CREATE TABLE table_3890 ("Model - Computer name" TEXT, "CPU type" TEXT, "No. of processors" TEXT, "Period of operation" TEXT, "Maximum peak performance  (  Teraflops  ) " TEXT, "Use" TEXT)

Name the use for amd opteron dual-core 2.6ghz
SELECT "Use" FROM table_3890 WHERE "CPU type" = 'AMD Opteron dual-core 2.6GHz'
SELECT "Use" FROM "table_3890" WHERE "CPU type" = 'AMD Opteron dual-core 2.6GHz'