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Forums > CSDb Discussions > C64 Emulator Bugs
2007-06-24 03:16
chatGPZ

Registered: Dec 2001
Posts: 11351
C64 Emulator Bugs

after stumbling about a bunch of VICE bugs myself in the last couple of days i have decided to compile a list with issues current emulators have. the goals for this are

- make people aware that emulators are by far not perfect (yet?)
- make it easier for emulator authors to improve the emulators, by showing problematic programs and possibly provide simple testcases
- allow c64 coders to implement emulator detection if desired

so well, check this: http://hitmen.c02.at/files/docs/c64/c64_emulator_bugs.txt

help welcomed :)
 
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2007-07-19 09:48
assiduous
Account closed

Registered: Jun 2007
Posts: 343
A new version of Hoxs64 has been released, it can now handle the following titles:

-Aurora 90% ($01 fading corrected, passes the emu check, there's no need to press run/stop to proceed at the beginning anymore)
-Locomotion/Hitmen (IRQ timing adjusted, works now)
-Demo IV (it doesn't crash anymore and flickers in the same manner my C64C does)

The updated emu check list:

Y - test passed, N - emu detected

			CCS	VICE	Hoxs64
Cucumber Juice 2	Y	Y	Y
Deus Ex Machina		Y	Y	Y
Demus Interruptus	Y	Y	Y
+h Emu-Fuxx0r v1	N	N	Y
+h Emu-Fuxx0r v2	Y	N	Y
Waveform Composer	Y	N	Y
Aurora 90%		N	N	Y
Krestage 3		Y	N	Y

valid for: CCS64 v3.3, VICE v1.21, Hoxs64 v1.0.4.24

Ipso facto, Hoxs64 becomes the first C64 emulator to be undetectable by any emu check known to date. \o/
2007-07-19 10:25
JackAsser

Registered: Jun 2002
Posts: 2014
Is it fair to use the 1541 as EMU faxxor? It's very simple to set up some drive code that would rely on the analogue properties of the serial cable, which would be tricky to emulate. It's all a very simple test which I implemented some years ago. Simply generate a square waveform from the drive to the C64 in f.e. 1KHz. Sample this waveform on the C64 in a much higher frequency. In a pure digital world (Emulator) you would count equally many zeros as ones but in the real world this number will differ greatly due to the CMOS logic levels and charge times.

Anyways, requiring a 1541 for EMU-detection is a bit cheaty imo. ;D
2007-07-19 12:06
Graham
Account closed

Registered: Dec 2002
Posts: 990
It's also dangerous, because different drives might behave different. There's also 1541 compatible non-Commodore drives.
2007-07-19 12:18
JackAsser

Registered: Jun 2002
Posts: 2014
Quote: It's also dangerous, because different drives might behave different. There's also 1541 compatible non-Commodore drives.

Agreed, but thing is that on an emulator the ratio is EXACTLY 50/50 but on the real thing it'll never be like that.
2007-07-19 12:51
chatGPZ

Registered: Dec 2001
Posts: 11351
i'd say: do it :) a perfekt emulator also emulates all the weird analog quirks :)
2007-07-19 13:14
enthusi

Registered: May 2004
Posts: 677
the Aurora check in principle is pretty analogous as well. Didnt think it would 'fall' so soon actually :) and I doubt it's beaten yet. The behaviour of those unused bits is correlated to chip-temperature as yago pointed out :)
2007-07-19 14:07
Oswald

Registered: Apr 2002
Posts: 5086
emu fuxxoring only shrinks the audience. and makes you and your emu detection ridiculous in a few years.
2007-07-19 14:47
chatGPZ

Registered: Dec 2001
Posts: 11351
no way it could lead to better emus, god forbid /o\
2007-07-19 16:40
assiduous
Account closed

Registered: Jun 2007
Posts: 343
"*** [vice 1.21] strange issues with $01
seems that switching $01 quickly makes VICE make mistakes in thinking what is RAM and what is ROM...
Interestingly, this one fucks up in WinVICE v1.20 at max. speed and warp mode, but not @ 100% speed.
Brings up (a seemingly long-time known bug) that toggling RAM/ROM quickly (init tune at $E000) confuses VICE.
Zax-Ripp #006/Hurricane http://noname.c64.org/csdb/release/?id=44749"

A: I cannot reproduce it. The warp mode is turned on, the maximum speed is there, it just doesn't fuck up - neither in the interpolating SID sampling mode (at 800% speed), nor in the fast sampling one (3200%).

"- [vice] Non Plus Ultra 64%/Singular http://noname.c64.org/csdb/release/?id=32442"

A: Rule of thumb #3: "switch virtual device traps off".

"- [vice] Alternate Reality/Mr. Zeropage Alternate Reality - City
hangs after the character selection/randomizing"

A: There's only 1 disk side to download, where are the others? Fails on the real thing too.

*** [vice] unidentified problems
- Brutal Blue/Orbs Brutal Blue
"Had some problems with the loader. I remember this working on an older version of Vice though."

A: Doesn't work on the real thing, which indicates there was a problem with an older version of VICE.
2007-07-19 17:01
assiduous
Account closed

Registered: Jun 2007
Posts: 343
Quote: The interlaced girl in the demo Tsunami features 8 bad pixels on her nose when running on VICE (as HCL stated in the note IIRC)

Well spotted, the glitch is visible in Hoxs64 too. CCS64 v3.3 isn't affected by this.

Quote:
the Aurora check in principle is pretty analogous as well. Didnt think it would 'fall' so soon actually :) and I doubt it's beaten yet. The behaviour of those unused bits is correlated to chip-temperature as yago pointed out :)

This one's beaten to death. :) You could measure the fading time multiple times and then check if the values differ, but you can't possibly verify if even values indicate a coincidence or an emulator. And even if you could, it should pose no challenge to randomize the values in some specified range. More attempts to exploit this (or any other oddity that isn't emulated exactly) would be quite useful though. Something along the lines of "detect Hoxs64 compo" should be organized to promote this kind of art. ;)
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