VGA Only monitor driver

NovaCoder · 08 February 2009, 23:29

Hi,

Just out of interest, what does VGA only actually do? I realise it isn't a monitor driver in it's own right and it seem to make the multisync driver look a lot better on my CRT but I'm now sure how it works or what it does.

DDNI · 08 February 2009, 23:53

I think it cranks up the frequency a little to increase compatibilty with VGA screens

NovaCoder · 09 February 2009, 00:56

Quote:

Originally Posted by DDNI

I think it cranks up the frequency a little to increase compatibilty with VGA screens

Is it safe to use with all other drivers (eg HighGFX)?

NovaCoder · 22 April 2009, 02:58

After some more reading and rumors can I ask if using the 'VGA Only' driver increases the speed of the whole chipset or just the Lisa chip? I've been reading that it also increases the speed of AHI, how is that possible?

thomas · 22 April 2009, 09:33

VGAOnly is not a monitor driver. It is a patch which *slightly* changes the other drivers. It applies only to those drivers which already are VGA compatible (DblPAL, DblNTSC, Multiscan). Those drivers switch DMA into double speed. For audio (not only AHI) this means that samples can be played back at 56 kHz rather than 28kHz as with normal PAL or NTSC modes.

NovaCoder · 22 April 2009, 10:50

Quote:

Originally Posted by thomas

VGAOnly is not a monitor driver. It is a patch which *slightly* changes the other drivers. It applies only to those drivers which already are VGA compatible (DblPAL, DblNTSC, Multiscan). Those drivers switch DMA into double speed. For audio (not only AHI) this means that samples can be played back at 56 kHz rather than 28kHz as with normal PAL or NTSC modes.

Thanks Thomas.

So if it does switch DMA to double speed which as you say can increase the speed of other samples is it a good idea to always use it? Any side-effects or drawbacks from using it?

Thanks,
Chris

Toni Wilen · 22 April 2009, 11:08

There is no "double speed" mode. DMA is still as fast (or slow) as previously.

Audio supports higher sample rates only because doublescan modes have halved horizontal scanline time (instead of standard 227 DMA slots, there is only about 120 slots or so, depends on mode) and all DMA in Amiga (except copper and blitter) is synced to scanlines, audio for example is 2 8-bit samples per channel per scanline. (same sample pair is repeated if rate is larger than DMA handle)

NovaCoder · 22 April 2009, 12:35

Hi Toni,

So if your running in a doublescan mode (eg DBLPAL) you get no additional 'benefit' from also sticking the 'VGA Only' monitor driver in your DEVS/Monitors folder?

Which ones are the doublescan modes? What about something like HighGFX?

Brakus · 22 April 2009, 15:29

Quote:

Originally Posted by NovaCoder

Is it safe to use with all other drivers (eg HighGFX)?

I had left it in inadvertedly and was having weird screen issues with DpaintIII and Sysinfo on my 1200 equipped with Indivision... Removed it and all was normal again...

The screens in both apps were shifted to the right...

08 February 2009, 23:29	#1
NovaCoder Registered User Join Date: Sep 2007 Location: Melbourne/Australia Posts: 4,400	VGA Only monitor driver Hi, Just out of interest, what does VGA only actually do? I realise it isn't a monitor driver in it's own right and it seem to make the multisync driver look a lot better on my CRT but I'm now sure how it works or what it does.

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08 February 2009, 23:53	#2
DDNI Targ Explorer Join Date: Mar 2006 Location: Northern Ireland Posts: 5,431	I think it cranks up the frequency a little to increase compatibilty with VGA screens

22 April 2009, 02:58	#4
NovaCoder Registered User Join Date: Sep 2007 Location: Melbourne/Australia Posts: 4,400	After some more reading and rumors can I ask if using the 'VGA Only' driver increases the speed of the whole chipset or just the Lisa chip? I've been reading that it also increases the speed of AHI, how is that possible?

22 April 2009, 09:33	#5
thomas Registered User Join Date: Jan 2002 Location: Germany Posts: 6,985	VGAOnly is not a monitor driver. It is a patch which slightly changes the other drivers. It applies only to those drivers which already are VGA compatible (DblPAL, DblNTSC, Multiscan). Those drivers switch DMA into double speed. For audio (not only AHI) this means that samples can be played back at 56 kHz rather than 28kHz as with normal PAL or NTSC modes.

22 April 2009, 11:08	#7
Toni Wilen WinUAE developer Join Date: Aug 2001 Location: Hämeenlinna/Finland Age: 49 Posts: 26,502	There is no "double speed" mode. DMA is still as fast (or slow) as previously. Audio supports higher sample rates only because doublescan modes have halved horizontal scanline time (instead of standard 227 DMA slots, there is only about 120 slots or so, depends on mode) and all DMA in Amiga (except copper and blitter) is synced to scanlines, audio for example is 2 8-bit samples per channel per scanline. (same sample pair is repeated if rate is larger than DMA handle)

22 April 2009, 12:35	#8
NovaCoder Registered User Join Date: Sep 2007 Location: Melbourne/Australia Posts: 4,400	Hi Toni, So if your running in a doublescan mode (eg DBLPAL) you get no additional 'benefit' from also sticking the 'VGA Only' monitor driver in your DEVS/Monitors folder? Which ones are the doublescan modes? What about something like HighGFX?

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