Using more than 32MB RAM quoted as limited to but wonder if 64MB RAM cards can be used.

If you think you know more than the manufacturer, go ahead & try it. I'm curious what your plans are for that old thing, you've been trying to upgrade for well over a year.
You're wondering if your 486 motherboard can use 64 meg simm sticks? Or are you talking about total installed ram? I doubt it could properly see a 64 meg stick. If you mean total ram, it wouldn't surprise me if it could see 128 meg--4 sticks of 32.
