F9 Or of you prefer C3 00 00
On Oct 20, 9:20 am, opinali <[email protected]> wrote: > Ok, here's mine - for a real micro :) > > http://www.worldofspectrum.org/stk/http://www.worldofspectrum.org/infoseekid.cgi?id=0012128 > > Can't remember significant POKE'ing trivia, but can still write Z80 > Assembly to save my life, after almost 20 years... will probably not > remember only rarely-used instructions, including most undocumented > ones (Z80 had a ton of these). In the good times I'd write simple > routines in straight hexadecimal. It's amazing how well your memory > works when you don't have an IDE with auto-completion - or at least I > (we?) like to think that, because the alternative conclusion is that > my brain was better as a teen :) > > Now in the "it's never too late to learn" category, just a few months > ago I found some retro page explaining the fastest possible method for > copying blocks of memory with the Z80 - a critical operation for games > using double-buffering. I already knew that looping instructions like > LDIR/LDDR were slow and used simple unrolling; but there's an even > faster method, using the stack pointer to alternatively index the > source and destination blocks, loading as much data as possible into > all other registers (including the alternate ones) with POP > instructions, then writing with PUSH's, loop till end... this flies > because the 16-bit PUSH/POP instructions are 2X faster than equivalent > 16-bit LD's (probably true for other 8-bit CPUs too), plus you get the > src/dest address incs/decs for free. Only trick is disabling > interrupts because we are messing with SP. And of course, since PUSH > and POP update SP in inverse directions, your back-buffer must be all > upside-down so the block-copy routine doesn't need extra logic to > compensate for that. > > (Now let me return to my day job, i.e. >10-Mb footprint for HelloWorld > in any modern lang) > > On Oct 19, 10:57 am, Christian Catchpole <[email protected]> > wrote: > > > > > screen colour = black > > border colour = black > > cursor colour = white > > > (and i remembered that from 1987) > > >http://twitpic.com/2yzlcp -- You received this message because you are subscribed to the Google Groups "The Java Posse" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/javaposse?hl=en.
