On 2012-10-17, at 17:16, Gerrit Heitsch wrote: >> Now time to think about 27C512 with place for more KERNALS. Since I want at least three (CBM, Dolphin, Jiffy) 512 with some sort of encoder switch will have to do until Michau builds our ultimate ROM replacement board.. > > Good to hear that the logic itself was sound, just a bit of missing copper kept it from working. Yes, started to work with the first shot after I added the missing connection. As I wrote I was already running out of ideas what could be the problem. I made somewhat better layout (manually routed instead of simple autorouting, no vias and no extra wires needed): http://dl.dropbox.com/u/58002657/cbm/c64/rom_adapter_pcb_1.png > Now, for the 27C512 and more kernals... Well it means you have space for 4 KERNALs in the second half of the EPROM, making it 6 total. > > Until you need more than 4, an easy way might be to connect A15 at the EPROM to _KERNAL and then use the multiplexer trick again. I don't need more than four but I don't like semi-solutions as you may have noticed ;-) Meaning if I am to have room for six and can't use that room for anything alse (can I?) [*] then I rather go the extra mile and allow using all six. > Meaning if _KERNAL is HIGH, you use A14 and A13 of the EPROM to select BASIC and Char-Set(s) and if _KERNAL is LOW, you use them to select your KERNAL. > > I'll have to think about it in detail... * - how about using the extra space for selecting-in some cart images? I mean I have a need for three KERNALs. Can imagine a need for four. Beyond that I find it difficult to imagine a daily use setup that would need more KERNALs always present. But I can imagine using e. g. three or four KERNALs and one or two or three ROM cart images that would autoboot with CBM80 when selected at $8000. To make it best as I can think of now I would use the room for four KERNALs and two ROM carts. -- SD! Message was sent through the cbm-hackers mailing listReceived on 2012-10-17 23:00:06
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