ATI VGA Wonder‑16 Rev 2 – BIOS Archive (Version 3.1.02)
========================================================

Overview
--------
This archive contains the reconstructed VGA BIOS from an ATI VGA Wonder‑16
Revision 2 graphics card (circa 1988). The BIOS is implemented using two
UV‑erasable 27C256 EPROMs, each 32 KiB in size. Together they form a
single 64 KiB VGA Option ROM image. The EPROMs store the BIOS in
EVEN/ODD interleaved byte format, which is typical for early multi‑chip
ATI VGA and SuperVGA designs.

Both ROMs were individually dumped, verified, and then recombined to
produce a correct 64 KiB VGA BIOS suitable for archival, analysis, or
emulator use.

File Inventory
--------------
1) BIOS_V3-1.02_EVEN.bin
   Size:    32768 bytes
   SHA-256: 7e618ce60099be9639cfb2e619c283f177a9ee6f8dca44e64e49b3465c209553
   Notes:   Contains the EVEN (low) bytes of the BIOS.

2) BIOS_V3-1.02_ODD.bin
   Size:    32768 bytes
   SHA-256: 94abb5dbe5925ffbe6b98dff991816982a641bb1facf9b2c504affa1e2f05086
   Notes:   Contains the ODD (high) bytes of the BIOS.

3) BIOS_V3-1.02_FULL.bin
   Size:    65536 bytes
   SHA-256: b77aff6246bbb50aa26915cb87b9fb9053678854774b5cde8c41c64ab945fbf7
   Notes:   Fully reconstructed 64 KiB BIOS created by interleaving:
               byte0 = EVEN[0]
               byte1 = ODD[0]
               byte2 = EVEN[1]
               byte3 = ODD[1]
            The resulting image begins with the correct VGA signature:
               55 AA
            and contains valid ATI BIOS structures and revision data.

BIOS Details
------------
BIOS Version:     3.1.02
BIOS Date String: "1988/11/11 17:11" (visible at offset 0x8050 in full ROM)
Signature:        VGA Option ROM header begins at offset 0x8000 in the chip,
                  producing a standard 55 AA header once interleaved.

Layout:           A single 64 KiB VGA BIOS mapped by the ISA ROM decoder
                  at C000:0000 in typical VGA fashion.

Purpose:          Provides VGA core routines, ATI extended mode tables,
                  Wonder‑16 specific features, and configuration support.

Interleaving Notes
------------------
The ATI VGA Wonder‑16 Rev 2 employs a 16‑bit ROM data bus. The EPROMs
store alternating bytes of the BIOS:

   EVEN chip -> addresses 0x00000, 0x00002, 0x00004, ...
   ODD  chip -> addresses 0x00001, 0x00003, 0x00005, ...

This is why neither chip individually contains a valid VGA header, but
the combined image does. No address shifts or padding correction were
required—both ROMs begin usable data at offset 0x4000, producing a
continuous 64 KiB image after combination.

Preservation Notes
------------------
- These EPROMs are 27C256 and do *not* support electronic JEDEC ID
  reads. Tools like minipro must be invoked with "-y" to bypass ID
  checking.
- Both original dumps exhibit consistent padding in their upper halves,
  confirming correct readout and matching the expected physical layout.
- The reconstructed BIOS checksum matches ATI conventions for the era.

Reflashing Guidance
-------------------
If restoring the BIOS on physical hardware:

1) Program BIOS_V3-1.02_EVEN.bin into a blank 27C256 EPROM
   and install in the EVEN-byte socket.

2) Program BIOS_V3-1.02_ODD.bin into a blank 27C256 EPROM
   and install in the ODD-byte socket.

3) Ensure both EPROMs are securely seated and oriented correctly
   (notch matching the silkscreen).

End of File
