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Re: cpc 6128 - demo
[Re: Breiztiger]
#115034
04/13/19 11:16 AM
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Joined: Mar 2001
Posts: 16,394
R. Belmont
Very Senior Member
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Very Senior Member
Joined: Mar 2001
Posts: 16,394 |
Yeah, we're emulating the NEC Z80, which in this case has that difference from the Zilog original.
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Re: cpc 6128 - demo
[Re: Breiztiger]
#115035
04/13/19 12:13 PM
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Joined: Nov 2010
Posts: 84
Breiztiger
OP
Member
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OP
Member
Joined: Nov 2010
Posts: 84 |
Sorry it seem to be that issue
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Re: cpc 6128 - demo
[Re: Breiztiger]
#115036
04/13/19 12:21 PM
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Joined: May 2004
Posts: 1,601
Haze
Very Senior Member
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Very Senior Member
Joined: May 2004
Posts: 1,601 |
Yeah, we're in C++ land these days tho, so creating a derived type with different behavior is far easier than 99% of what goes into MAME...
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Re: cpc 6128 - demo
[Re: Breiztiger]
#115037
04/13/19 02:10 PM
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Joined: Mar 2002
Posts: 1,116
hap
Very Senior Member
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Very Senior Member
Joined: Mar 2002
Posts: 1,116 |
TODO notes in z80.cpp: "This Z80 emulator assumes a ZiLOG NMOS model." (not NEC)
and regarding SCF/CCF flags: "However, people from the Speccy scene mention that SCF/CCF X/Y results are inconsistent and may be influenced by I and R registers." - so, is it wise to base NEC Z80 on SCF/CCF X/Y differences?
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Re: cpc 6128 - demo
[Re: Breiztiger]
#115038
04/13/19 05:38 PM
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Joined: Mar 2001
Posts: 16,394
R. Belmont
Very Senior Member
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Very Senior Member
Joined: Mar 2001
Posts: 16,394 |
The z80.cpp notes are from like 1997. I would believe the newer results from the 2018 test program over them. Also, MAME was arcade-only forever, and arcade games almost always used the NEC D780, so it's not shocking we ended up modeling it instead of Zilog.
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Re: cpc 6128 - demo
[Re: Breiztiger]
#115039
04/13/19 05:59 PM
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Joined: Mar 2002
Posts: 1,116
hap
Very Senior Member
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Very Senior Member
Joined: Mar 2002
Posts: 1,116 |
Those notes are old yes, more like 2008 or so. I don't know of other NEC vs Zilog differences, but regarding SCF/CCF X/Y flags we definitely emulate the Zilog. *edit* according to http://www.cpcwiki.eu/forum/technical-support/z80-defective-tests/ it fails on a real Zilog.
Last edited by hap; 04/13/19 06:16 PM.
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Re: cpc 6128 - demo
[Re: Breiztiger]
#115040
04/13/19 06:39 PM
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Joined: Aug 2015
Posts: 381
Edstrom
Senior Member
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Senior Member
Joined: Aug 2015
Posts: 381 |
Maybe a lot of arcades just starts working if we implement the NEC variation? :-)
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Re: cpc 6128 - demo
[Re: Breiztiger]
#115041
04/13/19 07:12 PM
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Joined: Mar 2001
Posts: 16,394
R. Belmont
Very Senior Member
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Very Senior Member
Joined: Mar 2001
Posts: 16,394 |
No known software other than this test program cares about this difference 
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