The Ideal (Hypothetical) Gaming Processor
Hi everyone. I've been wondering what the "best" types of gaming CPUs would be, and I would like to know what it takes to make an idealized gaming-oriented processor.
Suppose I had a fabless semiconductor company, and I was contracted to design the CPU for a new game console. The GPU was already determined to be something relatively powerful, like a die-shrunk Radeon HD 6870. The goal is to make the chip as small and cheap as possible, but will never bottleneck the graphics processor.
What sort of difference does a processor's ISA make? Suppose I had licenses for MIPS, ARM, SPARC, and other risc-based architectures. Is the ISA really that important, or just the micro-architectural "plumbing" underneath?
What types of instructions do modern video games make the most use of? Do games find integer performance most important, floating point performance, or both? If floating-point calculations can be offloaded to the GPU, can the CPU's floating-point units be excised to make the chip smaller and cheaper, or would that harm system performance? If FP power is still important, would adding complex 256- or even 512-bit units be beneficial to total system performance, or just a waste of space?
How important is cache size? Intel's SNB i5, i7, and SNB-E i7 processors have 1.5, 2.0, and 2.5 MiB of L3 cache per core, but looking at benchmarks from Anandtech and other places, there doesn't seem to be too much difference. At least, not enough difference to justify the added space and expense. How much cache per core is "enough"?
As for the core count itself, would it be best to make a quad-core chip and call it a day? I know most game engines today simply do not scale past four cores, and simultaneous multithreading is pretty much useless for games. But, since consoles are expected to last around 5 years, would making a 6- or 8-core CPU prove beneficial in the future, so long as the chip stayed within the client's budget?
I know this is just a lot of speculation, but I'm just curious what makes games tick.