Someone made a similar turbo years ago, though I never understood why they changed the cia clock speed too. Ok is there the magic? C64 mobo can run at 4Mhz speed. If you force CPU to run at 2Mhz and move his clock to position which does not interfere with VIC acccess to memory, you will get TDC. It take some time to fix problem with access to VIC and SID registers but... it works. The story of 4Mhz is like c128 in c64 mode. You have colour random squares on the screen if you force CPU to run at 4Mhz so I've decided to force CPU to run at 2 Mhz at bad line, 3 Mhz at long/normal line, and 4 Mhz on borders. CPU power at 4Mhz mode is about 3.5 faster as is in 1Mhz mode. I found benchmark on internet (some FP calculations in BASIC) so 1Mhz takes 1m41s and 4Mhz mode takes 29s. Knowing side effects: - TDC(d1) doesn't work with 1541U at 2/4Mhz speed, - in 4Mhz mode you can't change $01, because this register is attached to 6502 core and it's very slow (it work's at 2Mhz and propobly at 3Mhz) - old cards like AR, MMCReplay, FC3 dosn't work in 2/4Mhz mode. - old cards like BlackBox or FC2 (and rest with one EPROM and one TTL) works in 2Mhz mode. - timers of CIA are conected to CPU clock and they running faster. https://csdb.dk/release/?id=102360 https://web.archive.org/web/20180925055138/http://wiki.projekt64.filety.pl/doku.php?do=show&id=projekt64/turbo https://csdb.dk/release/download.php?id=196745 https://csdb.dk/release/download.php?id=196744 On 22/06/2022 20:24, tokafondo_at_tokafondo.name wrote: > Do you think the chip select outputs of the PLA could be used in such a way??? >Received on 2022-06-23 09:00:08
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