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#112416 - 01/31/18 05:43 PM A bug in i8275 emulation  
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fulivi Offline
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The moment I saw the log message on commit f652d21e16 "i8275: handle invisible field attributes and "end of row - stop dma" special code better...." I knew it was going to break video emulation on hp64k..
And indeed, video stays black now.. no sign of life.
Should I report the bug somewhere else besides here, please?
Thanks.
--F.Ulivi

#112417 - 01/31/18 06:15 PM Re: A bug in i8275 emulation [Re: fulivi]  
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Originally Posted by fulivi
The moment I saw the log message on commit f652d21e16 "i8275: handle invisible field attributes and "end of row - stop dma" special code better...." I knew it was going to break video emulation on hp64k..
And indeed, video stays black now.. no sign of life.
Should I report the bug somewhere else besides here, please?
Thanks.
--F.Ulivi


I've posted an issue I found earlier in testing to the GitHub commit . It basically hard locks the emulation nearly 10 seconds in as I've noted.
https://github.com/mamedev/mame/commit/f652d21e167265bded620fab397f142d18bd7b45

There may be other sets with regressions - those are the only ones I was able to determine via snapshot/watchdog checking.




#112420 - 01/31/18 07:44 PM Re: A bug in i8275 emulation [Re: fulivi]  
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Oops. attotime::zero is not the same as attotime::never apparently smile Testing the fix.

#112421 - 01/31/18 08:09 PM Re: A bug in i8275 emulation [Re: fulivi]  
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attotime::never is the opposite of attotime::zero, never = the largest possible attotime (which would be like years in the future, but the code generally all treats it specially so it never happens).

Set a timer to zero and it fires immediately. Set it to never and it never fires.

#112426 - 01/31/18 10:25 PM Re: A bug in i8275 emulation [Re: fulivi]  
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This diff fixes hp64k and breaks only one other driver (tim100). I've not tested rt1715 and sm1800, which are 'not working'.

Code
@@ -516,7 +517,7 @@ WRITE8_MEMBER( i8275_device::write )
                        LOG("I8275 IRQ 0\n");
                        m_write_irq(CLEAR_LINE);
                        m_write_drq(0);
-                       m_drq_on_timer->adjust(attotime::zero);
+                       m_drq_on_timer->adjust(attotime::never);
 
                        m_param_idx = REG_SCN1;
                        m_param_end = REG_SCN4;

#112428 - 02/01/18 03:04 AM Re: A bug in i8275 emulation [Re: fulivi]  
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Robbbert Offline
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sm1800 currently shows a grey screen with a blinking black cursor in the home position.


tim100 is now causing MAME to freeze, which is unacceptable. Please fix that.

#112446 - 02/01/18 09:49 PM Re: A bug in i8275 emulation [Re: fulivi]  
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rt1715 and sm1800 (and ipds) don't actually hook up the 8275 to DMAC (no MCFG_I8275_DRQ_CALLBACK defined) so nothing should change for them either way.

tim100 is a puzzle so far.

#112616 - 02/14/18 06:31 PM Re: A bug in i8275 emulation [Re: fulivi]  
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https://github.com/mamedev/mame/commit/a2ad15beef865aa22f5b77e3d2e83f3b95b91f17 restores visuals in hp64k and doesn't break tim100 & others in the process (at least not in first 10 seconds of run time). I could not test trs80dt1, though.

#112829 - 03/10/18 03:04 PM Re: A bug in i8275 emulation [Re: fulivi]  
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AJR Offline
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ms6102 now piles endless amounts of garbage text on the screen. I had hoped that that driver would at least be half-working, which it wasn't really even before the recent 8275 changes, since this Soviet terminal clones at least the VT100 keyboard interface circuit.

#112831 - 03/10/18 03:37 PM Re: A bug in i8275 emulation [Re: fulivi]  
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ms6102 is a mystery -- every other char in video memory is a field attribute code. Maybe the other 8275 is reading them while the first one is not looking...

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