From: Jim Brain (brain_at_jbrain.com)
Date: 2007-11-08 01:52:09
email@example.com wrote: > Hallo allemaal, > > > @Jim: > >> You have heard of expansion part extenders, right? >> > > Of course I have, I don't live in Far-away-istan :) But FC3 doesn't like > other cartridges parallel to itself. And I also have bad experiences > with the switchable expanders. > And to return the ball: I have heard of expanders for the Userports :) > I have as well, but on this side of the pond, they are nowhere near as common. > Nope, no cart needed. Somewhere in the '80s I saw an ingenious solution > in a 64er magazine: replace the original ROM with a 27128 and connect > A13 to the cassette port. The C64 starts up with the software in the > upper part of the ROM, does what it has to do, copies a bit of ML into > RAM and from there it negates A13 of the 27128 and does a "JMP ($FFFC)". > Cool idea, but I think the point was he wanted something that anyone could enjoy, not just those who could pop open and undo the ROM. We also need to remember that newer rev boards did not have socketed ROMs > Regarding the automatic boot: using UTP we can reserve one line for > telling the system that the network is alive by pulling it High. The > first C64 to be started sees a (H) on this line and waits for its > masters hand to tell it whether to start up the network or not by > negating this line. All other C64's that are connected then see a (H) on > Don't you mean L? > this line and will automatically start the network software. You don't > want to use a particular C64 on this net? Simply disconnect it. OK, it > will assume that it is the first one on the net and thus awaits your > input but that is a small price IMHO. > This suffers if more than one machine power up at the same time (using your Wake-On-LAN idea below, all machines would see an H, right? > Why (H) and not (L) you may wonder? I'm thinking of a system where this > (H) powers a small electronic system that on its turn powers up all > connected computers: a wake-up-on-LAN function I mentioned yesterday. > The most simple thing that comes in my mind is a relay that switches the > power supply for the C64 to "ON". > > > >> It seems a token passing or some other collision >> avoidance scheme is needed. >> > > Using a token is the safest way but it also means that in one or another > way the C64 has to watch the network all the time to be able to pass the > token to the next C64. And if someone is running SW that disables the > network SW in some way, the token passing is stopped and the whole > network down. Using a master could solve this problem but that means an > extra C64 doing "nothing". > Only using up to, let's say, four computers, I would use collision > detection, Just as David described. But using five or more computers I > would start thinking of using a Master. > I was rather hoping something like the IEC ATN line would be a possibility, which would allow machines to ignore anything except ATN commands. jim Message was sent through the cbm-hackers mailing list
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