Amiga questions you've always been too embarrassed to ask

[dJOS]

I was wondering if any of the a500 expansions eg GVP series could replace the a500 power supply via the expansion connector?

[roy bates]

Originally Posted by dJOS

I was wondering if any of the a500 expansions eg GVP series could replace the a500 power supply via the expansion connector?

i actually thought about that some years ago and came to the conclusion it would be a definite no,because of the missing power rails that were missing.

but works the other way around amiga to power the expansion via the amiga.

[slaapliedje]

Originally Posted by ajk

The 2 megs of chip RAM is enough for "normal" video screenmodes, especially with FBlit (if you aren't using it already, get it!) etc., and power users always had the option of a separate RTG board which blows AGA out of the water anyway.

I'm not sure what exactly is needed to add support for more chip RAM, but it would require the redesign of probably several of the custom chips. Clearly this has been too much of a challenge so far. Perhaps one day we can stick WinUAE on an FPGA and have that updated chipset

I have RTG, but occasionally it's more convenient (when switching through games with WHDLoad) to be using an AGA resolution, and after loading up the Amikit for Real desktop I have about 150KB of memory left at 640x512x256. You have to lower it to 64 colors to be able to do much of anything. Granted I could strip some of the excess stuff out of it, but then it's no longer Amikit. But that's really the reasoning behind wanting even just 2mb more.

I also think it'd be nice for performance to somehow just bypass the 2mb chip mem and use all fast mem, but I realize that's probably extremely unfeasible.

slaapliedje

[ajk]

@slaapliedje

I've got an RTG+Indivision combo in my A4000 too. With automatic monitor switching, running WHDLoad games from the RTG Workbench works fine.

But when I do boot to a plain WB3.1 install, I use something like 1024x384 at 4 or 8 colours. This is, relatively speaking, blazing fast, and with FBlit installed, practically all of the chip memory remains free. Haven't got a screenshot of the A4000 right now, but here is an image of my A600 with a similar setup. I wouldn't even attempt to stuff a native-mode Workbench full of eye candy, it just always gets too slow (even with extra chip memory, as you mentioned).

[dJOS]

Originally Posted by roy bates

i actually thought about that some years ago and came to the conclusion it would be a definite no,because of the missing power rails that were missing.

but works the other way around amiga to power the expansion via the amiga.

That's what i thought too but I was talking to Andrew the creator of the original Phoenix 1000 board on Monday night at Adelaide Amiga User Group meeting and he was showing us an a500 expansion chassis he had developed back in the day.

It basically went underneath the a500 and contained a ram expansion board, 40mb miniscribe hard drive (XT I think) and power supply. He was adamant that it powered the a500 too but I was sceptical - needless to say I was proved right when the a500 we plugged in didn't work without its own power brick.

[Jope]

Originally Posted by lifeschool

First question: In the outrun cabinet there was a scaler chip. Would a scaler chip inside the amiga have helped with display modes and sprite handling. I know the Amiga was a general machine, not built with games in mind, but would a 3rd party trapdoor add-on really make the machine 'arcade compatable'?

A scaler chip would have helped to run sprite scaling games such as Out Run, Space Harrier, etc.

A 3rd party addon would have required people to buy that addon to play the games. Perhaps one would have been successful, but most likely not.

Are we supposed to read arcade compatible literally? No, it wouldn't make it compatible, but it would ease porting of games that rely on that technology.

Second question: On a very fast AGA machine, is it possible to run mame, or software to emulate the scaler chip?, and have outrun running in 16 colours or whatever?

This hypothetical AGA machine would require a CPU card that is faster than any of the cards in existence. But if you had this unobtainable CPU card with enough horsepower to render it all in software and then just dump the frames to chip RAM, yes probably.

Third Question: As some arcades had 000 processors, surely it was possible to port the code directly and work around the custom chips and dma registers with a softare VM. Ok this may be very hard in reality, but is it possible?

Possible, yes, playable framerates, no. Porting something and running it in a VM are not the same thing. The VM approach would be very very slow indeed, but naturally it is possible to do - just not a good idea.

But be it port or VM, many of those arcade machines had specialized hardware that was not present in the Amiga, thus the ported code or VM hypervisor would have to do that hardware's job in software -> slower game.

