Absolutely true. I wasn't thinking along those lines.Analog Kid said:You've left out the bit about emulating 68000 code on a PowerPC which is very far from trivial...
Fortunately, Apple had a huge speed advantage to leverage when they wrote that emulator. The slowest PowerMac ever built (a PM 6100) was a 60MHz PPC 601. This is substantially faster than the fastest 68K box ever built (a Quadra 840av) with its 40MHz 68040. A 50% increase in clock speed, plus a more efficient architecture gave Apple enough headroom to write a 68K emulator that would always perform at least as fast as actual 68K boxes.
But even with those advantages, you're right - it must've been a bear to get the system working and stable. Although lots of people have written emulators, one that works well enough to run legacy device drivers (as Apple's can do) is very difficult to get right.
We will have to agree to disagree here.Analog Kid said:Again, my thesis here is that different chips are better for different applications. I think 64bits just won't be right for a laptop until the memory is needed, and when it is I think there will be a better portable solution than the G5. The philosophy of the G5 seems to have been performance at the expense of power, which doesn't seem right for a laptop. You can bring the power down by tweaking it, but you could still get a better laptop design with a different architecture while keeping performance degradation limited.
While I agree that power consumption is critical for a laptop, I am confident that IBM will have lower-power G5-class chips in the future.
I think your criticism of the "G5" is really a criticism of the PPC 970. It is likely that all of IBM's forthcoming 64-bit PPC chips, including any low-power versions, will be called "G5" by Apple (until some future change is substantial enough to deserve a "G6" moniker.) I think a hypothetical PPC 970LC (or whatever they end up calling it), designed for low power consumption will work well in a laptop.
Although I agree 64 bit apps are rarely necessary for a laptop user, I disagree that having a 64 bit processor is in any way detrimental. Especially if the chip is capable of running 32-bit apps without an emulation layer. (The OS doesn't necessarily have to be built around 64-bit code to support 64-bit apps - it only has to provide 64-bit APIs and have a memory manager that can manipulate 64-bit page tables.)