So I now have one stick of 512m 2700 ram and the rest is PC133 making up 1.5gig. Works fine so far.
I'm puzzled. AFAIK, PC133 RAM is typically a 168-pin SIMM while the PC-2100 or PC-2700 found in the MDD are 184-pin.
So I'm not sure how you can have the PC-133 installed and working…?
The PC-133 was common in the Quicksilvers with their 133MHz data bus.
The MDD's have either a 133MHz bus in the 867MHz and 1.0GHz machines or a 167MHz bus in the faster ones.
So, your (either) single or dual 1.25MHz machine wants PC-2700.
* You can also use PC-3200. It will work fine though it will run at PC-2700 speed.
The optimum config for the MDD is four 512Mb PC-2700 SIMMS.