A 256KB ROM Decoder + TOS Emulator for Atari ST and Mega ST
The SidecarTridge TOS 256KB Decoder is an add-on board for the Atari ST and Mega ST computers that, when paired with the SidecarTridge TOS emulator, allows you to run a wide range of TOS versions without swapping ROM chips. By decoding 256KB ROMs, it expands compatibility beyond the standard 192KB versions, enabling seamless use of TOS versions up to 2.06. The 256KB Decoder is soldered onto the Motorola 68000 CPU and works with a custom carrier board to deliver transparent decoding, making it ideal for Atari enthusiasts and developers interested in exploring various TOS versions on their systems.
The kit includes both the 256KB Decoder and the SidecarTridge TOS Emulator, providing everything you need to run a broad range of TOS versions on Atari ST and Mega ST computers. This powerful combination allows for seamless emulation of 192KB and 256KB ROM. To learn more about the SidecarTridge TOS Emulator and its full range of features, visit this page.
Why Choose the 256KB ROM Decoder + SidecarTridge TOS Emulator?
The 256KB ROM Decoder combined with the SidecarTridge TOS Emulator offers Atari ST and Mega ST users unparalleled flexibility and functionality. This integration allows access to a wide range of TOS versions, including those originally designed for later models like the Atari STe and Mega STe, without the need for physical ROM swaps. By emulating internal ROMs and decoding 256KB ROMs, users can seamlessly switch between different TOS versions and custom ROMs. This solution is ideal for enthusiasts and developers seeking to explore various operating systems and applications on their Atari ST or Mega ST computers.
How It Works
The 256KB ROM Decoder is an add-on board designed to enhance the functionality of the SidecarTridge TOS Emulator for Atari ST and Mega ST computers. By generating synthetic signals, this decoder enables the emulator to access the address ranges required for 256KB ROMs, which are standard in Atari STe and Mega STe models but not natively supported in earlier systems.
To enable Atari ST and Mega ST computers to utilize 256KB ROMs, the 256KB ROM Decoder performs the following functions:
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Address Signal Generation: The decoder synthesizes the necessary address signals corresponding to the $E00000 range, allowing the CPU to access the 256KB ROM space.
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Chip Enable (CE) Signal Creation: It generates a synthetic CE signal to activate the ROM only when the CPU accesses the designated address range, ensuring proper data retrieval.
These synthetic signals are then connected to the SidecarTridge TOS Emulator, enabling it to interface seamlessly with the 256KB ROMs.
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Before Purchasing Find Your Right Kit for your Atari ST
Before purchasing the 256KB Decoder, please note that it requires soldering onto the Motorola 68000 CPU. This task demands proficient soldering skills to ensure proper installation and functionality.
Additionally, it’s essential to select the appropriate kit based on your Atari ST or Mega ST motherboard model number. To determine your motherboard model, open the case and locate the model number printed on the board, usually in the middle bottom area. Refer to the Compatibility section for a list of supported motherboards.
| Kit | Supported Motherboards |
|---|---|
| STF and STFM Kit | 070789-001, C103175-001, C103414-001 |
| Mega ST Kit | C103544-001, C100167 |
For further requirements and detailed information, please consult the SidecarTridge TOS emulator documentation.
Frequently Asked Questions
I already own the SidecarTridge TOS Emulator. Can I purchase the 256KB Decoder separately?
No, the 256KB Decoder is not available as a standalone product. It is only sold as part of the SidecarTridge TOS Emulator kit, which includes a TOS Emulator board with an extra multiplexer and the 256KB Decoder.
If you already own the SidecarTridge TOS Emulator and wish to upgrade to the 256KB Decoder, you can purchase the complete kit at a discounted price. Please contact us for more information.
Can I use the 256KB Decoder with any Atari ST or Mega ST model?
The 256KB Decoder is compatible with specific Atari ST and Mega ST models. Please refer to the Compatibility section for a list of supported motherboards.
Do I need to solder the 256KB Decoder onto the Motorola 68000 CPU?
Yes, the 256KB Decoder must be soldered onto the Motorola 68000 CPU. This task requires proficient soldering skills to ensure proper installation and functionality.
Can I run custom ROMs with the 256KB Decoder and SidecarTridge TOS Emulator?
Yes, the 256KB Decoder and SidecarTridge TOS Emulator support custom ROMs, including EmuTOS—an open-source TOS replacement.
Are all TOS versions compatible with the 256KB Decoder?
While the 256KB Decoder supports all TOS versions up to 2.06, some versions are not compatible with Atari ST and Mega ST computers. Versions 1.06, 1.62, and 2.05 do not function on these models, even with the 256KB Decoder.
Can I switch between 192KB and 256KB ROMs with the 256KB Decoder?
Yes, the 256KB Decoder allows you to switch between 192KB and 256KB ROMs seamlessly. When paired with the SidecarTridge TOS Emulator, it provides transparent decoding for both ROM sizes.
Is there a version of the 256KB Decoder for computers with six ROM sockets?
While the 256KB Decoder is designed for computers with two (DUAL) and six (HEXA) ROM sockets, the online store currently offers only the DUAL version. The HEXA version needs extra components and more soldering points, making it more expensive. If you are interested in the HEXA version, please contact us for more information, but assume a 20% increase in price.
Are there any additional components required to use the 256KB Decoder?
The 256KB Decoder is designed to work with the SidecarTridge TOS Emulator and requires no additional components. The kit includes everything you need to run a wide range of TOS versions on your Atari ST or Mega ST computer.
Can I install the 256KB Decoder myself, or do I need professional assistance?
The 256KB Decoder requires soldering onto the Motorola 68000 CPU, which demands proficient soldering skills. If you are comfortable with soldering and have experience working with electronics, you can install the decoder yourself. However, if you are unsure or inexperienced, we recommend seeking professional assistance to ensure proper installation.
