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Old 09 September 2014, 00:41   #461
s2325
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Hellgate preview for Atari ST is so slow and jerky it's unplayable. I don't think it can be any better on Amiga 500. Anyone tried that game?
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Old 09 September 2014, 01:03   #462
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That's what he said. that ST is a little (very little) faster. Using only the CPU, this additional mhz in ST gives to a pair of more frames.

Spanish games? you're right, but those games are (more or less) of 88-89 in those years almost all companies in any country, converted directly from AtariST.
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Old 09 September 2014, 08:39   #463
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That's what he said. that ST is a little (very little) faster.
ST was faster by 11%
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Old 09 September 2014, 10:43   #464
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very little.... it's unoticeable in games.
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Old 09 September 2014, 12:55   #465
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You kidding? all the bad blood of Amigans towards ST is because of THIS original sin of the developers - whoops - greedy publishers!!!
It wasn't anything new in the software industry though, Atari 8-bit and C64 received ported Apple II games to begin with (and some of the best known C64 titles are actually Atari 8-bit ports like Boulder Dash or Bruce Lee) whilst the Amstrad CPC and MSX ended up with quite a few straight Spectrum ports from the UK market.

Some of it was down to developers but in a lot of those cases the "port and be damned" route was taken because the publishers had only stumped up enough time or cash to cover development of one bespoke version. i doubt many devs were happy with that decision...
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Old 09 September 2014, 13:35   #466
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very little.... it's unoticeable in games.
11 percent is enough to see a difference in Frontier: Elite II:
[ Show youtube player ]
and other vector games
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Old 09 September 2014, 14:20   #467
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11 percent is enough to see a difference in Frontier: Elite II:
[ Show youtube player ]
and other vector games
Probably only when they don't use the blitter.
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Old 09 September 2014, 15:01   #468
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Probably only when they don't use the blitter.
yep, that's obvious that in terms of blitting data Amiga was better but in terms of computing power ST was better
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Old 09 September 2014, 15:14   #469
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11 percent is enough to see a difference in Frontier: Elite II:
[ Show youtube player ]
and other vector games
The difference in this example being minimal.. Faster yes but in the context of playing the game on these stock machines.. Another example of a 3d game coded by very competent developers, (especially on the ST) is No Second Prize.

[ Show youtube player ]

Once again this demonstrates another photo finish, both machines showing no real tangible difference.
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Old 09 September 2014, 15:52   #470
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Yes and even no second prize makes no use of the blitter, it's all done in software......
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Old 09 September 2014, 18:04   #471
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well, when i look at the best made amiga games, i see that amiga coders got the best out of the machine. What's the point of mastering the 68000 to the maximum on amiga, is there any convenience out of gaining some cycles ?
I thought we were talking about rather early stuff.. not the time when folks actually learned to squeeze last bits out of Amiga's co-processors.
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Old 09 September 2014, 20:59   #472
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ST was faster by 11%
Being ignorant on ST.. did it have similar issues with memory access what Amiga had when the code was running in CHIP RAM?
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Old 09 September 2014, 22:36   #473
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Being ignorant on ST.. did it have similar issues with memory access what Amiga had when the code was running in CHIP RAM?
yep, ST-RAM is equivalent of CHIP RAM, where CPU can be a bit slowed down by e.g. HardDisk DMA channel or BLiTTER, and ALT-RAM is equivalent of Fastram.
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Old 09 September 2014, 22:40   #474
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In many ways the CPC share some things with the amiga (CRTC/hardware scroll/palette change - Copper/Blitter/hardware scroll/Palette change)
Once again to clear incorrectness - CPC use MC6845 as CRTC - graphic capabilities are very similar to CGA graphic card well known in PC world.
There is no such things as blitter in CPC. AFAIR Amiga was very first popular computer with blitter implemented in hardware.

