alt Hacker News> Each MMX register is 64 bits wide. Internally, the MMX registers were aliases of the x87 floating-point registers.
Due to the way the first Pentium 3 CPUs (Katmai) were built, they likewise aliased the x87 (and thus, MMX) registers to the XMM SSE registers, but this was hidden from programs. It wasn't until at least the Coppermine revision that they were separate registers again.
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userbinator • yesterday at 11:02 PM
It makes it easier to save and restore state when it's basically the same registers used differently.
I remember hearing a rumour as a young teen that the Coppermine codename meant it actually had copper wiring and that's what made it faster somehow. Copper has lower resistance than aluminium and can therefore help chips run faster - it makes sense! But it was just a codename and the coppermine had aluminium interconnects.
My family got a PIII 533Mhz coppermine, in the early sideways Slot 1 configuration. Blazing fast at the time. Been a long time since I heard anyone say "coppermine".
CPU progress was wild in the 90s, where you could wait two years and your new CPU would be double the old one's speed at the same price point. Today it takes near a decade for CPU speed to double.
I also recall the first game that advertised its exciting use of the new MMX technology: POD.[1]
[1] https://en.wikipedia.org/wiki/POD_(video_game)