Holger Bettag writes:

"Albert D. Cahalan" [off-list ref] writes:

quoted

Now do an unconditional 64-bit byte swap on the motherboard.
Consider an array of four __u16 values affected by this.
They get converted from big-endian to little-endian, and they
get moved to different addresses. Excellent! All the weirdness
just cancels out, giving perfect little-endian. This works for
8-bit, 16-bit, 32-bit, and 64-bit data. Life is good.

Does it work for 128 bit data? The 74x0's most promiment feature,
AltiVec, would expose a strange mixed endianness to programmers
otherwise.

Yes. Motorola noticed this problem, and added a built-in swap
to fix the problem. See page 3-6, section 3.1.4, figure 3-5 in
ALTIVECPEM.pdf, the "AltiVec Technology Programming Environments
Manual". Unaligned vectors don't work in big-endian or little-endian
mode, and the code needed to load them is equally long.


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