I have an MSI 486DX2-66 motherboard which I would like to upgrade using a Cyrix DX4-100 processor. No manual but the board is beautifully marked. Of the many settings shown there are two that could apply. One says " 486DCI, DX2, DX4". The other "CYRIX M7. The MSI support group say they no longer have the manual either. Can anyone tell me which setting to use. The m.b. number is MS4137. Many tks.