The candidates are:
- Apple IIgs, with its 2.8 MHz 65816 CPU, running in 65C02 "emulation mode"
- Apple //c+, with 4.0 MHz 65C02, but overclocked to 8.0 MHz
- Laser 128EX with 3.6 MHz 65C02
I want to know which is fastest for real world applications, like running AppleWorks, a BBS, terminal emulation, assembler/debugger, etc.
The reason I'm thinking the answer is not simply "It's the 8 MHz one, dummy" is because of memory architecture - i.e. How does each machine access standard program RAM and at what speed. I know the //c+ essentially has an on-board accelerator that relies on SRAM cache for full-speed CPU operation. The IIgs has no cache. I don't know about the Laser memory architecture.
NOTE 1: It's reported that the //c+ can be successfully overclocked to 10 MHz, but I have not had that working with any stability. 8 MHz seems stable.
NOTE 2: I'm sure we (meaning me personally) could try to validate the correct answer with a suitable benchmark run on all 3 machines. I don't know a good benchmark to use, and would welcome that info as part of an answer. The key is the benchmark would have to account for use of cache appropriately. Any benchmark that runs fully from cache would skew results in favor of the //c+. A realistic benchmarking suite probably existed at some point in the Apple II's lifespan.
NOTE 3: The correct answer is certainly NOT the IIgs running in native mode. That's not even an "Apple II", since it wouldn't run the legacy software library in that mode.
NOTE 4: I know this is a "hard question". I've not found any information online about how the 65C02 was interfaced to main memory in these machines, and what impact that had on overall system performance. My gut feeling is that the SRAM cache is a hack, and high-speed access to main memory should be the big performance differentiator.