It is currently Mon Dec 18, 2017 12:19 am

All times are UTC - 7 hours





Post new topic Reply to topic  [ 70 posts ]  Go to page Previous  1, 2, 3, 4, 5
Author Message
 Post subject: Re: CPU timing precision
PostPosted: Sun Dec 27, 2015 3:50 am 
Offline
Formerly Fx3
User avatar

Joined: Fri Nov 12, 2004 4:59 pm
Posts: 3076
Location: Brazil
Well... if the PPU runs before the current CPU read, there's no more shaking/flickering in a few games. I wonder why...
It's irrelevant for CPU writes. About the sprite hit flag $2002:$40, is there any latency or is set immediately?


Top
 Profile  
 
 Post subject: Re: CPU timing precision
PostPosted: Mon Dec 28, 2015 4:41 pm 
Offline
User avatar

Joined: Mon Dec 29, 2014 1:46 pm
Posts: 753
Location: New York, NY
Zepper wrote:
Well... if the PPU runs before the current CPU read, there's no more shaking/flickering in a few games. I wonder why...
It's irrelevant for CPU writes. About the sprite hit flag $2002:$40, is there any latency or is set immediately?


Which games did it fix and which are still having issues?

The wiki does not mention any sprite 0 hit flag latency. Assuming that the sprite 0 hit is recorded in a latch (as opposed to somewhere in memory), it should be available by the next PPU cycle if not within the current PPU cycle.


Top
 Profile  
 
 Post subject: Re: CPU timing precision
PostPosted: Mon Dec 28, 2015 6:30 pm 
Offline

Joined: Sun Sep 19, 2004 11:12 pm
Posts: 19355
Location: NE Indiana, USA (NTSC)
I seem to remember there being a latency of about one or two dots (less than one CPU cycle) for sprite 0 hit. It's probably an artifact of the pixel pipeline.


Top
 Profile  
 
 Post subject: Re: CPU timing precision
PostPosted: Mon Dec 28, 2015 7:55 pm 
Offline
Formerly Fx3
User avatar

Joined: Fri Nov 12, 2004 4:59 pm
Posts: 3076
Location: Brazil
zeroone wrote:
Which games did it fix and which are still having issues?

Simpsons is one. ^_^;;


Top
 Profile  
 
 Post subject: Re: CPU timing precision
PostPosted: Mon Dec 28, 2015 9:22 pm 
Offline
User avatar

Joined: Mon Dec 29, 2014 1:46 pm
Posts: 753
Location: New York, NY
tepples wrote:
I seem to remember there being a latency of about one or two dots (less than one CPU cycle) for sprite 0 hit. It's probably an artifact of the pixel pipeline.


Someone really needs to document the PPU pixel pipeline and everything that is affected in detail. The wiki is absent of this information.


Top
 Profile  
 
 Post subject: Re: CPU timing precision
PostPosted: Tue Dec 29, 2015 6:57 am 
Offline
Formerly Fx3
User avatar

Joined: Fri Nov 12, 2004 4:59 pm
Posts: 3076
Location: Brazil
zeroone wrote:
tepples wrote:
I seem to remember there being a latency of about one or two dots (less than one CPU cycle) for sprite 0 hit. It's probably an artifact of the pixel pipeline.


Someone really needs to document the PPU pixel pipeline and everything that is affected in detail. The wiki is absent of this information.


Visual2C02 in JavaScript
http://www.qmtpro.com/~nes/chipimages/visual2c02/


Top
 Profile  
 
 Post subject: Re: CPU timing precision
PostPosted: Tue Dec 29, 2015 7:57 am 
Offline
User avatar

Joined: Mon Dec 29, 2014 1:46 pm
Posts: 753
Location: New York, NY
Zepper wrote:


Agreed. But, I have yet to figure out how to use it.

In a thread from a few months ago, we actually discussed this same topic. Delaying the sprite 0 hit by a tiny amount does fix The Simpsons. But, it seems to break some of Blargg's tests. Experiment and let us know what happens. If you post a new version of RockNES, I'd be happy to help you test some games.


Top
 Profile  
 
 Post subject: Re: CPU timing precision
PostPosted: Tue Dec 29, 2015 4:36 pm 
Offline
Formerly Fx3
User avatar

Joined: Fri Nov 12, 2004 4:59 pm
Posts: 3076
Location: Brazil
Actually, I need partners for development. This emulator was fully written by myself... and in the past, all my helpers "disappeared" without a trace.


Top
 Profile  
 
 Post subject: Re: CPU timing precision
PostPosted: Wed Dec 30, 2015 8:22 am 
Offline
User avatar

Joined: Mon Dec 29, 2014 1:46 pm
Posts: 753
Location: New York, NY
Zepper wrote:
Actually, I need partners for development. This emulator was fully written by myself... and in the past, all my helpers "disappeared" without a trace.


How did your prior helpers contribute to the project? Do you have a github link?


Top
 Profile  
 
 Post subject: Re: CPU timing precision
PostPosted: Wed Dec 30, 2015 1:03 pm 
Offline
Formerly Fx3
User avatar

Joined: Fri Nov 12, 2004 4:59 pm
Posts: 3076
Location: Brazil
Think in 1999. ;) No? Well, basically, I said "yes" to someone ready for help - it could be anyone that I would trust. I used e-mails and the ICQ messenger. ^_^;;


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 70 posts ]  Go to page Previous  1, 2, 3, 4, 5

All times are UTC - 7 hours


Who is online

Users browsing this forum: No registered users and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group