting the processor speed. Your package should have include a diagram of the supported settings. If you don't have it, just fire an e-mail to OWC or FastMac.

[min_max9000]

Originally Posted by Lateralus

2/300MHz is pretty nice overclock when you're in the 1GHz range, I'd consider it very worthwhile.

One thing you may want to find out is whether your G4 is a 7455A or 7455B. The 7455As were the first generation 7455s and didn't overclock well at all. The 7455B, on the other hand, has become one of the Mac world's most famous overclockers. If it's a 7455B and it's rated for 1.2GHz by Motorola, then 1.4GHz~ should be very attainable.

FastMac/OWC upgrades feature a dipswitch bank for manually selecting the processor speed. Your package should have include a diagram of the supported settings. If you don't have it, just fire an e-mail to OWC or FastMac.

Worthwhile indeed. I got impatient waiting for answers from various forums so I went ahead and moved some jumpers. I went straight to 1.5 at first, but crashed twice in about 5 minutes. I have now had it at 1.4 for the last 18 hours or so, and I have not come across any issues yet. I picked up about 6% on my Xbench score and VNC is remarkably better. Photoshop is much nicer to use as well. Well worth the 200 MHz in my book. If anyone knows a way to get it stable at 1.5, I would be really grateful. The difference between 1.4 and 1.5 was notable also.

[Lateralus]

The main thing stopping you from achieving 1.5GHz is insufficient voltage. GigaDesigns CPUs have a dipswitch bank for selecting the clock speed and another for selecting the voltage. FastMac CPUs, however, only allow manual selection of the clock speed.

The only way to increase the voltage on your CPU would be to have some fun with a soldering iron. But I wouldn't count on knowing what exactly solder since the voltage settings are proprietary between the CPU card manufacturers and the chances of FastMac telling you their settings is pretty much zero.

I'd just be happy with 1.4GHz if I were you.

[newtech]

PPC7455B chips come in 1000Mhz, 1250MHZ and 1400MHz. in my experience the 1000 and 1250 are clockable to 1333 but not much more, the 1400 seems to work often to 1583.