Re: Keeping other stuff with addresses

According to Stefan Monnier  <monnier@iro.umontreal.ca>:

another way to steal bits is over alignment.

Yup.  I keep lamenting that Alpha didn't go for bit-addressed memory,
which would have given us 3 extra free bits from alignment (as well as
allowing pointers to bits and bitfields).

I thought STRETCH persuaded people that bit addressable memory was a bad idea.

>
Yes, but that was a misunderstanding.  I'm not suggesting that
load/store instructions can access things at any bit position and any
bit size.  Any load or store with a pointer whose last 3 bits is not 0 would
presumably signal en error.

Seems like an odd place to put what are in practice just flag bits.

Just like the 21064 Alpha where they had byte-addressed memory but the
load/store instructions could only handle aligned words.

Well, we know how that turned out, not unlike the way IBM designed the 360
to require data alignment, got badly bitten when they realized it broke a
lot of Fortran programs, and added unaligned accesses in the 360/85.

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