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VIDC Enhancer boards |
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Jeffrey Lee |
Message #121840, posted by Phlamethrower at 17:00, 29/1/2013, in reply to message #121838 |
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I assume you know that RISC OS 3 has a VDU variable for storing the VIDC clock speed? If your AutoVIDC module is able to set that then that would probably help compatibility with games, music players, etc. |
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Jon Abbott |
Message #121841, posted by sirbod at 18:51, 29/1/2013, in reply to message #121840 |
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Deja vu...I'm sure I asked if it was possible to set RISC OS VDU variables on Sun  |
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Jeffrey Lee |
Message #121842, posted by Phlamethrower at 18:59, 29/1/2013, in reply to message #121841 |
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Deja vu...I'm sure I asked if it was possible to set RISC OS VDU variables on Sun Quite possibly! I guess I should reply to that email... |
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Paul Vernon |
Message #121843, posted by PaulV at 21:53, 29/1/2013, in reply to message #121840 |
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So I'm reliably informed!
IIUC it writes to zero page at &1228 setting the current speed in kHz. I've not yet had the time to go through my PRM's to look for the right SWI call to set it though. I know OS_ReadVDUVariables 172 is used to read this info and is used for the purposes you mention.
In fact, now I'm writing this, I've just pulled the PRM's out and I can't find anything that remotely looks like what I'd expect to be like "OS_WriteVDUVariables"...
Paul |
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Jeffrey Lee |
Message #121844, posted by Phlamethrower at 22:51, 29/1/2013, in reply to message #121843 |
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In fact, now I'm writing this, I've just pulled the PRM's out and I can't find anything that remotely looks like what I'd expect to be like "OS_WriteVDUVariables"... Correct - you'd probably have to resort to poking the value directly.
Although one alternative (if you're creating your own VIDC lists for mode changes) is to specify it in one of the VIDC list type 1 extended parameters. I'd assume that all the OS does is write that value straight to the VDU var, but I haven't tried disassembling a RISC OS 3 ROM to check! |
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Paul Vernon |
Message #121845, posted by PaulV at 23:07, 29/1/2013, in reply to message #121843 |
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Just to follow up, it seems RISC OS writes the correct clock speed to this variable regardless of whether or not the hardware is capable of using the information.
I've just used the OS_ReadVduVariables to have a look at the clock speed and it's set correctly for every standard RISC OS mode that I've looked at.
Given that piece of info, it looks like I don't need to write the clock speed when setting the VIDC Enhancer state as it should be set when the MODE change occurs in the first place.
It does give me an idea though about automatically switching the Enhancer on/off for MODEs that are not defined in the AutoVIDC modules pre-defined MODE lists. Kind of like a "best guess" facility for custom defined modes that some games use.
Paul |
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Paul Vernon |
Message #121860, posted by PaulV at 22:04, 2/2/2013, in reply to message #120360 |
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You've prompted me to have a closer look @ my A420/1 motherboard: It's a flaky beast (some day I'll have the time to work out why) but in it's favour doesn't have the sync on green issue...
...I wonder if there's more than one revision of this motherboard / a previous owner fixed it and I just didn't notice / I've been lucky.
I think I'll go have a look now. It turns out this is documented in FCO2022. The Sync on Green signal was removed from later machines...
For the 400/1 series units with the serial numbers up to and including the following are affected.
410/1 : 27 AKB40 up to 1010000
420/1 : 27 AKB42 up to 1002700
: 25 AKB42 up to 1000380
: 25 AKB45 up to 1000017
440/1 : 27 AKB44 up to 1002300
440/1 LC : 25 AKB46 up to 1001600
It seems there's just under 17,000 400/1 and all of the A300, A400 and R140 series machines that have the Sync on Green issue.
Paul |
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Chris Evans |
Message #121863, posted by CJE at 11:30, 4/2/2013, in reply to message #121860 |
CJE Micros chap
Posts: 228
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For the 400/1 series units with the serial numbers up to and including the following are affected.
410/1 : 27 AKB40 up to 1010000
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Paul
Unfortunately it doesn't follow that 10000 were produced prior to the mod, as Acorn started serial no. at various numbers e.g. the first 27 AKB40 may have been 1002000 or 1009000
This is one of the reasons Acorn after a few years realised they didn't know how many ARM machines they'd sold!
[Edited by CJE at 11:31, 5/2/2013] |
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Peter Howkins |
Message #121864, posted by flibble at 13:46, 4/2/2013, in reply to message #121863 |
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For the 400/1 series units with the serial numbers up to and including the following are affected.
410/1 : 27 AKB40 up to 1010000
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Paul
Unfortunately it doesn't follow that 10000 were produced prior to the mod, as Acorn started serial no. at various numbers e.g. the first 27 AKB40 may have been 1002000 or 1009000
This one of the reasons Acorn after a few years realised they didn't know how many ARM machines they'd sold!
If people would like to find out, please contribute your serial numbers to this thread on StarDot.
http://www.stardot.org.uk/forums/viewtopic.php?f=42&t=4321
Statistical analysis, that improves which each serial number provided. |
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