home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
The Datafile PD-CD 5
/
DATAFILE_PDCD5.iso
/
utilities
/
f
/
frodo
/
Docs
/
frodosc_ht
< prev
next >
Wrap
Text File
|
1995-09-18
|
2KB
|
45 lines
<HTML>
<HEAD>
<TITLE>Frodo SC</TITLE>
</HEAD>
<BODY>
<H1>The single-cycle emulation 'Frodo SC'</H1>
<HR>
<STRONG>Frodo SC</STRONG> 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 ø2 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 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>Color of $ff bytes read by VIC when BA is low and AEC is high is not correct
<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>Some opcodes like $8b/$ab don't create the same (partly unpredictable) results as on a real 6510
<LI>BRK cannot be interrupted by IRQ/NMI
<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>