Re: 80286 protected mode

On Sun, 13 Oct 2024 19:43:34 GMT
scott@slp53.sl.home (Scott Lurndal) wrote:

Brett <ggtgp@yahoo.com> writes:

David Brown <david.brown@hesbynett.no> wrote: 

 

All I am asking Mitch to do is to understand this, and to stop
saying silly things (such as implementing memmove() by calling
memmove(), or that the /reason/ you can't implement memmove()
efficiently in portable standard C is weaknesses in the x86 ISA),
so that we can clear up his misunderstandings and move on to the
more interesting computer architecture discussions. 

 <snip>

My 66000 only has one MM instruction because when you throw enough
hardware at the problem, one instruction is all you need.
>
And it also covers MemCopy, and yes there is a backwards copy
version.
>
I detailed the hardware to do this several years ago on Real World
Tech. 

 
Such hardware (memcpy/memmove/memfill) was available in 1965 on the
Burroughs medium systems mainframes.   In the 80s, support was added
for hashing strings as well.
 
It's not a new concept.  In fact, there were some tricks that could
be used with overlapping source and destination buffers that would
replicate chunks of data).

The difference is that today for strings of certain size, say from 200
bytes to half of your L1D cache, if your precios HW copies less than 50
bytes per clock then people would complain that it is slower than snail.