Yes, I'm still harping on. Sorry :-) Edwin wrote: > Like the Idea. So I looked a bit better at LDIR in ROM too. > > LDIR is made up of 5 M-cycles: > 4,4,3,5,5 for standard LDIR = 21T > 4,4,3+1,5,5+2 LDIR in RAM with RAM contemption = 24T > 4+4,4+4,3+5,5,5+6 LDIR in RAM with Display contemption = 40Ts > 4,4,3+1,5,5+2 LDIR in ROM with RAM contemption = 24Ts
See I disagree about this... Won't it be [4] [4] Loop around: {3},{1 WAIT} 4 cycles {5},[3 of 5] 8 cycles [2 of 5],[2 of 4] 4 cycles [2 of 4], {2 WAIT} 4 cycles or 20 t-states per byte? (plus initial setup, of course) > When looking at a LDI: > 4,4,3+1,5+3 LDI in RAM with RAM contemption =20Ts > 4+4,4+4,3+5,5+3 LDI in RAM with display contemption =32Ts > > From the above timings you can see that a block of LDIs is 4Ts or > 16.6% per byte faster then a LDIR (anywhere) during RAM contemption. Don't think so. > But during display contemption a LDIR in ROM is as fast as a LDI in RAM. This is true. To clarify: LDIR in ROM, RAM contention [4] [4] Loop around: {3},{1 WAIT} {5},[3 of 5] [2 of 5],[2 of 4] [2 of 4], {2 WAIT} LDIR in ROM, DISPLAY contention: [4], [4] loop around: {3}, {5 WAIT} {5}, [3 of 5] [2 of 5], [4], [2 of 4] [2 of 4], {6 WAIT} ie 32 t-states LDI in RAM, RAM contention: {4} {4} {3}{1 WAIT} {5}{3 WAIT} Still 20 t-states. So RAM-contended RAM-based unrolled LDIs are as slow (fast) as ROM-based LDIR. LDI in RAM, DISPLAY contention: {4}{4 WAIT} {4}{4 WAIT} {3}{5 WAIT} {5}{3 WAIT} 32 t-states. So display-contended RAM-based unrolled LDIs are as slow (fast) as ROM-based LDIR too. Of course you still have additional CALL/RET times (32 RAM-contended or 64? DISPLAY-contended) but that plays against the issue of the inflexibility of unrolled LDIs. Or am I (still!!) missing something? Geoff ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________