Hallo allemaal, I really started soldering again: expanding a VIC-20 (with C64 power plug up) to 32 KB SRAM. I have done that several times before so that shouldn't be a problem. But it didn't work out this time: the Vic-20 died under my hands :( So I took another board and repeated all steps. First I removed the BASIC-ROM and soldered it on top of the System-ROM. Plus a wire from CS to pin 9 of UC5. Things worked fine. I placed a 24 -> pin convertor on the place where first the BASIC-ROM was seated. Made all needed connection and tested things: fine. Then I placed a 74LS11, 3*3AND, that should combine all RAMx and BLKx (except BLK5) signals. I placed the SRAM, CS line connected to +5V, still fine. Now I connected CS to RAM1 and I got a weird number for the amount of RAM: somewhere between the original 3583 and expected 4709 bytes. Replacing the SRAM solved the problem...... for just 20 seconds: freese. It took me a quarter to find out I hadn't connected the CS line to RAM1 (= pin14) but to pin 15, the one that goes to the two onboard 2114, 1024*4, SRAMs. Two SRAMs parallel to each other can cause problems. BUT THEN WHERE DID THAT EXTRA 1 KB OF RAM COME FROM ??? Then I saw my error and connected the CS line to RAM1: rubbish on the screen. I connected it to RAM2: again rubbish. Connected it to RAM3: nice screen, 4709 bytes free. Had to have dinner so I typed in and ran a little Basic program in the mean time. I started to use the AND gates and first added RAM2 and then RAM1. Worked out fine. But the above means that the order to add RAM is 3, 2, 1. Was that known? (not to me) -- Kind regards / Met vriendelijke groet, Ruud Baltissen www.Baltissen.org Message was sent through the cbm-hackers mailing listReceived on 2013-04-28 18:00:04
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