QUESTION
        Will the MC68000 support 4 megabytes of DRAM using 1x9 1-Mbyte SIMMs?

        ANSWER

        You should have no problems interfacing standard DRAM SIMMs to the
        MC68000.Note that the MC68000 does not burst so you do not need any
        special type of DRAM such as page-mode DRAM which would normally be
        required to support bursting.

    Is this true?  Does this mean that I _can_ just use PC RAM with this
    type of MPU?  Does anyone know about or have any experience with this?

Sure, you CAN.  You'll need some sort of DRAM controller to at least
multiplex the address bus into the DRAM pins, unless you're using some 68k
variant that has a built-in DRAM controller.  How hard it is may depend on
how fast you want the system to go - if you clock the DRAM signals in based
on the 68k clock, you'll probably end up with a longer access cycle than
strictly necessary.  Using a separate clock gets you synchronization
issues, of course.  Some designs use delay lines here, I think.

The other thing that DRAM needs is periodic refresh - on low end systems,
you can use "software refresh".  Rather than complicating your memory
controller, you set up a periodic non-maskable interrupt to occur at the
refresh frequency, and then do a full columns worth of reads (ie 128
consecutive no-ops, assuming you put the right address lines in the right
place.)  Both the SUN-1 and cisco CSC/1 were 68k based processors that used
SW refresh.  IIRC, the original IBMPC used a periodic interrupt to start
an appropriately sized DMA (to nowhere) using the DMA controller.  Your
periodic interrupt routine can do more than no-ops, of course, as long
as it always reads something from every DRAM row...

BillW