Document ID: TOS-HW-REF-M02 Revision: 1.0 Author: ThisOldScot
Section_1: Overview#
The Neo Geo AES utilises a proprietary BIOS ROM that restricts the user to a specific region and limits access to debug menus. In the Borders Workshop, we utilise the Universe BIOS (UniBIOS) by Razoola to unlock the full potential of the hardware.
This guide covers the logic-level extraction of the original 40-pin MASK ROM and the installation of a high-quality socket to enable future firmware swaps.
Section_2: Tools & Materials Required#
| Item | Spec | Purpose |
|---|---|---|
| Desoldering Pump | Engineer SS-02 | Clearing 40 high-thermal-mass vias. |
| IC Socket | 40-Pin Machined | Ensuring reliable pin contact. |
| EPROM | M27C1024 or equivalent | The target hardware for the UniBIOS code. |
| Low-Melt Solder | Thermal Bridge | Assisting in the extraction of the 30-year-old IC. |
| Amtech NC-559 | Tacky Gel Flux | Managing heat across the 40-pin bus. |
Section_3: The Extraction Protocol#
STAGE_3: 01 // Localising the BIOS#
Locate the BIOS IC (usually designated as IC-B1 or similar) on the AES motherboard. It is a large 40-pin DIP chip near the cartridge slot.
STAGE_3: 02 // The “Flood” Technique#
Vintage SNK boards use extremely high-quality, high-thermal-mass ground planes.
- Apply tacky flux to all 40 pins.
- Add fresh leaded solder to every joint. This mixes with the original lead-free/oxidised solder to lower the overall melting point.
STAGE_3: 03 // Vacuum Extraction#
- Use the Desoldering Pump to clear each via.
- The Logic: You must be able to “wiggle” every pin with a pair of tweezers. If a pin is still held by a microscopic bridge of solder, do not force the chip. Repeat the heating cycle.
STAGE_3: 04 // Socket Installation#
- Clean the vias with 99.9% IPA.
- Install a Machined-Pin Socket. These are superior to “Leaf-spring” sockets as they offer better vibration resistance and do not oxidise as quickly.
- Solder the corners first to ensure the socket is flush against the substrate.
Section_4: Logical Verification: The Handshake#
Before inserting the UniBIOS EPROM:
- Use a Multimeter to check the +5V Rail on Pin 40 and Ground on Pin 20.
- Verify there are no solder bridges between adjacent Address or Data lines using Continuity Mode.
Section_5: Technical Warning#
Safety_Warning
PINOUT ALERT: Be advised that some early AES revisions use a BIOS with a non-standard JEDEC pinout. While the UniBIOS is compatible, always cross-reference your board revision (e.g., NEO-AES3-6) with the UniBIOS documentation to ensure you do not need to perform any “Pin-Swapping” jumpers.
Section_6: Practical Application: Restoring Arcade Authority#
Installing a UniBIOS allows the Borders Workshop to:
- Toggle AES/MVS Mode: Enabling arcade-specific features.
- Cheat Engine Access: Useful for testing hardware stability under high sprite-count stress.
- Hardware Test Suite: Integrated logic checks for the 68000 CPU and Z80 sound controller.