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for fx-unit-yuki they did use /CEO. I tried removing /CEO and used /ASEL twice as input as you suggested but no success. I wonder if its maybe my rom preparation? I swap binned before splitting into 2 parts. I also tried splitting before swapbin, but no luck, only black screen. On my umkt aliexpress...

I tried this schematic using LS00 NAND gates. It does work when its only a single 4mb game. I only get garbage marble when I try to start a 2x4mb game. Any idea what I need to adjust to have it working with 2x 4mb game? I know the rom is good, since I tested into an aliexpress umkt board. Its a chea...

I found this 8mb cartridge , it's simply using nand gates
https://www.retrorgb.com/fx-unit-yuki-p ... drive.html

A combinaison of /ce0, /asel and a22.

Wondering if someone have this schematic?

Is it better to use these signals instead of /as to create the roms /ce?

Thank for replying,
I'll definitely give it a try.
It I understood, I cannot put any graphical contents in region $800000-9fffff?

Was wondering if umkt would work with this schematic?

I will definetly share but I must find more information about /ce for third rom and dma for the $800000 - $9fffff region.

There is no reply, so cannot do a lot.

/DTACK is an open drain input, which means you never want to actively drive it high, only low. The 139 actively drives its outputs regardless of whether they are low (active) or high (inactive) which is bad. Thanks for this reminder, since its an open drain input it needs to be floating when its no...

I’d like to build myself a custom Genesis board. I already built a 4MB board with onboard 32K SRAM and it works great. Using 74HC74 and 74HC139, I’ve asserted ROM-CE and RAM-CE using /CE_O, /VRES, /TIME, D0, A21. /CART is tied to ground. /CAS_0 is used as /OE for both ROM and RAM I’m using /LWR on R...