The DP83826 has extended registers than can help improve the margins for 10BaseTe TP_IDL tests.
Register 0x0023 = H8 by Default
Setting the Register to H9 or HA can improve Margins.
See Pictures below (TP_IDL Load2)
| 0x0023 = H8 |  |
| 0x0023 = H9 |  |
| 0x0023 = HA |  |