

This is one of a few revisions of motherboard BIOS for the IBM 5160 (IBM XT).
This revision is dated 09MAY86 (05/09/86).


+---------------------------------+
|  GENERAL                        |
+---------------------------------+

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


+---------------------------------+
|  FILES                          |
+---------------------------------+

File BIOS_5160_09MAY86_U18_59X7268_62X0890_27256_F800.BIN is a binary image of ROM chip U18.  [ 32 KB in size ]
File BIOS_5160_09MAY86_U19_62X0819_68X4370_27256_F000.BIN is a binary image of ROM chip U19.  [ 32 KB in size ]


+---------------------------------+
|  USING FILES TO MAKE EPROMS     |
+---------------------------------+

1. Obtain two blank 27256, or 27C256, EPROMs rated at 250 ns (or less [faster]).
   Avoid the NEC PD27C256, an EPROM known not to work on early 5160 motherboards (where ROM sockets have pins 1 and 27 tied).

2. Burn file BIOS_5160_09MAY86_U18_59X7268_62X0890_27256_F800.BIN to the first 27256, then label the 27356 as "U18".

3. Burn file BIOS_5160_09MAY86_U19_62X0819_68X4370_27256_F000.BIN to the second 27256, then label the 27356 as "U19".


+---------------------------------+
|  NOTES                          |
+---------------------------------+

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".



