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Old 22 August 2013, 09:28   #1
ameath
 
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Floppy images & speed issues (Mac OS X)

Hello, I'm new to this forum and FS-UAE.

I spent some time working out how to to run Amiga games within self-contained MacOSX application bundles. All that is working well. My only issue now is with the speed at which some of the games run. My reference point is "Duck Tales", which seems to suffer from long wait times as it accesses the floppy disk images at key points in the game.

I have tried setting the floppy speed to 800 or to 0, for x8 speed or 'turbo' mode. Either way, the game is still loading very slowly from the floppies. For example, I will get a black screen and 'floppy access' occuring for about 15 to 20 seconds after the title screen and every time there is a change of scene. I have selected an Amiga 4000/040 as the emulated machine. It does not make any difference selecting a slower machine.

I have a fairly fast system for the purposes of emulation (Core i7, 16GB ram, 512mb Radeon HD card) and I never have any speed issues with emulators in general. I generally max all the speed settings out and never notice any lag associated with lack of processing power. In addition, I am running everything off an SSD drive, so theoretically disk access should be quite fast. I would have thought speed issues would manifest themselves in poor graphical/sound performance, rather than slow emulated disk access? I just want to run the games at the fastest possible speed without needing the nostalgia element of simulated floppy drives.

My first impressions are that this is either an artificial speed constraint designed to emulate the behavior of the original Amiga disk drives, or it is something to do with slowdowns in translating 68000 code to x86.

Can someone enlighten me? In theory, why can't the floppy access be effectively instanatenous like in DOSBox/Boxer? I realize Boxer does not have to translate 68k to x86 code and vice versa, but even when emulating 68k Macs in Basilisk the disk access itself is always fast.

Would I get any better performance running the games from hard drive images/folders?
 
Old 22 August 2013, 10:37   #2
ameath
 
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Is it because I am using IPF images and not ADF?
 
Old 22 August 2013, 15:04   #3
amigafreak68k
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For IPF images the speed should be at 100% not higher, because of some copy protections
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Old 22 August 2013, 16:25   #4
ameath
 
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I have just tried using ADF images rather than IPF, with floppy speed set to 0.

I certainly get much better performance. It's not instant, but where before I was waiting 25+ seconds it's now more like 5, which is much more acceptable.

Thanks.
 
Old 22 August 2013, 20:50   #5
Retro-Nerd
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Use the warp mode toggle key (or mapped to a pad button) instead of floppy speed. Works of course fine with all games in the FS-UAE database.
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Old 26 August 2013, 14:06   #6
ameath
 
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Wow, that's fast!

Actually, seeing how fast the 'warp' function blazes through everything… that seems to indicate that artificial constraints are being placed on emulation speed to make games playable on modern machines - otherwise they would run too fast?

Or is it doing something else, like skipping over certain processes? What is the reason that FS-UAE cannot have an option to adjust processor cycles like in DOSBox? Where possible, I am emulating an A4000, but in terms of disk loading it does not seem much faster than the A500.

I guess what I'm saying is, it would be nice to have a 'sweet spot' between warp mode and the speeds I am currently achieving.

This is what I include in my standard config in each application wrapper: (is there perhaps anything else I can add to speed things up?)

[config]
base_dir = $exe/../Resources
kickstart_file=a4000.rom
amiga_model=A4000/040
accuracy=1
texture_filter=nearest
fullscreen=1
fullscreen_height=1440
fullscreen_width=2560
floppy_drive_volume=0
floppy_drive_speed=0
floppy_drive_0=disk1.adf
floppy_drive_1=disk2.adf
 
Old 26 August 2013, 14:50   #7
TCD
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Quote:
Originally Posted by ameath View Post
Actually, seeing how fast the 'warp' function blazes through everything… that seems to indicate that artificial constraints are being placed on emulation speed to make games playable on modern machines - otherwise they would run too fast?
Yep, 'warp mode' basically just removes the waits for the next frame

Floppy speed should be the same in A500 and A4000 mode... and HD access too. Both are not CPU dependant, so I'm not sure why you'd expect to see a difference in access times.
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Old 26 August 2013, 22:33   #8
FrodeSolheim
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Quote:
Originally Posted by ameath View Post
Actually, seeing how fast the 'warp' function blazes through everything… that seems to indicate that artificial constraints are being placed on emulation speed to make games playable on modern machines - otherwise they would run too fast?

Or is it doing something else, like skipping over certain processes? What is the reason that FS-UAE cannot have an option to adjust processor cycles like in DOSBox? Where possible, I am emulating an A4000, but in terms of disk loading it does not seem much faster than the A500.
When using the A4000/040 model, FS-UAE runs in "fastest-possible-mode", which does adjust CPU cycles automatically. So one should not then expect to see much difference speed-wise in warp mode in a CPU-bound program at least. It is possible that fastest-possible mode isn't working optimally in FS-UAE. It is not an area I have prioritized, and I don't either have a good understanding of the fastest-possible code paths in UAE.

I don't recommend using A4000/040 for games though. You'll have much better compatibility with the 68000-based models, and of course, you can use A1200 for AGA support.

If the main goal is increasing the loading speed, you can use A500/500+/600/1200 and either use floppy_speed (but note that it may not be 100% compatible with all games), or toggle warp mode to skip through the loading parts, or use WHDLoad (with either memory-expanded A600 or A1200 model, depending on the game and WHDLoad slave).

Last edited by FrodeSolheim; 27 August 2013 at 09:56.
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Old 27 August 2013, 09:07   #9
Toni Wilen
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Fastest possible and warp mode are two totally different things.

Fastest possible: CPU runs as fast as possible (any idle time is used for CPU emulation), chipset and everything else runs normally.

Warp mode: Whole emulation runs as fast as possible but only from user point of view. Emulated program does not see any difference (exception: if fastest possible CPU is also enabled because CPU now runs _slower_ due to lack of idle time!)

Most games and demos run much faster in warp mode because most of them are synced to vblank. Only exception are programs that are CPU limited.
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