Game Glitches on MegaAGS

[Malor]

Is there any difference between this Kickstart environment and having an appropriate Kickstart rom installed on your system (maybe a 1.3-3.1 switcher)? I'm talking about real Amiga hardware.

It is different. If you have the correct Kickstart and hardware for a given game, you can just run it directly.

I'm unclear on the exact technical details of how it works, so this is speculation: I believe WHDLoad instead loads a new Kickstart at a different address, and then just before launching, changes a basic pointer-to-Kickstart in low memory. IIUC, all Kickstart calls are supposed to index through base pointer plus offset, so using a different Kickstart means loading it into RAM and changing that pointer. It's not real virtualization, but well behaved programs should work with it.

If it was 68030-and-up, WHDLoad could be using the MMU to provide a true virtual address space, but since the program works on even a basic 68000, I think it *has* to be using that pointer approach. I don't actually know this to be a fact, however: the entire paragraph above is guesswork based on what I know about the 68K family, and the knowledge that Kickstart can be relocated by programs like PrepareEmul, which is used for Macintosh emulation. (the Mac demands the use of memory where Kickstart normally is, so it has to be moved before Mac programs can launch.)

When WHDload exits, on the 68010 or higher, it can restore the Kickstart pointer before resuming execution of the host Workbench. I have always understood that exiting didn't work correctly on the 68000, and that a reboot was the only option, but I'm being contradicted above, so that might be wrong.

Again: lots of guesswork here on technical internals, based on program behavior and hardware capabilities. If anyone claims to have actual knowledge, trust them more than me.

[limi]

I have glitches on Shadow of the Beast on MegaAgs on Mister, but not on Mist and other FPGAs and not on real A1200 neither

You have to be way more specific if this is going to be useful — and for the record, I can’t see any issues with the current version of Shadow of the Beast in WHDLoad, but I also don’t play that game ever, so maybe I’m missing some detail.

Useful to narrow down what you are describing, so we can take a look:

• Where exactly are the glitches?
• Are you using WHDLoad on the other FPGA cores?
• Are you using WHDLoad on the A1200?
• Are you using the supplied settings unmodified? (e.g. Did you make sure D-Cache is off etc?)

“I have glitches” is impossible to troubleshoot in a meaningful way

[Bren McGuire]

Yes, it’s still “virtualized” (I know, it’s not like it has hypervisors or anything, but it’s as close as you get), a hardware switch for Kickstart ROMs would be different.

Would it be better?

In any case, as Optiroc already stated — the best way to get close to 100% identical behavior is to use the various CPU, Kickstart and ADF settings, but for a large number of games WHDLoad will be acceptably close. Of course, we should still file bugs and see if they can be fixed, but it does depend on the circumstances; sometimes it will be very hard to patch the original binary to work well on hardware it was not originally written for. It’s kind of a miracle that it works as well as it does, a lot of WHDL developers have put in a lot of clever work to make it be as good as it is.

Speaking of that, while on the Mega AGS menu I selected 68000 as a CPU, then I launched a game but it was glitched anyways, why is that?

Now, this may be a dumb question (but I'm gonna ask it anyways). Should you mount a 68000 and a 68020 with a switcher, and also a kickstart switcher on a real Amiga 1200, would it be 100% compatible with all games? Not that I've any intention to do it, it's just a theoretical curiosity.

[limi]

Speaking of that, while on the Mega AGS menu I selected 68000 as a CPU, then I launched a game but it was glitched anyways, why is that?

MegaAGS generally requires 68020 and AGA. Some things may work with 68000, but it’s not a supported configuration. If you want 68000, use ADFs and Kickstart 1.2 or 1.3. (2.0 will work too, but breaks many games). Use the included configuration for MegaAGS.

Now, this may be a dumb question (but I'm gonna ask it anyways). Should you mount a 68000 and a 68020 with a switcher, and also a kickstart switcher on a real Amiga 1200, would it be 100% compatible with all games? Not that I've any intention to do it, it's just a theoretical curiosity.

No. You can’t run a 68000 in an Amiga 1200. One is a 16-bit processor (with some 32-bit functionality), and the other one is a 32-bit processor.

[Bren McGuire]

MegaAGS generally requires 68020 and AGA. Some things may work with 68000, but it’s not a supported configuration. If you want 68000, use ADFs and Kickstart 1.2 or 1.3. (2.0 will work too, but breaks many games). Use the included configuration for MegaAGS.

