newb question on EE, SH-4, Gekko

[Anarchist420]

Which one has the best IPC?

If the SH-4 was 180 nm instead of 250 nm, then would that have had better performance/watt than the GC's CPU (which actually was 180 nm)? If not, then how close would it have been?

Finally, which of the following would be the best (take into account TDP, peak performance, sustained performance, ease of programming/quality of documentation, precision, and cost) for a console released in 2001:

the PS2's CPU + Vector units (as they were);
the GC's Gekko (as it was);
an SH-4 except 180 nm, running at 480 MHz (and no more cache latency than the one in the DC had), and 32 MB SDRAM (instead of 16 like it had in the DC) on 128 bit external data bus (instead of 64 bit)

I was thinking the SH-4 I described since the other two could only do 32 bit FP precision (even though most think DP isn't necessary).

 

[Anarchist420]

If the questions don't make sense, then let me know how they don't make sense.

 

[Fox5]

IPC is going to depend on the type of code.

If the SH-4 were 180nm, it would have been a different cpu. Why not ask if it were 90nm? It's hard to say about IPC, but Gecko was probably both higher IPC and higher clock, it was pretty much a desktop class cpu versus the mobile derived SH-4 cpu.

Dreamcast had a bigger burden on the cpu, because it had a primitive graphics processor. The EE on the Ps2 was made to handle more of the graphics workload, so it was much more powerful at floating point with its two VUs.
The Gamecube fell somewhere in between in floating point capability (with a slightly more capable gpu than either) but by far had the most powerful general purpose processor of the 3.

It's very unlikely the clock frequency of the SH-4 would have more than doubled to 480mhz just from a shrink to 180nm. And even at that speed, Gecko is probably still a more powerful general purpose processor. Remember, Gecko is comparable to a Pentium 3, which still puts modern day ARM cores to shame in IPC. EE was a MIPS design, and the best MIPS designs today are comparable in IPC to the best ARM designs. SH-4 is basically dead, and is unlikely to match even modern day ARM and MIPS in IPC.
The SH-4 had the lowest floating point performance of the 3, and no hardware on the graphics processor to offload graphics calculations to. Even the Naomi 2, a suped up arcade version of the same hardware, at best traded blows with the PS2 and Gamecube. (better in some ways, mainly amount of memory available, but still worse in others)

 

[Anarchist420]

Thanks

 

[nenforcer]

Don't forget the Hitachi SH-4 had some dedicated hardware for vector conversion / matrix multiplication and matrix inner (dot) product which helped to alleviate some of its manufacturing / gpu design shortcomings.

It's unfortunate that the later Renesas SuperH designs haven't seen much usage outside of the Japanese automotive industry.