Amiga Vs ST

[Thorham]

Originally Posted by Cyprian

yep, that's obvious that in terms of blitting data Amiga was better but in terms of computing power ST was better

Not to mention that for 3D you might be able to combine normal blitter fills with sprite+copper fills on 16 color screens (fill edges with sprites for eight pixel boundaries, blitter can be used here, too, use the copper for the rest, and what can't be filled that way is filled with the blitter... or something like that). Maybe

[lordofchaos]

Originally Posted by Havie

Apart from the music and smoother gradient.

Of course but I am only speaking strictly in terms of 3d performance.

[mc6809e]

Originally Posted by Cyprian

ok, actually I know (thanks to you and Toni) how to calculate blitting cycles. In py post, I asked about how many blitter registers CPU have to write in order to initialize such a blitter copy. I'd just like to calculate how many CPU cycles that initialization takes and where is worth to use CPU and where blitter.

The first initialization before beginning the horizontal line drawing loop would take a large number of writes (five longwords and four words), but after that first initialization, many of the registers would stay the same and wouldn't have to be reinitialized. An arbitrary bit block copy isn't necessary either since the horizontal line looks the same whether it's shifted or not.

I count one longword write, and four word writes per copy of a horizontal line, assuming all other registers have been initialized beforehand and that the frame buffer and source lines don't cross 128K boundaries -- one longword write is for the masks on the source A which points to the stored horizontal line, three word writes for the lower 16 bits of each of three pointers, and one word for the size which starts the blit.

Such a copy would use DMA channels BCD. That would take between 8 CPU cycles per word in the best case (during overscan and blanking) and 16 CPU cycles per word in the worst case (during display, sprite, refresh, disk, or audio DMA).

Originally Posted by Cyprian

what kind of code do you mean?

I know that blitplanes have an impact onto CPU. If my calculations are correct in mode 320x256 mode, in case of 5bitplanes, ST is faster by 24% and in case of 6bitplanes 37%. In case of 320x200 mode 21% and 31% respectively.

Your calculations are only correct if you assume that all instructions need to access memory on absolutely every fourth cycle. That doesn't always happen.

Suppose code includes many MULSs and DIVSs (a 3d game with filled polys, for example). Those instructions spend most of their time processing internally. The extra cycles taken for the display would only modestly slow down those instructions because display DMA fetch can occur at the same time the instruction is running.

[pandy71]

Originally Posted by Cyprian

I know that blitplanes have an impact onto CPU. If my calculations are correct in mode 320x256 mode, in case of 5bitplanes, ST is faster by 24% and in case of 6bitplanes 37%. In case of 320x200 mode 21% and 31% respectively.

??? how the heck ST can have 5 or 6 bitplanes? Or in other words - what do you need to do to have 5 or bitplanes on ST - how many CPU cycles?
Classic case - mouse pointer - how many CPU cycles are used on ST to simply simulate HW sprite? Everyone calculate CPU cycles but we can't ignore OS overhead or typical functionality required by GUI.

[Cyprian]

Originally Posted by mc6809e

Your calculations are only correct if you assume that all instructions need to access memory on absolutely every fourth cycle. That doesn't always happen.

yep, my calculations are pure theory, and it's just rough estimation. But I'm going to do some real tests. I'd like to compare decompression time for some packers like lz4, lz77, lz78, arj ect. in different video modes. But at the beginning I have to learn some basics of AmigaOS

Regarding blitter, I read somewhere here about 450 cycle initialization for blitter line routine, and I was curious how it looks in case of copy data initialization. That initialization (five longwords and four words) looks pretty good.

Originally Posted by pandy71

??? how the heck ST can have 5 or 6 bitplanes? Or in other words - what do you need to do to have 5 or bitplanes on ST - how many CPU cycles?

I've just compared performance for popular video modes on ST and Amiga. And as I mentioned, those figures are pure theory.

Originally Posted by pandy71

Classic case - mouse pointer - how many CPU cycles are used on ST to simply simulate HW sprite? Everyone calculate CPU cycles but we can't ignore OS overhead or typical functionality required by GUI.

good point. At the beginning I had an idea to compare only pure hardware with OS switched off. Now I'll try to compare also performance under OS under different video modes. Unfortunately I have no idea yet, how to change video mode in a clear, OS compatibly way. Can you advise me with links to AmigaOS for dummies?

