Best Altirra settings to emulate a PAL atari?

[Mclaneinc]

Didn't add this to the Altirra thread as its both huge and mainly about bugs and suggestions.

 

Basically as the question from he topic, I've gone through the help file and chosen a few bits that suggest best emulation but would like to check what anyone thinks about or has suggestions about. I'm also hoping the thread could then help other users configure Altirra to the optimal level as close to hardware as possible, in this case PAL hardware.

 

Right, I'll list out the things I've set, I will only list the bits that are solely about hardware quality emulation rather than things like what disk drive mode, eye candy or optional addons etc.

 

Bicubic, says its best quality..It may deviate a little from TV / Monitor quality compared to real hardware (?) but I like a smoother picture.

 

Stretch to square pixels as it says its resembles PAL them most.

 

Overscan to Normal but also ticked extended extended pal for the first time as it says it supports software trickery, any demos that use it?

 

Unticked Fast Boot, not 100% sure what it does but I presume it bypass's some startup inits?

 

Ticked SIO override but sounds like its more for custom OS etc / custom hardware?

 

Now one I'm not sure of, I set latency as low as possible without cut outs to make the sound timing as close as possible but not sure what the extra buffer does or how it links into latency?

 

Also the Audio API, any pitfalls of which to choose? Set it to Dsound

 

Ticked non linear mixing as it says it matches hardware style.

 

CPU is set to stock 6502 and ticked enable illegal instructions, are there any non debugging options in there that need ticked?

 

 

That's it bar custom settings, have I missed anything?

 

Oh, is full screen preferential to Windowed, as I'm setting it to PAL (mostly) Vsync although ticked won't hit the Pal frequency as my LCD only has 60 - 75 as frequencies.

 

One thing I'd like in FS is what Winuae has, screen scaling, I used to play my Atari like many on a 14inch little Sony and then on a 8833 monitor so these large screen we have now just feel too big to me so I use it windowed to allow my personal choice but if FS has some better features it would be nice to be able to scale it as well.

 

That's just me tho, I'd imagine its a hell of a lot of work to add and that is something if is the case I'd not feel happy to request. (Avery is looking at the screen with two fingers like a gun saying "no chance sucker" )

 

All suggestions and help welcome, hopefully it could help others.

[Rybags]

Overscan shouldn't affect emulation, only how much of the generated display is actually shown.

 

I virtually never use fullscreen, I like to be able to use the debugger and/or quick switch between other applications. In theory the overscan mode might inadvertantly scale down the fullscreen size of the normal 40x24 area so maybe try that.

 

Sound - I'm not even sure if Altirra uses a different frequency base for PAL and NTSC - PAL sounds should be slightly lower frequency.

 

Stuff like SIO, illegal instructions etc aren't really a Pal/NTSC issue, more an overall emulation feature. IIRC, "Stop on BRK" is a default but real hardware doesn't act that way and you'd probably want it unchecked except for debugging situations.

[Mclaneinc]

Thanks for the answer Ry...

[phaeron]

Fast Boot bypasses the OS ROM checksum, disk boot requests to non-existent drives, and type 3 polling by DOS. It allows booting into BASIC or the DOS menu more quickly. However, in rare cases there can be compatibility issues with it on. Turn it off for the authentic Atari boot raspberry.

 

SIO override only matters if you are using a custom OS or emulated parallel bus (PBI) device that does something unusual with disk access requests. It's only needed if you expect disk access to not go to disk, like if you're using IDE firmware to map D1: to a disk image. It doesn't hurt to leave this on, as the worst that happens if it's not needed is you get one disk sector read on boot that's not accelerated.

 

Normal overscan should be fairly close to what can normally be seen. Extended overscan shows everything that can be displayed by sprites and playfield -- usually more than can be seen on TVs, but can be spotted with a capture card. Full goes beyond that to borders. The extra vertical space in Extended PAL mode is only usable with CPU-driven sprites, so you won't find it used except in a couple of demos.

 

Altirra automatically adjusts the aspect ratio when in PAL mode, so it's actually slightly more accurate to leave the display in that mode. However, the difference is very slight, about 3% IIRC, compared to the ~10% difference with NTSC.

 

DirectSound gives better (lower) audio latency, which means sounds and visuals match better. However, you'll get noise if the audio buffering is too low. If you've got the values as low as you can without the audio breaking up, that's good.

 

True 50Hz refresh rate for PAL is a pain in the butt on modern display hardware because monitors usually don't report support for refresh rates below 56Hz even if they do support it. Just trying to set a 50Hz display mode through the display driver won't work. This sucks, because the result is a quite obvious jitter every 5-6 frames. It can be worked around by overriding the EDID in the Registry, but it's annoying to do. This is often the only way to get a smooth PAL display, though. On a few laptops, it just happens that the "power saving" mode on the display lowers the refresh rate to 50Hz, which is ideal. I have been considering whether it would be possible to create a reasonably smooth PAL emulation on 60Hz displays through motion compensation, but I don't know if this can be done well enough to be usable.

 

One additional option you didn't mention: by default, Altirra runs at the actual rate of the Atari, which is 59.92Hz for NTSC or 49.86Hz for PAL. This is the most accurate but can give you slight jitters on the display occasionally. The Speed Options dialog can be used to speed up the emulation by 0.1-0.3% to eliminate this problem.

[Grevle]

What About using 100hz in the same way as Winuae emulator for Pal, Many monitors support 100hz (like mine) and Winuae can use 100HZ at least in some resolutions and get solid smooth sync to what appears to be Pal 50hz.

 

I dont know the mechanics behind that result but hasn,t it something to do with dividing the time step sync of 100hz in two and then get what appears to be 50hz ?, the C64 Emulator Micro64 also uses the same 100hz mode to get solid smooth Pal synced emulation. This mode may depend on the hardware ofcoarse, but i used this setting for Winuae And Micro64 and its works good.

 

The drawback seems to be not to be able to use 1920X1080 in 100hz but resolutions like 1024x768 or similar works for Winuae and Micro64 in 100hz.

Edited April 2, 2014 by GentleBaron

[Mclaneinc]

@Gentlebaron

 

Sadly most monitors these days unless you spend very heavily only support 60hz - 85hz., the old Dell Crt I had that died went from 50hz - 120hz, its was brilliant.

[Mclaneinc]

@Avery,

 

Thanks for the detailed run through, as said, hopefully others may benefit from the info.

 

And yes, forgot the actual speed of the machine

Edited April 2, 2014 by Mclaneinc

[phaeron]

Most emulators should be able to do PAL at 100Hz at least in windowed mode, since refresh rates vary anyway. Full-screen mode might be a bit more of an issue depending on how it's implemented, but at least in Altirra you can pick the refresh rate from all available full-screen modes in Options. However, it doesn't currently support frame-locked flicker modes.

 

120Hz capable LCD monitors have come down a lot -- they're below $300 USD at this point. The main downside the last time I looked at them was that they were universally all TN display panels that only went up to 1920x1080 and almost all were 6-bit. There was also a lot of variation in how well the panels actually updated at that high of a refresh rate. I opted instead for a 2560x1440, 30-bit display and don't actually have a display right now that's capable of >85Hz.