Superficially, the only major difference you may have to deal with is the presence of an extended BAT implementation on the MPC7445 and above - 8 IBATs and 8 DBATs instead of the usual 4, and an extra protection mode setting, and larger block sizes (up to 4GB) to suit the 36-bit physical addressing mode. It can do TLB searches in hardware, too (not sure if the G3 models can).
I am not sure they're even used after VOF has done it's bit. Then there's little things which are totally optional like power management, the performance counters, instruction cache throttle, essentially you can run it like a 603e or G3 with a few minor quirks - and Solaris PPC already did this years ago, so I think you're basically all set. As long as no particularly G4-specific stuff has been implemented in the mean time (some of which would actually even break old G4 models) it should just boot and go. Your main problem supporting the Mac is those crazy Apple chipsets, I'd say the best place to look is the NetBSD pmac port. -- Matt Sealey <matt at genesi-usa.com> Genesi, Manager, Developer Relations John Sonnenschein wrote: > Heya. > > Does anyone happen to know the significant differences between the G3 > and the G4 as far as they relate to this project? > > Reason I ask is that while I know it'd be great if we had an infinite > supply of ODW's, we don't. Polaris /has to/ run on plain OFW powerpc. > There's no way around that, no matter how much we may wish it to be > so. We simply cannot make forward progress without a cheap, plentiful > development platform. > > However, PS3's and g4 powermacs are still on the expensive side. I > can't afford one in either case. What I can afford though is an old > newworld G3 machine ( bondi imac or similar ) , they can be had for > under $50 these days. I've given up hope trying to get my 44p booting > off the net, and I don't know where to begin coaxing GRUB2 on to the > thing. I've successfully netbooted a powermac ( mac mini actually... ) > before, so I know apple's OFW implementation works. I was thinking > then of picking up some ancient apple kit & having a go at making it > work properly. > > So, hence my question if anyone knows. The significant difference > between a G3 and a G4 ( aside from altivec ) is? > > Cheers > -John >
