You have already listed the best software to do this but there is also Atanua which is pretty basic if not a bit limited: http://sol.gfxile.net/atanua/index.html
I'd probably persevere with Proteus, it gives you a good grounding with digital logic and has an extensive IC library. There's loads of tutorials on Youtube if you are stuck.
There's a lot of good digital logic primers out there too. You will probably want to get some of that under your belt before diving into DRAM controllers.
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Re: simulation of a digital circuit
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