I remember hearing years ago from IBM that 64-bit mode programs tended
to run slightly slower than those running in 31-bit mode.
At the time, I assumed the reason was that programs using 8-byte
pointers and integer values use more cache lines and 4K pages/frames
than programs using 4-byte valu
I thought I heard that the additional translation tables involved for
64-bit address made DAT take longer. Whether that involved additional
pipeline stages I don't know.
I have not seen any documentation that the same instruction that doesn't
involve addresses takes long under 64-bit vs. 31-bit,
AFAIK, there is no reason to expect that the execution of a 64-bit instruction
takes any longer than the execution of an equivalent 32-bit instruction. For
example, the execution of the 32-bit ADD (AR) instruction should be comparable
to the execution of the 64 bit ADD (AGR).
However, the astut
On Thu, 6 Jun 2024 at 23:55, Dan Greiner wrote:
> AFAIK, there is no reason to expect that the execution of a 64-bit
> instruction takes any longer than the execution of an equivalent 32-bit
> instruction. For example, the execution of the 32-bit ADD (AR) instruction
> should be comparable to the
