mirror of
https://github.com/Oibaf66/frodo-wii.git
synced 2024-11-26 21:44:22 +01:00
77 lines
2.5 KiB
HTML
77 lines
2.5 KiB
HTML
|
<HTML>
|
|||
|
|
<HEAD>
|
|||
|
|
<TITLE>Frodo, Frodo PC and Frodo SC</TITLE>
|
|||
|
|
</HEAD>
|
|||
|
|
<BODY>
|
|||
|
|
|
|||
|
|
<H1>Frodo, Frodo PC and Frodo SC</H1>
|
|||
|
|
|
|||
|
|
<HR>
|
|||
|
|
|
|||
|
|
Frodo comes in three 'flavours' that allow you to decide between speed
|
|||
|
|
and accuracy of the emulation.
|
|||
|
|
|
|||
|
|
<H2>The line-based emulation 'Frodo'</H2>
|
|||
|
|
|
|||
|
|
<B>Frodo</B> is a line-based emulation, i.e. the activities that happen
|
|||
|
|
in parallel during one video line in the real C64 are emulated one after
|
|||
|
|
the other for the different chips. This offers a reasonable degree of
|
|||
|
|
precision of the emulation at a decent speed. There are some things that
|
|||
|
|
cannot be emulated with this technique, but it works fine with about
|
|||
|
|
80% of all C64 programs and it is also the fastest of the three Frodo
|
|||
|
|
versions.
|
|||
|
|
|
|||
|
|
<HR>
|
|||
|
|
|
|||
|
|
<H2>The improved line-based emulation 'Frodo PC'</H2>
|
|||
|
|
|
|||
|
|
<B>Frodo PC</B> is also a line-based emulation but it has some improvements
|
|||
|
|
over the standard Frodo:
|
|||
|
|
|
|||
|
|
<UL>
|
|||
|
|
<LI>Code in chip registers can be executed
|
|||
|
|
<LI>Correct calculation of 6510 instruction cycles
|
|||
|
|
<LI>More precise CIA emulation
|
|||
|
|
</UL>
|
|||
|
|
|
|||
|
|
Programs that don't work on the standard Frodo or that produce an
|
|||
|
|
"Illegal jump to I/O space" message might work with Frodo PC. However,
|
|||
|
|
Frodo PC is a bit slower.
|
|||
|
|
|
|||
|
|
<HR>
|
|||
|
|
|
|||
|
|
<H2>The single-cycle emulation 'Frodo SC'</H2>
|
|||
|
|
|
|||
|
|
<B>Frodo SC</B> is a special version of Frodo that doesn't work with a
|
|||
|
|
line-based emulation but instead with a cycle-based one. That means that
|
|||
|
|
the emulator switches between 6510 and VIC in every emulated <20>2 clock
|
|||
|
|
phase. By doing this, Frodo SC achieves an extreme precision (nearly all
|
|||
|
|
$d011 and $d016 effects can be emulated), but at the expense of speed.
|
|||
|
|
|
|||
|
|
In the settings options, Frodo SC differs from Frodo/Frodo PC in only
|
|||
|
|
a few points:
|
|||
|
|
|
|||
|
|
<UL>
|
|||
|
|
<LI>The "Cycles per line" settings are not available as the timing of Frodo SC is hardcoded
|
|||
|
|
<LI>The "Clear CIA IRC on write" hack is not necessary
|
|||
|
|
</UL>
|
|||
|
|
|
|||
|
|
Apart from that, Frodo SC is operated in the same way as Frodo and also
|
|||
|
|
uses the same settings. Frodo SC has only a few incompatibilities to a
|
|||
|
|
real C64:
|
|||
|
|
|
|||
|
|
<UL>
|
|||
|
|
<LI>On the left and right side of the screen, sprites are not clipped but blanked out
|
|||
|
|
<LI>Sprite collisions are only detected within the visible screen area (excluding borders)
|
|||
|
|
<LI>The sprite data fetch ignores the state of BA
|
|||
|
|
<LI>On BA low and AEC high, the VIC always reads $f in D8-D11
|
|||
|
|
<LI>Color register modifications are visible 7 pixels too late
|
|||
|
|
<LI>The TOD clock should not be stopped on a read access, but be latched
|
|||
|
|
<LI>The SDR interrupt is faked
|
|||
|
|
<LI>Some small incompatibilities with the CIA timers
|
|||
|
|
<LI>The readable SID registers are not emulated correctly
|
|||
|
|
</UL>
|
|||
|
|
|
|||
|
|
</BODY>
|
|||
|
|
</HTML>
|