On 26 April 2011 14:23, Tommo H <[email protected]> wrote: > > The 25fps is based on a hypothetical chip having the same access as the CPU > does currently. >
But would still take up the majority of the bus time, meaning you couldn't do anything _else_. > I also disagree about the significant amount of electronics on the grounds > that Zilog's native DMA part cost less than $10 even in 1989 > $10 in a unit costing £200 retail is a significant cost. > Filled vectors are going to be not a huge amount quicker unless you make > the hardware a lot smarter - you'd spend most of your time setting up the > external registers to fill objects one line at a time. > > Based on profiling my filled vector code (not the stuff I've released, > better stuff), something like 80% of the total cost is the filling, and > something like 50% of the cost of the filling is CPU logic rather than > memory bandwidth. So the difference would promote a game of Mercenary > graphical complexity from unplayable to playable. > Erm, so you're saying that 40% of cost would be LDIRs replaced by 4 OUT instructions (say) and a wait while the DMA does its job (at say 50% of the original t-states of the LDIR itself)? I still don't buy that it would be any faster. You'd have to be blitting lines of more than about 20 pixels just to break even. (figures based on thumb-in-the-air estimates, so I'm probably quite a lot out, but you get the idea) G