[mc6809e]

Originally Posted by Cyprian

Regarding blitter, I read somewhere here about 450 cycle initialization for blitter line routine, and I was curious how it looks in case of copy data initialization. That initialization (five longwords and four words) looks pretty good.

There are only 14 words of registers that have to be written to for line draw if nothing else is already setup. Once things are setup, usually just 8 words.

I think the 450 cycle initialization is for arbitrary lines and includes computation of deltas (which has to be done for a software-only line draw, too).

Of course the key to maximum speed is getting the blitter to run at the same time as the CPU.

With line draw deltas and other values can be computed by the CPU while the line is being drawn by the blitter (er, I mean many of those calcs can be done while the line is drawn by the blitter with little slow down).

[turrican3]

The most beautifull games are on amiga, teh atari st couldn't achieve this games and that's all in 3d games the atari wins ok but the amiga version is very close. But a game is programmed on amiga it blows the atari st away.
And if somone say that is not true, he's just trolling.
I had an atari st in prior but i changed very fastly for an amiga, it was clear that the atari st couldn't achieve what i saw on amiga.

[s2325]

Extensor is fast and smooth on both machines http://hol.abime.net/2899 Main problem is turning llike in old RPG games.

[pandy71]

Originally Posted by Cyprian

I've just compared performance for popular video modes on ST and Amiga. And as I mentioned, those figures are pure theory.

So compare 640x200 4 color (standard WB screen on Amiga and i assume on TOS), side to this compare 320x200 16 colors (i have same discussion with another enthusiast to compare plain vanilla A1200 with Atari Falcon where only DSP is capable to do 30MIPS) - please always care about details when such comparison is performed.

Originally Posted by Cyprian

good point. At the beginning I had an idea to compare only pure hardware with OS switched off. Now I'll try to compare also performance under OS under different video modes. Unfortunately I have no idea yet, how to change video mode in a clear, OS compatibly way. Can you advise me with links to AmigaOS for dummies?

You can compare plain HW but still compare it fair or plain CPU power (then no miracles expected and Amiga CPU clock by clock will be slower approx 10.5%) or system performance (thus Amiga will be faster thanks to Copper, sprites, PCM audio with DMA, blitter etc).

System overhead can be very difficult as user behavior will be not repeatable.
And sorry - i never coded under Amiga OS.

[dlfrsilver]

The ST is computer you need to code all in software since the main CPU drives everything and handles everything. The amiga is not an ST, it's a multimedia computer, with hardware acceleration abilities. Not using them is non sense, and not conform to what the amiga was made for.

[lordofchaos]

Here's another side by side comparison for your viewing pleasure, this time Lemmings.

[ Show youtube player ]

[lordofchaos]

Quite surprised with this comparison, seems the ST version comes out on top, surprisingly the sound seems better on ST too.

Vroom. [ Show youtube player ]

[Neil79]

Originally Posted by lordofchaos

Quite surprised with this comparison, seems the ST version comes out on top, surprisingly the sound seems better on ST too.

Vroom. [ Show youtube player ]

More trebbled

[s2325]

thanks for videos

[lordofchaos]

You're welcome, it's quite fun going back and playing these again, even if I have to play with the video capture lag

Yup, prefer the sound on the Atari version.

@s2325. Oh and thanks for subbing, returned in kind.

[dlfrsilver]

Well not exactly : first, the amiga version is faster than the ST version (what a surprise ahah ), and the sound is NOT better on ST.

The lankhor guys have not removed the sound filter on amiga ! It needs to be patched to get the title sound as good as the ST version

[lordofchaos]

Originally Posted by dlfrsilver

The lankhor guys have not removed the sound filter on amiga ! It needs to be patched to get the title sound as good as the ST version

Hmm, interesting. I didn't know that. Still nice to hear sampled engine sounds from the ST for a change.

[s2325]

I think Action Service for Atari ST [ Show youtube player ] have better music than for Amiga https://youtu.be/Pia4NOJVgMo?t=48