That's what I did, but then I changed to 68000 on the fly, right before loading a game from the list. So, either MiSTer doesn't change settings in real time or there's some other reason why it didn't work.

[Optiroc]

MegaAGS generally requires 68020 and AGA. Some things may work with 68000, but it’s not a supported configuration. If you want 68000, use ADFs and Kickstart 1.2 or 1.3. (2.0 will work too, but breaks many games). Use the included configuration for MegaAGS.

That's what I did, but then I changed to 68000 on the fly, right before loading a game from the list. So, either MiSTer doesn't change settings in real time or there's some other reason why it didn't work.

CPU type is applied on reset now, iirc. I seem to remember that it was applied immediately at one point, which can practically only lead to an instant crash.

[lroby74]

• Where exactly are the glitches?
  Only and once when you start playing the game, horizontal rows on parallax background, and when you run for going after the water well, it gets worse because appaer bad blocks graphic on main character (player)
• Are you using WHDLoad on the other FPGA cores?
  I am using WHDLOAD SoB game from MegaAGS taken from archive.org on an AGA+020 configuration with 2 mb chip ram and 384 mb fast ram (it does same with 8 mb fast ram)
• Are you using WHDLoad on the A1200?
  Same file MegaAGS flashed on CF
• Are you using the supplied settings unmodified? (e.g. Did you make sure D-Cache is off etc?)
  Yes, and strange thing is my friend has same glitches on his Mister)

[Malor]

Yes, it’s still “virtualized” (I know, it’s not like it has hypervisors or anything, but it’s as close as you get), a hardware switch for Kickstart ROMs would be different.

Would it be better?

In any case, as Optiroc already stated — the best way to get close to 100% identical behavior is to use the various CPU, Kickstart and ADF settings, but for a large number of games WHDLoad will be acceptably close. Of course, we should still file bugs and see if they can be fixed, but it does depend on the circumstances; sometimes it will be very hard to patch the original binary to work well on hardware it was not originally written for. It’s kind of a miracle that it works as well as it does, a lot of WHDL developers have put in a lot of clever work to make it be as good as it is.

Speaking of that, while on the Mega AGS menu I selected 68000 as a CPU, then I launched a game but it was glitched anyways, why is that?

Now, this may be a dumb question (but I'm gonna ask it anyways). Should you mount a 68000 and a 68020 with a switcher, and also a kickstart switcher on a real Amiga 1200, would it be 100% compatible with all games? Not that I've any intention to do it, it's just a theoretical curiosity.

Kickstart switchers were definitely a thing, and you could expand 68000-based Amigas to have an 020 or higher, typically plugged into the CPU socket, aka a daughterboard. Some would allow you to move the original 68000 to an empty socket on that board, while also providing a 32-bit CPU and usually local 32-bit RAM. All other I/O and expansions had to run through the 68000 motherboard socket, which meant they were limited to 16-bit access and slow clocking. It was the fast RAM on the daughterboard that let that type of expander work well; the 020 or 030 could run at full speed on daughterboard RAM, and was only slow when accessing chip RAM.

The main downside here is that you were stuck with the original chipset, and all I/O was much slower than it would be on a native 32-bit system. I have a vague idea that maybe some of the 030 expanders came with onboard SCSI to accelerate drive I/O, but I never owned one, so I'm not certain.

If you wanted access to the AGA chipset, you were stuck with an 020 or higher, because those systems were 32-bit. The 68000 can't plug into those boards because it doesn't have enough address and data pins. If you wanted to run old games on an AGA machine, WHDLoad was pretty much the only option.

With all the glitches you're talking about, I'm wondering if maybe you didn't install the configuration files and the monitor settings in the right spots. Maybe try going back over the MegaAGS instructions extremely carefully, and make sure you take every required step? I played some Shadow of the Beast here, a week or so ago, and it seemed perfect to me. I'm not real fond of the game, but I played for fifteen or twenty minutes and didn't see any issues at all.

edit: also, Minimig is prone to overheating on a naked Mister. You'll want a heatsink on the FPGA and an active fan for stable results.

[limi]

That's what I did, but then I changed to 68000 on the fly, right before loading a game from the list. So, either MiSTer doesn't change settings in real time or there's some other reason why it didn't work.

That’s… not how computers work.

