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Revision: 1.3
Committed: 2010-04-25T11:52:11Z (12 years, 7 months ago) by cebix
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# Content
1 <HTML>
2 <HEAD>
3 <TITLE>Frodo and Frodo SC</TITLE>
4 </HEAD>
5 <BODY>
7 <H1>Frodo and Frodo SC</H1>
9 <HR>
11 Frodo comes in two 'flavours' that allow you to decide between speed
12 and accuracy of the emulation.
14 <H2>The line-based emulation 'Frodo'</H2>
16 <B>Frodo</B> is a line-based emulation, i.e. the activities that happen
17 in parallel during one video line in the real C64 are emulated one after
18 the other for the different chips. This offers a reasonable degree of
19 precision of the emulation at a decent speed. There are some things that
20 cannot be emulated with this technique, but it works fine with about
21 80% of all C64 programs and it is also the faster of the two Frodo
22 versions.
24 <HR>
26 <H2>The single-cycle emulation 'Frodo SC'</H2>
28 <B>Frodo SC</B> is a special version of Frodo that doesn't work with a
29 line-based emulation but instead with a cycle-based one. That means that
30 the emulator switches between 6510 and VIC in every emulated 2 clock
31 phase. By doing this, Frodo SC achieves an extreme precision (nearly all
32 $d011 and $d016 effects can be emulated), but at the expense of speed.
34 In the settings options, Frodo SC differs from Frodo in only a few points:
36 <UL>
37 <LI>The "Cycles per line" settings are not available as the timing of Frodo SC is hardcoded
38 <LI>The "Clear CIA IRC on write" hack is not necessary
39 </UL>
41 Apart from that, Frodo SC is operated in the same way as Frodo and also
42 uses the same settings. Frodo SC has a few known incompatibilities to a
43 real C64:
45 <UL>
46 <LI>On the left and right side of the screen, sprites are not clipped but blanked out
47 <LI>Sprite collisions are only detected within the visible screen area (excluding borders)
48 <LI>The sprite data fetch ignores the state of BA
49 <LI>On BA low and AEC high, the VIC always reads $f in D8-D11
50 <LI>Color register modifications are visible 7 pixels too late
51 <LI>The TOD clock should not be stopped on a read access, but be latched
52 <LI>The SDR interrupt is faked
53 <LI>Some small incompatibilities with the CIA timers
54 <LI>The readable SID registers are not emulated correctly
55 </UL>
57 </BODY>
58 </HTML>