amigadave wrote:
downix wrote:
.... The 68060 used such a system to it's proto-coldfire core, so much so that my college professor put that the coldfire was just the 060 w/ that translator removed.
I am trying to wrap my limited CPU knowledge mind around that statement. 68060 proto-coldfire core??? hmmmm .... I thought that the coldfire came out after the 68060 and it was a stripped down design with less instructions that met the embedded market demands of the time?
The term 68060 proto-coldfire core sounds to me (the average layman) like a part of the 68060 designed to copy a pre-existing coldfire CPU? Is this an Egg or the Chicken question, which came first, the 060 or the coldfire? I guess the coldfire could have as the 68000 series was on its way out and Macs were already moving to the PPC, which is why no Macs ever came from Apple with the 060 inside.
Sorry, just rambling to myself.
Fundimentally, the 68060 uses a microcode-retranslation system paired up to a reduced-OPcode core, using hardware to translate the instructions that the core cannot natively run into ones that it can. The majority do just go through, but a few needed translating. This is how every high-speed CISC CPU has worked since the 68060. In the intel world the first was the NexGen 5x86, for example.
What my professor theorized was that despite PowerPC taking over the desktop arena, Mot had enough existing 68k customers to support that it turned an eye to how to advance the m68k without hurting it's new PowerPC strategy. The Motorola engineers basically removed this microcode stage from the m68060 and with a little work, viola, you have the Coldfire. That way, their performance customers, such as Apple, wouldn't be upset that Motorola was hurting their migration by releasing faster CPU's of the old-family, but Motorolas embedded customers would still get the product they needed.
