I have had a lot of luck in getting 640k on my XT Clone, the Sanyo MBC-775.

I went to the Vintage Computer Festival Southwest, and I got one of the biggest prizes that anyone could ever ask for when it comes to an XT computer:

An AST SixPak!

I was so happy when I found this. Now I not only have the full 640k that I was looking for (I wish it could be used on the motherboard), but I can use a mouse too, and I have a clock/date system!

To try to get my Sanyo further in its capabilities (At least to try to run Commander Keen 4), I decided to get a 10MHz V20 CPU. Unfortunately, it has not been easy.

I have not been able to use the turbo capability unmodified on either the original 8088-2 CPU or the V20. I get instability, errors (bad enough on 4D Sport Boxing that it can't even start), and corrupted graphics.

There's a jumper that halves the clock speed, but thankfully, using it with the turbo mode enabled allowed me to turn up the speed enough to at least have Commander Keen playable and enjoyable. (I don't mind the choppiness. I just want to not be waiting half-a-second for each frame to load.)

I'm not looking for Wolf-3D quality, but I would like to have nice late-80s early-90s motion (and as best sound it can do with its PC speaker), rather than forcing the computer to hobble on.