To answer the OP, according to the ARM Holdings website for handheld/handset use the frequency range they're estimating is 1-1.5GHz. The Cortex A8 is rated, by them, at 2.0 DMIPS/MHz and the Cortex A9 at 2.5 DMIPS/MHz. The Cortex A15 is supposed to be triple issue and thus represent a 50% higher throughput versus the dual issue Cortex A9. There are some indicators of performance inmprovements beyond this, but nothing verifiable as ARM Holdings doesn't actually have performance specs listed yet for the Cortex A15. As a result the following won't assume these performance improvements are significant.
So if you assume 1.5GHz:
-Not being able to exploit triple issue: P2~3.125 P1s (600Mhz)
-Able to fully exploit triple issue: P2~4.688 P1s (600MHz)
-Able to fully exploit dual core & triple issue: P2~9.375 P1s (600MHz)
-As I understand it Dosbox emulation is currently supposed to be in 386 territory, which means it should be in the territory of a decent 486. Pentium in terms that are meaningful and thus in theory supporting the entire DOS catalogue would seem unlikely.
-Fifth Generation to Sixth Generation consoles was a rather big leap. Purely in terms of MHz the PS2 was 8.9 times faster then the PS1 and the Gamecube 5.184 times faster then the N64.
So in terms of back of the napkin calcs it should pick up a few consoles, but the main improvements would be in terms of native applications and emulated computer systems (Amiga, DOS, etc.). The Cortex A7s that may be packaged with the Cortex A15s should approximate the current Cortex A8 in terms of performance while offering better power consumption characteristics during period of low usage thanks to various improvements in things like gating and process.
