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Old 27 September 2022, 07:17   #61
hammer
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Originally Posted by Thomas Richter View Post
That does not make too much sense. AGA graphics is only planar, with up to 8 bitplanes. RTG graphics can do planar, but only up to 4 planes, or chunky. Thus, emulating AGA with RTG would either limit you to 4 bitplanes (which does not make much sense) or an always running, costly planar to chunky conversion. Also, for emulating the copper, RTG would need to run in true-color or hi-color mode to offer sufficient colors, IOWs, even more conversions needed.
OP wanted FireBird V4's FPGA AGA feature on PiStorm/Emu68 with the C= Amiga hardware being reduced to a user input device role.
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Old 27 September 2022, 23:15   #62
Bruce Abbott
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Quote:
Originally Posted by Thomas Richter View Post
That does not make too much sense. AGA graphics is only planar, with up to 8 bitplanes. RTG graphics can do planar, but only up to 4 planes, or chunky. Thus, emulating AGA with RTG would either limit you to 4 bitplanes (which does not make much sense) or an always running, costly planar to chunky conversion. Also, for emulating the copper, RTG would need to run in true-color or hi-color mode to offer sufficient colors, IOWs, even more conversions needed.
On the contrary, it makes perfect sense to use true-color in an emulator. All the video hardware is emulated up to the point where it comes out as RGB or composite, then it's rendered on the host in an appropriate screen mode. Sure it's costly, but the only practical way to ensure accurate emulation when the foreign and native video systems are so different. As far as the host's graphics system is concerned it's just an image like a photo or frame from a movie, and how it was generated is irrelevant.

It's not the most costly way though. Emulators for early video game machines go down another level - simulating the logic gates and analog components via a netlist generated from the circuit diagram. That way they can use a generic electronic circuit simulator rather than having to write bespoke code for each machine. This is incredibly costly, but removes the burden of having to understand how the emulated machine works.

The extreme cost in CPU cycles may seem incredibly wasteful, but the savings in development time and higher accuracy more than make up for it - provided the host machine is fast enough. The PiStorm should be fast enough to emulate AGA graphics, but unfortunately that hasn't been done yet. So currently our only options are to run a standalone Amiga emulator on the RPi (which would not be using any of the Amiga's peripherals), or to run an Amiga emulator on the Amiga itself (which does use its peripherals) using the RPi as a very fast 68k CPU and RTG graphics. So we have an ARM CPU emulating a 68k CPU emulating a 68k CPU and Amiga chipset!

Sounds impossible? With sufficient processing power anything is possible. Claims have been made that with JIT a 68k CPU emulator can approach native speeds- ie. a 1:1 correspondence between 68k and ARM instructions. The RPi has 4 cores running at 1.4 GHz. Will this be enough?
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Old 29 September 2022, 07:23   #63
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Sounds impossible? With sufficient processing power anything is possible. Claims have been made that with JIT a 68k CPU emulator can approach native speeds- ie. a 1:1 correspondence between 68k and ARM instructions. The RPi has 4 cores running at 1.4 GHz. Will this be enough?
FYI, A500Mini can run AGA games via emulation. [ Show youtube player ]

A500Mini features Allwinner H6 SoC with a Quad-Core Cortex-A53 ARM CPU (up to 1.8Ghz) and Mali-T720 MP2 GPU from ARM. Allwinner H6 SoC's Quad-Core Cortex-A53 ARM CPU is the same as RPI 3a's and RPI Zero 2W's Broadcom SoCs.

RPI 3a+'s Quad-Core Cortex-A53 ARM CPU's 1.4 Ghz can be overclocked to 1.8Ghz OC with the warranty being void.

I don't believe in 1:1 correspondence between 68k and ARM instructions. ARM can't do fused instructions like performing arithmetic on a memory location like on 68K or X86 CPUs, e.g. the RISC CPU needs to perform load and math atomic operations and it consumes at least two instruction issue slots.

ARM cores can only perform data processing on registers, never directly on memory. CISC's fused instructions are closer to VLIW CPU's instruction issue that can contain multiple instructions.

For WHDload games, I usually set Emu68's JIT cache to 2 and disable 68K cache to slow down the emulated CPU. I modified WHDload's start-up and clean-up script files to set between "classic Amiga game mode" and "DraCo RTG mode".
-------------
With Linux ARM, RPI 3a+/3b+ can do ioqQuake III at about 100 fps via the Vulkan driver. [ Show youtube player ]

From https://www.anandtech.com/show/742/5
PC's Quake III benchmarks from GeForce 3 Ti and AMD Athlon-C (Thunderbird) 1.0GHz.

Last edited by hammer; 29 September 2022 at 08:14.
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Old 29 September 2022, 11:21   #64
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FYI, A500Mini can run AGA games via emulation.
You really are missing the point of his thread. We all know AGA emulation is possible on numerous different devices, but the OP was asking about doing it on the OG hardware. Whether PiSorm et al reduce this hardware to a mere IO machine is a moot point in this particular scenario.
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