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Old 08 August 2014, 10:35   #1351
Join Date: Jun 2010
Location: out in the wild
Posts: 1,135
Originally Posted by AmiDog View Post

I don't agree. The wiki states that "Shown in the table are the measured values with screen switched off and all possible optimizations" and yet I've proven that, for the specific benchmark, you can get identical behavior, but improved performance, by actually enabling "all possible optimizations" on a SCPU.
I have changed the wording to represent what's really interesting for the user: Optimizations should not affect software compatibility. It's a bit like a car maker advertising that "his" car gets so-and-so many miles per gallon, but only with a special kind of tires, slightly higher air pressure in the tires, a/c switched off, all windows closed and no acceleration/breaking. You never reach those conditions in real life, and publishing such numbers is plain deception. I want my advertising to represent real-life numbers that the user can verify at home.

Originally Posted by AmiDog View Post
On the other hand, any C64 accelerator is rather pointless since 99% of the C64 software relies on specific timing and/or a fixed frame rate and doesn't benefit from a faster CPU.
Here's where more "mechanics" of the Chameleon accelerator kick in: First of all, the CPU inside Chameleon supports all illegal opcodes, which has never been done in an accelerator before, simply because you can't buy a >2MHz CPU that has all NMOS illegals. This allows especially crunchers/decrunchers to run a lot faster, as these bit-fiddling routines often make use of illegal opcodes.

Then there's the extended VIC bit of the C128, that also enables 2MHz mode in C64 mode, which is being used by decrunchers and even games like "new Uridium" and "new Paradroid". You can choose the Chameleon turbo to use this extended bit, so all software that makes use of the C128 2MHz mode can also take advantage of the Chameleon turbo. You can limit the Chameleon turbo to a certain speed in increments of 1MHz, so you can also get the exact same speed as a C128 in C64 mode at 2MHz (with the difference that the display won't be garbled).

In addition to that, we have an "IEC sensitive" setting that slows down to the original C64 timing when IEC (=floppy) accesses are taking place. This way, even software that has it's own fast loader will work flawlessly. As a result, you can run GEOS and high-spec applications such as Printfox at speeds that are truly amazing. Even Amiga DTP applications of the time don't get the execution speed of Printfox on the Chameleon.

Granted, many games are not playable with the turbo switched on. Here's where all the compatibility won't help: While the SCPU won't even let you start those games due to incompatibilities, you'll be confronted with a quick "game over" or some funny-broken graphics if the game doesn't like the higher CPU speed of the Chameleon. This is where you need to press the menu button, switch off turbo and let the game continue to run on a non-accelerated C64.

The turbo is really not meant for games, but for applications. There's quite a few customers who still use the C64 in a productive environment, much like there's quite a few of us who still use the Amiga in some productive manner. You just don't meet these people every day in the supermarket ;-)

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