That’s like (yes, slight exaggeration to make my point) expecting the 16-bit SNES version of Castlevania to continue playing as the 32-bit PlayStation version to just be able to upgrade/downgrade the CPU and graphics processors on-the-fly. These are two very different computers, you can’t just replace core parts of them with a switcher and expect them to work. One is a computer from 1985, the other a computer from 1992. Just because it is possible to do that in the MiSTer menu, doesn’t mean it will work.

[limi]

edit: also, Minimig is prone to overheating on a naked Mister. You'll want a heatsink on the FPGA and an active fan for stable results.

As a known hater of fans (because, why would you want fan noise with your retro gaming), I can tell you that this is absolutely not true. I have used my MiSTer Amiga core without a fan for years, I keep it on 24/7 since it’s a 6-8W device. I have never had issues with heat. And I use this device with the Amiga core a lot, for obvious reasons.

If you put it in a completely enclosed case that isn’t passively cooled like the MisterAddons aluminium one, maybe it’s possible to achieve sufficient heat build-up to make it an issue. But the DE-10 nano is drawing as much power as a (old-style, before fast charging) phone charger, so it’s not an issue at all. If you use your MiSTer without a case or with one of the open PCB or acrylic cases — or the aforementioned passively cooled aluminium case — you are fine.

The DE-10 nano is industrial hardware that is rated for over a million hours operating at 100°C — which it never reaches. It will be fine. If it was prone to overheating, do you really think Terasic/Intel would have shipped it without a fan?

(If you do core development in HDL and may have a bug that triggers some excessive heat, I’m sure it’s theoretically possible. But that’s not most users.)

[Malor]

I think you're just lucky. My Minimig is unstable without a fan. It usually won't even boot.

[limi]

Wow. All of my friends run Minimig and the MiSTer without fans (on my recommendation), and they have no issues. That’s the first I’ve heard of that happening (but obviously it’s real for you). Even the most demanding cores (like ao486) have no issues for us. Maybe you got unlucky instead of us getting lucky?

(also, one caveat I didn’t mention is of course if you live in an extremely hot climate, I don’t have any experience with that in the balmy California weather, ~20-30°C)

Is any case, I don’t think that’s what’s going on with Bren’s issues — if his core didn’t boot, that would be very different.

[Malor]

It is extremely hot here, but I have air conditioning, so the Mister doesn't know.

I dunno whether you're lucky or I'm unlucky, but mine's flaky without a fan, and the general setup instructions for the Mister explicitly say that a fan is recommended for Minimig and AO486. I don't think this is an unusual issue.

Plus, if you use a nice Noctua 40x10mm fan, you're not even going to hear it, unless it's set up within like a foot of your ear. They're wonderfully quiet, albeit expensive. (~$20.)

edit to add: you also, of course, want a 22mm heatsink.

[Bren McGuire]

If you wanted access to the AGA chipset, you were stuck with an 020 or higher, because those systems were 32-bit. The 68000 can't plug into those boards because it doesn't have enough address and data pins. If you wanted to run old games on an AGA machine, WHDLoad was pretty much the only option.

Thanks for the detailed explanation, I was under the impression that the A1200 was the definitive Amiga "home" machine but I was wrong, it seem that an A600 with a kickstart switcher is much more compatible (except for the AGA games, of course), especially considering that the A600 has the same internal hard drive and memory options of an A1200. Speaking of which, will WHDLoad games be glitch free on an A600 with the appropriate kickstart mounted?

With all the glitches you're talking about, I'm wondering if maybe you didn't install the configuration files and the monitor settings in the right spots. Maybe try going back over the MegaAGS instructions extremely carefully, and make sure you take every required step? I played some Shadow of the Beast here, a week or so ago, and it seemed perfect to me. I'm not real fond of the game, but I played for fifteen or twenty minutes and didn't see any issues at all.

edit: also, Minimig is prone to overheating on a naked Mister. You'll want a heatsink on the FPGA and an active fan for stable results.

I'm not the Shadow of the Beast guy (in fact I played it for a while and I found nothing wrong), all the glitches I reported were confirmed by others.

[limi]

Thanks for the detailed explanation, I was under the impression that the A1200 was the definitive Amiga "home" machine but I was wrong, it seem that an A600 with a kickstart switcher is much more compatible (except for the AGA games, of course), especially considering that the A600 has the same internal hard drive and memory options of an A1200. Speaking of which, will WHDLoad games be glitch free on an A600 with the appropriate kickstart mounted?

WHDLoad will never be completely “glitch free”. It’s doing something to the games that they were never meant to do, without the source code for those games.