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yep, ST-RAM is equivalent of CHIP RAM, where CPU can be a bit slowed down by e.g. HardDisk DMA channel or BLiTTER, and ALT-RAM is equivalent of Fastram.
AFAIK when 4 bitplane lores are used there is no slowing CPU so up to 4 bitplanes in lores only difference will be a CPU clock.

Last edited by TCD; 09 September 2014 at 23:04. Reason: Back-to-back posts merged.
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Old 09 September 2014, 22:57   #475
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AFAIK when 4 bitplane lores are used there is no slowing CPU so up to 4 bitplanes in lores only difference will be a CPU clock.
yep
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Old 09 September 2014, 23:00   #476
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The difference in this example being minimal.. Faster yes but in the context of playing the game on these stock machines.. Another example of a 3d game coded by very competent developers, (especially on the ST) is No Second Prize.

[ Show youtube player ]

Once again this demonstrates another photo finish, both machines showing no real tangible difference.
Apart from the music and smoother gradient.
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Old 11 September 2014, 18:07   #477
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interesting point.
do you know how many blitter registers CPU have to write to do such a operation and how many cycles it eats?
Am I right that, you have to repeat that blitter init operation for each bitplane?
Bitplane rasters can be interleaved on the Amiga. Bitplane one's first raster is followed by bitplane two's raster is followed by bitplane three's first raster, etc.

This mean that when blitting to a standard 16 color display, you can treat the screen as a single 320x800 bitmap and blit once.

Not sure how many cycles it eats, but in some cases those cycles are free since the the blitter is capable of accessing memory every two CPU cycles while the CPU is only fast enough to access memory every four CPU cycles. This means that DMA cycles that would be wasted on other platforms (like the ST) can be used by the blitter on the Amiga.
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Old 11 September 2014, 18:11   #478
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ST was faster by 11%
Depends on the code.
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Old 11 September 2014, 19:19   #479
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yep, ST-RAM is equivalent of CHIP RAM, where CPU can be a bit slowed down by e.g. HardDisk DMA channel or BLiTTER, and ALT-RAM is equivalent of Fastram.
You're confused. ST-RAM is not the equivalent of chipram.

On the ST, the "MMU" absolutely restricts the CPU (and later the STE blitter) to accessing memory on four CPU cycle boundaries. There are also large amounts of potential bandwidth that go unused during overscan and blanking.

On the Amiga these extra cycles are usable, for example by the blitter, or hardware sprites, or audio, and in some cases by the CPU.

This can make some blitter operations appear to come at no cost. A memory clear by the blitter during overscan is done almost for free with little CPU slowdown.

Chipram can also allow the CPU to access memory at times when ST-RAM would block the access.

Code:
loop:
          move.w (a0)+, d0 ; 8 cycles
          bne.s loop ; possibly 10 cycles on Amiga but always 12 cycles on ST
done:
          ...
There are two internal CPU cycles at the beginning of the bne instruction if the branch is taken. This causes the first prefetch cycle of the bne instruction to fall on a cycle boundary that isn't a multiple of four. On the ST, this adds two wait states. But on the Amiga, if no other DMA is occurring, the CPU will not be made to wait.

This difference is small, admittedly, but it reduces the effect of the clock rate difference between the ST and Amiga.

In the above example, if the code runs during vertical overscan (in a Vblank int handler, for example), the ST will need to execute 20 cycles per loop while the Amiga will average slightly more than 18 cycles per loop.
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Old 11 September 2014, 19:40   #480
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Bitplane rasters can be interleaved on the Amiga. Bitplane one's first raster is followed by bitplane two's raster is followed by bitplane three's first raster, etc.

This mean that when blitting to a standard 16 color display, you can treat the screen as a single 320x800 bitmap and blit once.

Not sure how many cycles it eats, but in some cases those cycles are free since the the blitter is capable of accessing memory every two CPU cycles while the CPU is only fast enough to access memory every four CPU cycles. This means that DMA cycles that would be wasted on other platforms (like the ST) can be used by the blitter on the Amiga.
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.

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Depends on the code.
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.
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