This is the fourth BIOS for the IBM 5160 (the revisions are: 08/16/82, 11/08/82, 01/10/86, 05/09/86)
It is dated 09MAY86 (05/09/86).

U18 has the IBM part number of 59X7268 or 62X0890 (see Note 1), and is 32K in size
U19 has the IBM part number of 62X0819 or 68X4370 (see Note 1), and is 32K in size

8 bit checksum of 59X7268/62X0890 = 19
8 bit checksum of 62X0819/68X4370 = E7
                                   ----
                            added = 00


There are two BIN files in this ZIP file:
1. BIOS_5160_09MAY86_U18_59X7268_62X0890_27256_F800.BIN  --> Use this to create a U18 using a 27256 EPROM (rated at 250nS or faster)
2. BIOS_5160_09MAY86_U19_62X0819_68X4370_27256_F000.BIN  --> Use this to create a U19 using a 27256 EPROM (rated at 250nS or faster)



NOTE 1: These differently marked chips have identical contents.
        62X0890/68X4370 are PROMS whereas 59X7268/62X0819 are EPROMs.
        An inspection of the contents of U19 reveals the string, "62X0819=68X4370 59X7268=62X0890".