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69 lines
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69 lines
5.5 KiB
Plaintext
---
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title: "The MonSTerBoard: Alt-RAM, IDE and Flashable TOS for the Mega ST"
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section: "retro"
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tags: "retro"
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description: "How the MonSTerBoard adds 8 MB of TT-RAM, dual IDE and flashable TOS to my Atari Mega ST 4 'High' workstation."
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layout: base.njk
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parent: "/retro/"
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---
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<h1>The MonSTerBoard: Alt-RAM, IDE and Flashable TOS for the Mega ST</h1>
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<div class="detail-content">
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<p>My <a href="/retro/atari-mega-st-fleet/">Mega ST 4 "High"</a> workstation is built around the MonSTerBoard, an upgrade board from Alan Hourihane that sits on the MegaBus and adds 8 MB of TT-RAM, dual IDE interfaces and a 2 MB flashable TOS to any Atari ST, STe, Mega ST or Mega STe, hence the name. It's the board that turns the "High" machine into a genuine multitasking workstation.</p>
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<h2>What the MonSTerBoard adds</h2>
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<ul>
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<li><strong>8 MB of TT-RAM</strong>, alternate memory usable with TOS 2.06, MiNT and MagiC. Configurable via the M_ALTRAM program, which then goes into the auto-start folder.</li>
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<li><strong>Dual IDE interfaces</strong>, two IDE connections on the board, ideal for a CompactFlash or IDE-SD adapter as mass storage.</li>
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<li><strong>Flashable TOS (2 MB)</strong>, a 2 MB flash chip that can hold up to four TOS images, so you can switch operating systems in software.</li>
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<li><strong>Optional real-time clock</strong>, a connector for an RTC module based on the Dallas DS1338 (already present on Mega ST/Mega STE mainboards).</li>
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<li><strong>512K EmuTOS and flash disk support</strong>, the spare flash space can even hold a fast boot disk or an EmuTOS image.</li>
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</ul>
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<p>The heart of the board is a Xilinx XC9572XL CPLD that ties it all together. For a Mega ST, the board needs a separate MegaBus adapter board, also available from Alan.</p>
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<h2>Installation</h2>
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<p>Installation is fairly straightforward. For a Mega ST, plug the MonSTerBoard together with the adapter onto the MegaBus, connect the power supply and run a cable to pin 10 of the ACSI port. One thing that catches people out: the original TOS ROMs on the mainboard must be removed, otherwise the machine keeps booting the old TOS instead of the one on the flash board.</p>
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<h2>The jumper block</h2>
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<p>The board has an 18-pin jumper block. The top row is 3.3V, the bottom row is GND, and combined with the middle row they set the options. From left to right: TOSSEL, FLASHSW, FLASHON, IDESW, SCL and SDA.</p>
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<ul>
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<li><strong>TOSSEL</strong>, for STFM/Mega ST with TOS 1.xx: jumper to GND boots from 0xE00000 (e.g. TOS 2.xx), jumper to 3.3V boots from 0xFC0000 (e.g. TOS 1.xx).</li>
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<li><strong>FLASHSW</strong>, swaps the second 1 MB of the flash chip between the 0xE00000 and 0xFC0000 windows, so you can flash the other operating system.</li>
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<li><strong>FLASHON</strong>, disables access to the flash for recovery mode, so the original ROMs can be reinstalled if needed.</li>
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<li><strong>IDESW</strong>, swaps the first and second IDE interfaces.</li>
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<li><strong>SCL/SDA</strong>, connection for the RTC module.</li>
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</ul>
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<h2>Software</h2>
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<p>Alan provides three programs for the MonSTerBoard: M_FLASH.ZIP to write the onboard flash, M_ALTRAM.ZIP to configure the RAM (2, 4, 6 or 8 MB, then placed in the auto-start folder), and M_RTC.ZIP for the Dallas RTC module. In total you can install four TOS versions: two 192 KB and two 256 KB images.</p>
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<h2>TOS selection via the jumpers</h2>
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<p>The TOSSEL and FLASHSW jumpers pick which TOS the machine boots from the flash. A common setup maps them like this:</p>
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<table>
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<tr><th>TOSSEL</th><th>FLASHSW</th><th>Boots</th></tr>
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<tr><td>off</td><td>off</td><td>EmuTOS</td></tr>
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<tr><td>on</td><td>off</td><td>PP's modified TOS 1.04</td></tr>
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<tr><td>off</td><td>on</td><td>TOS 2.06</td></tr>
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<tr><td>on</td><td>on</td><td>Kaos TOS 1.4.3</td></tr>
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</table>
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<p>The MonSTerBoard is generally blitter-agnostic and works with all common Mega ST blitter variants, as long as the bus signals are clean. Common symptoms like a white screen with no boot are, in practice, usually caused by contact issues at sockets or incorrect jumper settings, not a defective blitter.</p>
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<h2>My Setup</h2>
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<p>In my Mega ST 4 "High" machine the MonSTerBoard provides the 8 MB of TT-RAM that TOS 2.06 and Geneva use for real multitasking. For storage I use the dual IDE interface, booting the system directly from a CompactFlash card. I started with a 4 GB card, but that didn't work reliably, so I switched to a 1 GB card, which works fine. There's no ACSI hard drive connected in this machine; the IDE boot is noticeably faster than an ACSI drive would be. Combined with the <a href="/retro/et4000-experiment/">ET4000 graphics card</a> and its dedicated monitor, it's the most capable machine in the fleet.</p>
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<h2>Gallery</h2>
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<img src="monster-ide.jpg" alt="MonSTerBoard IDE adapter with CompactFlash card" width="640" height="480">
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<p class="caption">The MonSTerBoard IDE adapter with a CompactFlash card attached.</p>
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<img src="monster-1gb.jpg" alt="MonSTerBoard with the 1 GB CompactFlash card" width="640" height="480">
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<p class="caption">After the 4 GB card didn't work, I switched to a 1 GB CompactFlash card.</p>
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<img src="monster-pins.jpg" alt="MonSTerBoard pins and jumper block" width="640" height="480">
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<p class="caption">The MonSTerBoard pins and jumper block.</p>
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<h2>Sources</h2>
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<ul>
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<li><a href="https://www.jungsi.de/monster-atari-st/" target="_blank">MonSTer [Atari ST] - Jungsi's Corner (installation guide)</a></li>
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<li><a href="https://www.atarikit.co.uk/monster/monster.html" target="_blank">MonSTer order form - AtariKit (official page)</a></li>
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</ul>
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</div>
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