Why hasn’t anyone made a G5 upgrade and is it even possible to upgrade a G4 to a G5?

[Angelgreat]

When the G5 came out, Apple promised a 3ghz PowerMac and G5 iBook and MacBook, but Apple never made one. Apple said there were problems with IBM's manufacturing and the intense power usage, but that has me wondering something.

Why didn't third party companies try to make G5 upgrades for G4 PowerMacs and G4 PowerBooks anyways? Also,

 

[CircuitBored]

Why didn't third party companies try to make G5 upgrades for G4 PowerMacs and G4 PowerBooks anyways?

Because they are entirely different processors. The relationship between the G5 and the G4 is nowhere near as close as the G4 and the G3. The G5 CPU (PPC 970) is basically an entirely different microarchitecture that is software compatible with G4s. Consider that the bus on the slowest G5 machines is 800MHz, whereas on the fastest G4 it was 167MHz. Putting a G5 CPU on a G4 bus would bottleneck it beyond useability.

The CPUs on PowerBook G4s are soldered on, meaning you cannot upgrade the CPU without expert equipment. The PPC 970 is too power hungry for a laptop and it was never designed for anything other than workstation/server use. If Apple couldn't make it work in their own products then there is no way that a separate company could either.

Technical reasons aside: PPC 970s were expensive and yields were low. There weren't that many chips to go around. Apple and IBM likely took up nearly all the stock produced and no third-party company is going to waste money developing a product they can't actually produce.

 

[joshc]

Still want one of these...

 

[Angelgreat]

The CPUs on PowerBook G4s are soldered on, meaning you cannot upgrade the CPU without expert equipment.

Oh wait, you're right. The PowerMac G3 we're the ones who had removable cpu cards. Sorry about that.

 

[Gorgonops]

As noted, the big issue with an upgrade board is the bus is completely, irrevocably different between the 970 and G4. To make it work you'd have to invest in developing an entirely new bus translator chip (essentially a substitute for the CPC925 or CPC945 northbridge chips Apple used in the complete machines) to go between the CPU and the motherboard connector. And in the process of doing that you'd then constrain the 970 to the catastrophically slow (by comparison to the real thing) 133 or 167mhz SDR connection to RAM, etc. It's possible the end result would perform *worse* than the original CPU under those constraints.