What are the best settings for Xeon processors? I'm running 2x 2.66 GHz Xeon's and getting pretty low chains per day:
{
    "blocks" : 157519,
    "chainspermin" : 10,
    "chainsperday" : 1.18470870,
    "currentblocksize" : 1000,
    "currentblocktx" : 0,
    "difficulty" : 9.86931497,
    "errors" : "",
    "generate" : true,
    "genproclimit" : -1,
    "primespersec" : 1754,
    "pooledtx" : 0,
    "sieveextensions" : 6,
    "sievepercentage" : 10,
    "sievesize" : 1000000,
    "testnet" : false
}

Changing sievesize doesn't seem to do much.