Amiga One (G3/G4) vs. Power Mac G3/G4

[Floid]

kubyx wrote:
Other than the name what is the main difference between the, G3/G4 Power Mac and the G3/G4 Amiga One?

I've been wondering this for along time now.  :-?

Everything but the CPU.

Apple has relied on Motorola (and IBM?) northbridges, recently going to their own(?) custom designs with the need for things like DDR SDRAM support.  The present Mai (A1, Pegasos) chipset is arguably a generation behind, not that it matters altogether much for processors of current speed grades.  The northbridge is what interfaces the processor to system memory and buses (PCI, AGP... and things like PCI-X, Hypertransport, and V-Link in the case of various 'modern' x86 chipsets.)

In turn, the southbridges and other 'peripheral' chips are what provide UATA (also known as 'Ultra DMA' IDE), USB, ethernet, legacy ports, onboard AC97 sound, and so on.  Apple has rolled their own for a few generations; Eyetech and Genesi both use chips from Via, of slightly different model.

Macs use OpenFirmware boot ROMs/"BIOS"es - OF is basically a small, special-purpose FORTH system, 'easily' implemented for various hardware, and designed to identify peripherals and get an OS kernel loaded from disk.  'Old World' PowerPC Macs still had custom ROMs, offering OF as a compatibility option (for Apple's UNIX, the never?-released PowerPC OS/2, Linux, etc); 'New World' machines seem to be OF-only, but I'm not 100% sure.  (Apple specifically defines 'New World' something like 'including OpenFirmware 3.x.')  OF is an open *specification.*

The AmigaOne uses code from the U-Boot (formerly PPCBoot) project instead; U-Boot/PPCBoot is *open source.*  In the case of the Pegasos, Genesi have licensed an OpenFirmware implementation from a vendor specializing in such (similar to the way x86 boardmakers license BIOSes from AMI, Award, or Phoenix).

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Performance-wise, what're the differences?  For that, you'd need benchmarks (some are floating around, mostly based on the 'RC5' distributed crypto-cracking engine, not very representative of more standard workloads), but for the models of Mac produced using the models of CPU offered for the AmigaOne (iMac/iMac2/"Snow" Powerbook/eMac), it's probably Pretty Darn Close either way.  Any eventual 'G5' Macs would and should blow this hardware out of the water, but it's not like Mai (or Marvell, the vendor Genesi are moving to for the Peg2) aren't aware of IBM's chip roadmaps- by the time a G6 rolls around, Apple and "3rd-party" platforms should be in sync. :python:

[Floid]

The biggest potential difference would be the DDR support on the newer, high-end Macs.  However, the performance benefit is marginal, given that you need dual processors (at current PowerPCs' ~133MHz single-rate buses) to begin to take advantage of that doubled rate.

The second comment on this article does illustrate why DDR isn't a *total* washout; if you recall, the original Amiga chipset was able to use the same trick to get 'free' memory access around the CPU.  In today's world, that's less Magical Apple Engineering than The Way Computers Work; I could have the same "benefit" if I underclocked my K6-2's FSB to 50MHz and told it to keep the PC100 running full-speed asynchronously.  (Yes, this option was available; no, it certainly wouldn't improve I/O performance- CPUs with fast FSBs can still do this thing called 'waiting,' and then they get to run at full-bore when not contending with anything else.)

Edit: Should you buy it?  Depends if you want a Mac, an OS4 Amiga, or a Linux machine, obviously.  I'd be inclined to answer "No, Yes, Maybe," respectively.