The ultimate in compatibility (if you don’t care about AGA) would be an Amiga 500 with a memory expansion and floppies, or a Gotek drive. Plenty of games will break on the Amiga 600 too, not all games can handle the different chip RAM setup — heck, some games on the Amiga 500 required you to remove the memory expansion. There is no “one true setup”, since there was no “one Amiga”.

It’s a trade-off between convenience and compatibility, just like MiSTer itself is. Are there some glitches in some games? Yes. Do I play way more games on the MiSTer than on my original Amiga setup? Heck, yes.

[Bren McGuire]

Plenty of games will break on the Amiga 600 too, not all games can handle the different chip RAM setup — heck, some games on the Amiga 500 required you to remove the memory expansion. There is no “one true setup”, since there was no “one Amiga”.

That's unfortunate. I'll have to give up on that.

It’s a trade-off between convenience and compatibility, just like MiSTer itself is. Are there some glitches in some games? Yes. Do I play way more games on the MiSTer than on my original Amiga setup? Heck, yes.

Me too, I hope one day we could also play CD32 games natively.

[Malor]

Yeah, as Limi is saying, there is no perfect Amiga that covers everything. There were just too many changes in the system over time. Well-behaved apps and games stayed very compatible through all the generations (the Shanghai tile-clicking game, for instance, ran perfectly on every Amiga model), but there were substantial numbers of games that broke the rules. Some titles, for instance, used the upper byte on pointers to store data, because on the 68000, that byte was ignored. (MacOS also did this in early versions.) Try to run that code on a 68020, where that byte is used, and the resulting crash was likely to be spectacular. There were also plenty of titles that depended on how a given Kickstart behaved, and when that behavior changed even a little (eg. upgrading to Kickstart 2.0 from 1.3), they blew up. And then there were titles that shut the OS down and took over completely... oddly, those tended to stay pretty compatible.

WHDLoad and its recipes are kind of a middle-of-the-road compromise. It's particularly useful on later-model Amigas with 020s and higher. Most of the recipes were made by hobbyists that were patching compiled binaries, without source code, and there can definitely be issues. But, by and large, most games work fine. I'd characterize it as a 95% solution, and the outliers that don't work are usually not that great anyway.

[akeley]

It's not really that big a deal, because most WHDL games are ok, at least most of the big multi disk ones, and we can change configs on the fly. Just keep a floppy collection handy (Gamebase recommended atm). With turbo drive enabled playing 1/2 disk games from adfs is just fine.

The only real annoyance are more niche WHDL games which might have game-breaking bugs hidden later on. I've found this out the hard way when trying to play Starflight and seeing that the protection hasn't really been removed - after +10 hours of gameplay.

[Malor]

You might check to see if there are other WHDLoad recipes for that game. Pre-Mister and pre-MegaAGS, I built a couple of new images from IPF originals, on WinUAE, to work around problems in a downloaded version.

In my experience, IPF originals tend to be the best quality, so working from those is most likely to generate a correct image. This means you'll probably have to build them on WinUAE and then import them to the Mister. Remember that building images takes lots of RAM, so allocating 32MB or more with WinUAE is a good idea.

[limi]

You might check to see if there are other WHDLoad recipes for that game. Pre-Mister and pre-MegaAGS, I built a couple of new images from IPF originals, on WinUAE, to work around problems in a downloaded version.

We are pretty diligent about making sure we always include the latest WHDL recipes with every release, but if someone managed to find a better way to build a given game, we will certainly update our scripts.

[Sagat]

Where exactly are the glitches?
game: Dogs of war, using the MegaAGS version. it's a tricky one though. First run the game is fine, get a high score play again, there is a control issue. your character just keeps on turning. (could try and make a vid if that helps)

Are you using WHDLoad on the other FPGA cores?
whd load as the program only for amiga core, i do use vhd for sharp and msx as well.

Are you using WHDLoad on the A1200?
don't have a actual 1200. Mister is set up as AGA

Are you using the supplied settings unmodified? (e.g. Did you make sure D-Cache is off etc?)
d-chace is indeed off, i do no recall playing with settings but i did set it up ages ago

i also didn't see this bug mention on
http://mantis.whdload.de/view_all_bug_page.php

[limi]

i also didn't see this bug mention on
http://mantis.whdload.de/view_all_bug_page.php

I would file it there, then. Unlikely to be anything related to Minimig core or MegaAGS when it’s that specific to that game. :)

(Great game for two players, by the way!)