[Mrs Beanbag]

It's a real shame the Blitter's functionality was not augmented for AGA, it was a hair's breadth away from being usable to do sprite scaling/rotation. In fact some demos use it to do exactly that but it takes some effort and isn't very convenient. If only the line drawing function could use all DMA sources it would have been far more useful for this sort of thing.

[slaapliedje]

The Atari Lynx (also worked on by the developers of the Amiga) had hardware scaling in it. You could see it easily in Gauntlet; The Third Encounter, when the characters would sort of fall into the level.

It really would have been awesome if they had upgraded the blitter in AGA to handle it.

Wasn't that one of the major let downs of the AGA machines? That and the sound chip had remained the same.

slaapliedje

[lordofchaos]

I have some questions about Amiga disk formats. I know there is the standard DOS format disks which you can read from wb etc, along with the custom NDOS formats..I know a lot of demos and games use their own custom loading formats.

What are the real advantages from using custom disk formats? Are they usually quicker, more efficient? Can you squeeze more data onto a disk that uses it's own custom format?

Oh and one last thing why are some disk loaders so dam loud?

[Mrs Beanbag]

There is a certain amount of space overhead for Original Filesystem including a good deal of redundancy, so if you don't need the flexibility of a full-fledged filesystem it makes sense to use a custom format. Although a lot of games did seem to take crazy time to load, with a lot of thrashing. I don't know if it was because the custom format wasn't very well thought out. It also makes it more difficult to copy the disk or to hack the files.

Some games used "long tracks". I'm not sure how this works exactly but you could store more data in a track than usual, but while this is possible to read easily you need special hardware to write it so it's impossible to copy, this is why cracked games sometimes use more disks than the original.

[StingRay]

Originally Posted by lordofchaos

What are the real advantages from using custom disk formats? Are they usually quicker, more efficient? Can you squeeze more data onto a disk that uses it's own custom format?

More data fits on the disk since f.e. the directory tables and all the other DOS stuff is not needed. Also, you can arrange the files exactly the way you want and the files can't be accessed that easily by other people. And, if the loader code is good and the disk layout well thought out, loading is much faster as well. When it comes to games, custom disk formats are mostly used for copy protection (long tracks etc.).

Originally Posted by lordofchaos

Oh and one last thing why are some disk loaders so dam loud?

That's because they always step back to track 0 and then seek to the track that needs to be loaded. Either the coder was lazy or the loader code has to be very small.

[mr.vince]

Custom loaders could save money. By arranging the track start of adjacent tracks replicators were able to copy in one pass without waiting for index information. So a good format would give you more space, faster loading on the target and would be cheaper to replicate as the disk would be ready in e.g. 35 seconds instead of 50. In the end, most things were about money.

[wanderer]

I still cannot believe Turrican II comes on a single floppy.

[lordofchaos]

@Mrs Beanbag, StingRay. Thanks for the info, makes more sense now. So some developers could both protect their games and have faster loading routines if they knew what they were doing.. I suppose in some cases the actual protection systems could cause longer load times if not done efficiently.

[mc6809e]

Originally Posted by Mrs Beanbag

Some games used "long tracks". I'm not sure how this works exactly but you could store more data in a track than usual, but while this is possible to read easily you need special hardware to write it so it's impossible to copy, this is why cracked games sometimes use more disks than the original.

Paula has an internal clock that tracks syncing information in the bit stream as it comes off the disk. Bits that come in more quickly than normal are still readable. This allows more bits per track.

It should be possible to write denser tracks with a regular Amiga by slightly reducing the rotation rate of the floppy drive motor while writing to the disk.

[HardStep]

Is it possible to use clockport Delfina with Octamed Soundstudio?

[Marcuz]

Is the maid in the Shadow of the Beast II's intro with one arm only? This bugs me since a couple of decades...

[TCD]

There's definately something wrong about her left arm. Maybe something went wrong at the mastering of the intro or the animator just didn't have the time to finish that part? Would be interesting to find out what went wrong there.

[Marcuz]

Yeah! I used to wonder if it got lost on the same color on the floor but I'm not so sure. There are things in that animation that I did not get right away, like all that drama seemed disproportionate to the actual deed, or how it related to the first chapter.

[s2325]

Maybe she is searching for weapon in pocket. Or it's just perspective problem.
Hand salvaged with magic: