Previous Thread
Next Thread
Print Thread
Page 5 of 7 1 2 3 4 5 6 7
Re: cpc 6128 - demo [Re: Breiztiger] #115032 04/13/19 10:53 AM
Joined: Nov 2010
Posts: 84
Breiztiger Offline OP
Member
OP Offline
Member
Joined: Nov 2010
Posts: 84
hi

z80 test error report bug in that test

http://www.cpc-power.com/index.php?page=detail&onglet=dumps&num=12883

SCF and CCF instructions

Re: cpc 6128 - demo [Re: Breiztiger] #115033 04/13/19 11:09 AM
Joined: Aug 2015
Posts: 387
Edstrom Offline
Senior Member
Offline
Senior Member
Joined: Aug 2015
Posts: 387
I think this a known variant issue according to MAMEtesters: https://mametesters.org/view.php?id=2701 did you request a followup there?

Re: cpc 6128 - demo [Re: Breiztiger] #115034 04/13/19 11:16 AM
Joined: Mar 2001
Posts: 16,535
R
R. Belmont Online Content
Very Senior Member
Online Content
Very Senior Member
R
Joined: Mar 2001
Posts: 16,535
Yeah, we're emulating the NEC Z80, which in this case has that difference from the Zilog original.

Re: cpc 6128 - demo [Re: Breiztiger] #115035 04/13/19 12:13 PM
Joined: Nov 2010
Posts: 84
Breiztiger Offline OP
Member
OP Offline
Member
Joined: Nov 2010
Posts: 84
Sorry it seem to be that issue

Re: cpc 6128 - demo [Re: Breiztiger] #115036 04/13/19 12:21 PM
Joined: May 2004
Posts: 1,615
H
Haze Offline
Very Senior Member
Offline
Very Senior Member
H
Joined: May 2004
Posts: 1,615
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...

Re: cpc 6128 - demo [Re: Breiztiger] #115037 04/13/19 02:10 PM
Joined: Mar 2002
Posts: 1,156
H
hap Offline
Very Senior Member
Offline
Very Senior Member
H
Joined: Mar 2002
Posts: 1,156
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?

Re: cpc 6128 - demo [Re: Breiztiger] #115038 04/13/19 05:38 PM
Joined: Mar 2001
Posts: 16,535
R
R. Belmont Online Content
Very Senior Member
Online Content
Very Senior Member
R
Joined: Mar 2001
Posts: 16,535
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.

Re: cpc 6128 - demo [Re: Breiztiger] #115039 04/13/19 05:59 PM
Joined: Mar 2002
Posts: 1,156
H
hap Offline
Very Senior Member
Offline
Very Senior Member
H
Joined: Mar 2002
Posts: 1,156
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.
Re: cpc 6128 - demo [Re: Breiztiger] #115040 04/13/19 06:39 PM
Joined: Aug 2015
Posts: 387
Edstrom Offline
Senior Member
Offline
Senior Member
Joined: Aug 2015
Posts: 387
Maybe a lot of arcades just starts working if we implement the NEC variation? :-)

Re: cpc 6128 - demo [Re: Breiztiger] #115041 04/13/19 07:12 PM
Joined: Mar 2001
Posts: 16,535
R
R. Belmont Online Content
Very Senior Member
Online Content
Very Senior Member
R
Joined: Mar 2001
Posts: 16,535
No known software other than this test program cares about this difference smile

Page 5 of 7 1 2 3 4 5 6 7

Who's Online Now
4 registered members (Lord Nightmare, R. Belmont, judge, robcfg), 53 guests, and 3 spiders.
Key: Admin, Global Mod, Mod
ShoutChat Box
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Forum Statistics
Forums9
Topics8,789
Posts115,687
Members4,908
Most Online890
Jan 17th, 2020
Powered by UBB.threads™ PHP Forum Software 7.7.3