Re: 64/65 Cycle Rule?

[steve@dosius.zzn.com (Dosius)]

Sheldon Simms <sheldonsimms@yahoo.com> wrote in message news:<pan.2003.08.24.04.13.18.864830@yahoo.com>...
> On Sat, 23 Aug 2003 20:48:51 -0500, Bryan Parkoff wrote:
> 
> > The problem is that Emulator has to use serial instead of parallel so
> > 6502 CPU must be executed first before Video must be executed second at
> > another time so they can't be done at same time.
> >     Have someone tried to use MMX or SIMD Technology that will help Emulator
> > to run faster without needing to have turn by turn between 6502 CPU and
> > Video.
> 
> I question whether SIMD instructions will help, because to emulate
> Apple II video, you have to do a lot of bit twiddling operations on
> single bytes.
> 
> My IIe emulator maintains an emulated raster beam and, after every
> instruction, updates the portion of the video screen scanned by the
> beam during the execution of the instruction. With appropriate checks
> to make sure that you aren't redrawing unchanged pixels, this approach
> is fast enough. As an example, my emulator runs at around 45Mhz on my
> Athlon XP 1800+ and at around 8Mhz on a Pentium II/300.

Sounds about right, EMU][ achieved about 2.3 MHz on a 486/133, and it
uses a virtual raster beam.

(btw, I wonder how fast a dynamically recompiling 6502 core might run.
:))

-uso.