[Openmsx-bugs] [ openmsx-Bugs-897435 ] R800 is going too fast

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Bugs item #897435, was opened at 2004-02-15 14:23
Message generated for change (Comment added) made by m9710797
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Category: General/misc
Group: None
Status: Open
Resolution: None
Priority: 4
Private: No
Submitted By: Albert Beevendorp (bifimsx)
Assigned to: Wouter Vermaelen (m9710797)
Summary: R800 is going too fast

Initial Comment:
I was asked to check the cycle speed of the _MWP 
menu on MSX turbo R GT (_HIRO on MSX turbo R ST) 
between the yellow and the green color. The speed was 
verified with both the real machine and NLMSX where 
the frequency can be changed for both Z80 and R800.

The blink speed is too fast. It's about 4 times faster. 
When lowering the frequency to 7.16 MHz for the R800 
the blink speed is correct. Here's my suggestion:

Add R800 x-tal emulation which runs on 7.16 MHz. My 
guess the timer used for that blinking has its 
dependency on both actual x-tal frequencies.

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>Comment By: Wouter Vermaelen (m9710797)
Date: 2010-05-30 22:54

Message:
The extra cycles to access ROM or external RAM (comment of 2004-03-03) are
implemented (already some time ago).

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Comment By: Wouter Vermaelen (m9710797)
Date: 2010-05-30 22:47

Message:
Another test case: see 5th post of http://www.msx.org/forumtopic11165.html

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Comment By: Manuel Bilderbeek (manuelbi)
Date: 2005-01-18 21:10

Message:
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If you check out the animated flag parts in the Swiss demo,
you can see it still goes too fast for that: the flag moves
a lot slower on a real turboR GT with R800 mode.

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Comment By: Wouter Vermaelen (m9710797)
Date: 2004-03-03 20:31

Message:
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I did 4 things: 
 
 1) bugfix: the timing of some instructions was wrong 
 2) CAS/RAS optimization 
 3) refresh delay 
 4) extra delay for IO operations 
 
This is already good enough to make the BASIC test prog 
correct. The cycle speed in the menu is probably still a little too 
fast because the following things are not yet implemented: 
 
  1) 1 extra cycle to access ROM 
  2) 1 extra cycles to access external RAM  (not needed for menu) 
 

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Comment By: Albert Beevendorp (bifimsx)
Date: 2004-02-15 15:14

Message:
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I did some benchmarking with the following piece of Basic:

TIME=0:FORI=0TO9999:NEXTI:PRINTTIME

This gave the following results:

openMSX Z80: 1222
real thing Z80: 1224

openMSX R800: 129
real thing R800: 217

It shows the emulated R800 is running too fast.

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