firstname.lastname@example.org wrote: > Hallo Andre, > > > You don't clock the output of the MMU. When you access the MMU in the > Yes, if in MAP-MODE! But the point is to disable the map-mode for that moment. Yes, I understand that. I just think that you then cannot access the MMU in the lowest bank (where the MMU is active). > Simple question: If the 612 w/o latch will cause problems IYO, why is it used > in the AT and worked w/o any problem??? :-) I have no idea how it is used in the PC :-)) > I hope youunderstand the above is not meant to be a "I'm right, You're wrong > discusion". As I intend to build Big-PET using a 612, we soon or later will > find out anyway who was right. No problem with that :-)) I don't feel offended or so, and I hope you you don't feel as well. I think that's just a technical discussion between techies :-) > > But: when the opcodes take more/less time and/or the clock frequency > > is different, there is a problem. > > Only in software dependent timeloops. correct. > > There should not be part-cycle out of phase, as both CPUs should be > > coupled by Phi0/Phi2. If the 65816 is clocked at higher speed, it should > > be phase-locked to Phi0/Phi2. > > That I do understand but which Phi0/Phi2; the original one of the PET or the > one of the coupled 1541??? I am now putting the schematics of my emulation boards on the net (CPU and keyboard), you might want to look at it. I use the CS/A65 clock Phi2 for the emulated CPU in the VC1541. It worked. However, if you have circuitry depending on phase-locks between Phi0 and Phi2 I can (by jumper) use Phi0 from the emulated 6502, although I have never needed/tested it. I am also putting a "write-protect" diff for my CPU board on the web: using the MMU to map memory pages write-protected! > > One more comment: Is it that useful to use the MMU in the lowest > > bank $00****? As far as I know this bank has a special meaning for Stack > > etc in the 65816. > > No. OK, the stack can be place anywhere within Bank 00 but I don't see that as > a problem. My mean reason to enable it in Bank 0 is that I can address it using > the BASIC or the onboard Monitor of the PET. And both are NOT capable of > addressing another Bank. I don't know much of the 65816. Can one not run 6502 programs in another bank without the 6502 knowing it (probably except for the stack)? I mean, if you speed up the 65816, each stack access would be slowed down because you mapped the PET memory there... - but with the MMU you can after all map "fast" RAM even in bank0, right? Andre -- Email address may be invalid. Use "fachat AT physik DOT tu-chemnitz DOT de" ------Fight SPAM - join CAUCE http://www.cauce.org------Thanks, spammers... Andre Fachat, Institute of physics, Technische Universitšt Chemnitz, FRG http://www.tu-chemnitz.de/~fachat
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