Re: [Tuxnes-devel] more help w/ asm

[Jim U. <ji...@3e...>]

At 08:10am on 2001 April 12, Mike Melanson did write:
> On Wed, 11 Apr 2001, Jim Ursetto wrote:

> 	Right. These are all well-known issues with the dyn-rec
> approach.
Well, don't I feel silly now.  I thought the dyn-rec
engine was poorly understood except by the original author.
Glad to hear that.

> > and it's very fast, nearly 10 times faster than the Nofrendo core,
> > using the none renderer.
> 
> 10 times faster? Really? Finally, some real speed comparisons.
> However, how much time does the program spend simulating the 6502 in
> comparison to, say, rendering the graphics 60 times per second?

I think it'd be difficult to get a pure measure of 6502 emulation
speed, unless someone has a long sequence of varied instructions that
don't depend on input or output.  Barring this, I simply used the none
renderer, decoupling it from 60fps vertical refresh by commenting out the 
sync code.  Whenever UpdateDisplayNone() is called, it increments a
global frame count.  Input and output routines are still called
normally, because otherwise the cart wouldn't progress.   The I/O
routines call drawimage, but this is a no-op.  So the approximate
overhead is:

- input and output routines
  - CLOCK, CTNI, VBL, etc. variables updated
  - fiddling based on register
  - drawimage no-op
- interrupt routine
  - CLOCK etc. variables updated
  - UpdateDisplayNone no-op

No rendering is done at all.  The remaining overhead, I suspect is
concentrated in the I/O routines (the "fiddling" part).  Speed-wise,
on a Celeron 366 I get:

dyn-rec engine: 4250 fps
nes6502 core:   600 fps
M6502 core:     440 fps

So let's say 7 times faster.  This was timed several times with Super
Mario Brothers, using the eyeball-and-watch method, over a 1 minute
period, dividing total frames by 60.  Admittedly not the most accurate
method, but gives you a general idea.  At one time I had implemented
an accurate fps counter, but not in this copy of the code.

When rendering is turned on, and synced to refresh, there is no
appreciable difference in rendering speed on my system.  I.e., it runs
at a full 59 or 60 fps at 400x300 (unscaled), when run with full-screen 
DGA or GGI.

However, I haven't done any speed comparisons with rendering on but
without vertical sync.  That might be interesting.

It's too bad I still have that slowdown problem with my Maestro2
soundcard.  It's not as fun without sound...

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