Subject: Re: [stella] programming teaser From: "Fred Quimby" <c9r@xxxxxxxxxxx> Date: Fri, 20 May 2005 17:45:04 -0400 |
What bankswitching scheme are you using? I ask because I'm not aware of any that allow multiple banks of RAM except for E7 or Starpath, and the Kroko cart doesn't support these. >The whole point being that in a kernel you don't necessarily need to >compare >a counter value, nor branch when it reaches the final value. In notBD, >there are n rows, each done by identical code in consecutive banks. By >switching banks, the code keeps running, but the last bank has a "rts" just >after the switch. It's an interesting technique, used in notBD's new >kernal >(worked on by Thomas and I) -- and without which, the kernel probably >wouldn't be possible. > >In answer to Dennis, this particular code runs in BOTH RAM and ROM. It's a >bit weird, but the code is defined in ROM, and you (can) call the ROM >routine still. But it is also copied to multiple RAM banks, and the first >bankswitch will switch to the code running in RAM (because, in the >bankswitch scheme I am using, there is only one switchable bank -- in an >address area shared by both the ROM-switchable and RAM-switchable banks). > >Another way to achieve the same effect as the rather unique 'tricky' >subroutine would be with self-modifying code, but it costs cycles. The >above technique is totally cycle-free in terms of detecting and forcing the >end of a loop. You do, of course, need the right memory architecture to >achieve this :) > >Cheers >A > > >----- Original Message ----- >From: "Thomas Jentzsch" <tjentzsch@xxxxxx> >To: <stella@xxxxxxxxxxxxxxxxxx> >Sent: Friday, May 20, 2005 9:07 PM >Subject: Re: [stella] programming teaser > > >Fred wrote: > > Maybe your bankswitching instruction swaps the code out after x=8 and > > finds > > an RTS where the ldy #21 was? > >Bingo! > >BTW: THAT one was solely Andrew's idea! ;-) > >Have fun! >Thomas >_______________________________________________________ >Thomas Jentzsch | *** Every bit is sacred ! *** >tjentzsch at web dot de | > > > >______________________________________________________________ >Verschicken Sie romantische, coole und witzige Bilder per SMS! >Jetzt bei WEB.DE FreeMail: http://f.web.de/?mc=021193 > >Archives (includes files) at http://www.biglist.com/lists/stella/archives/ >Unsub & more at http://stella.biglist.com > > >Archives (includes files) at http://www.biglist.com/lists/stella/archives/ >Unsub & more at http://stella.biglist.com > Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://stella.biglist.com
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