You should have only one position bridged for either 450 or 500 I believe(obviously different positions). Re-use the resistor or remove it and bridge with solder. The bus speed address circuit already has a pull-up(the small blue flat-pak by the jumper pads). My DP500 has been very stable at 550 since December. To go to 500, your processor board should look like the pictures of mine that Mike B. has from before the modification .
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