[Sagat]

It's a oddly specific one. Because i had it several times (spread over 2 days, and even after running an update all) and then decided to play around a bit with my 'build' and when buying other weapons it doesn't seem to trigger. But when buying a bazooka (the green/russian one) and a few shots, grenades and then a specific gun (sa50, if you've played the game it's the geen the one near the hand guns but with more range than both ak47/m16) and buying ammo......IN THAT ORDER. That seems to trigger it. But only when playing the game again after game over (not sure if high score entry is a requirement).

So most likely a game bug, altho with this being my fave starter weapon i should have encountered it a lot when i played it back in the day on my real miga. Altho i was better at the game then so would most likely complete it or just play something else on game over. Also knew where to start to buy a more long range gun and the exact amount of bazooka shot and nades to complete mission one, afterwards money wouldn't be an issue, so i guess i would not have bought that gun a lot :S

(and yes, def great fun with 2 players, whenever a lesson would not push through me and a mate would just quickly go over to my house and play it ) I do recall (from back in the day) there was an issue/bug where sometimes you couldn't purchase grenades or ammo and would need to buy a gun first, did encounter that one a bit as well, ah nostalgia

[limi]

Yeah, the game certainly has a fair share of bugs. If you are capable of playing it on another “platform”, e.g. from ADF disks on the MiSTer or disk/WHDLoad on an Amiga emulator like WinUAE, you can probably narrow it down to whether it’s a game bug, a MiSTer bug, or a WHDLoad bug. That’s a fair bit of work, of course.

[Sagat]

Yeah, the game certainly has a fair share of bugs. If you are capable of playing it on another “platform”, e.g. from ADF disks on the MiSTer or disk/WHDLoad on an Amiga emulator like WinUAE, you can probably narrow it down to whether it’s a game bug, a MiSTer bug, or a WHDLoad bug. That’s a fair bit of work, of course.

i think i still have win uae installed on my pc. Could def give it ago, but have to be honest, i completed the game again yesterday so the urge to to play is low. Still curious about the bug though.

Especially in the light of the creators of the cores, now THAT is work. (and very much appreciated ) a quick play test is not.

[Sagat]

And to finish up, got win uae running, but with an ipf version of DOW. Could not reproduce the bug. Turns out mister amiga does not support ipf, or at least not 'out of the box' so unable to verify if the issue is solved on mister as well. But even as is, safe to say that version of the game most likely played some part, again with me also having no memory of this happening back with my 'real' amiga back in the day. Thanks!

[fierman]

I have had numerous glitches with a lot of games in the WHDLoad collection on my Amiga1200. Dogs of War is one of them. It's just the way it is, there are so many hardware combinations possible, you are bound to strike a condition triggering a bug or glitch all the time.

[Malor]

Minimig is quite good, but it does seem to be less compatible than WinUAE. As we were talking about in another thread, the fact that it supports only ADF images may be related; either the original crack might be bad, or the WHDLoad recipe might have errors. Running direct from IPF bypasses both those potential bug sources, but isn't currently possible on Minimig. There was some argument about whether there's even an open-source IPF implemention that the Minimig core could use.

IPF might someday happen, but it could be a long while.

[Sagat]

I have had numerous glitches with a lot of games in the WHDLoad collection on my Amiga1200. Dogs of War is one of them. It's just the way it is, there are so many hardware combinations possible, you are bound to strike a condition triggering a bug or glitch all the time.

Welp should add that it is definitely not my most used core so milage may vary but.
I def didn't experience many bugs!
I love swos still (really which real gamer doesn't ) and that occasionally has a gfx issue, a single line visible on the pitch.
Lotus espirit feels off to my memory. the start seems sluggish? when the race gets going it does feel fine. Ofc it could be the mind playing tricks. I love outrun on megadrive even with it's limitations and if i then play lotus it feels amazing!

But apart from these most stuff i replayed feel quite good and accurate to how i recall it on my amiga 500!
This is why the dog of war thing stood out so much. Still very interesting reads. And yeah as i generally use my mister mainly for non home computer cores, i do not have a mouse attached. Playing on an emulator on pc that is very different and as someone who tends to hop a lot between games, that is a pro.

[Optiroc]

I have glitches on Shadow of the Beast on MegaAgs on Mister, but not on Mist and other FPGAs and not on real A1200 neither

The glitches in Shadow of the Beast come and go, it seems. It used to work without flaws.