

This is one of a few revisions of motherboard BIOS for the IBM 5170 (IBM AT).
This revision is dated 15NOV85 (11/15/85).
It is found in type 3 motherboards (type 3 runs at 8 MHz).


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

ROM chip U27 has the IBM part number of 61X9266, and is 32K in size
ROM chip U47 has the IBM part number of 61X9265, and is 32K in size


8 bit checksum of 61X9266 = 10
8 bit checksum of 61X9265 = F0
                           ----
                    added = 00


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

File BIOS_5170_15NOV85_U27_61X9266_27256.BIN is a binary image of ROM chip U27.  [ 32 KB in size ]
File BIOS_5170_15NOV85_U47_61X9265_27256.BIN is a binary image of ROM chip U47.  [ 32 KB in size ]


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

1. Obtain two blank 27256, or 27C256.
   - 6 MHz 5170 motherboard: Ones rated at a maximum access time of 260 ns. (Or less, e.g. 250 ns.)
   - 8 MHz 5170 motherboard: Ones rated at a maximum access time of 190 ns. (Or less, e.g. 150 ns.)

2. Burn file BIOS_5170_15NOV85_U27_61X9266_27256.BIN to the first 27256/27C256, then label the 27256/27C256 as "U27".

3. Burn file BIOS_5170_15NOV85_U47_61X9265_27256.BIN to the second 27256/27C256, then label the 27256/27C256 as "U47".





