You're sort of right. A lot of the IO is 1Mhz because of the cost saving on chips. But it switches to 1Mhz when you access those addresses. Basically accessing anything that needs 1Mhz drops the bus to 1Mhz. And that's both internal IO and external IO. So hanging something off of the 1Mhz per se doesn't change the clock but the moment you access the device it does. However the tube is not included in that so you get genuine 2Mhz.
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ninetydegrees
no subject
on 2009-08-14 08:43 am (UTC)