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Apple Computing Products:
macOS - Operating System
Boot Choices - Mojave or Mountain Lion
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<blockquote data-quote="Rich M" data-source="post: 1878671" data-attributes="member: 407377"><p>Both boot drives are mounted. It is a single 480 GB SSD, partitioned into two drives. When I am running Mojave, I see them both.</p><p></p><p>I tried setting the start-up drive to the old OS (Mountain Lion). I <em><strong>think</strong></em> the computer booted, but I'm not sure. I heard the musical chord that plays when a MAC boots. However, <strong><em>NOTHING</em></strong> appeared on the monitors (dual monitors). They remained black. No desktop. The only way I can see anything in Mountain Lion is to remove the Sapphire RX580 video card and install the old ATI Radeon video card. Then the computer will boot into Mountain Lion normally and both monitors display properly.</p><p></p><p>However, now I have a huge new problem. When running Mountain Lion, if I go into System preferences and choose Start Up Drive, <strong>the Mojave boot drive does not appear! </strong>If I run the Disk Utility app, the Mojave drive shows as an unmounted partition named "diskOs2" and I cannot mount it.</p><p></p><p>I am posting this while running Mountain Lion. I don't see a way to boot back into Mojave! Now I am <strong><em>really </em></strong>dead in the water.</p></blockquote><p></p>
[QUOTE="Rich M, post: 1878671, member: 407377"] Both boot drives are mounted. It is a single 480 GB SSD, partitioned into two drives. When I am running Mojave, I see them both. I tried setting the start-up drive to the old OS (Mountain Lion). I [I][B]think[/B][/I] the computer booted, but I'm not sure. I heard the musical chord that plays when a MAC boots. However, [B][I]NOTHING[/I][/B] appeared on the monitors (dual monitors). They remained black. No desktop. The only way I can see anything in Mountain Lion is to remove the Sapphire RX580 video card and install the old ATI Radeon video card. Then the computer will boot into Mountain Lion normally and both monitors display properly. However, now I have a huge new problem. When running Mountain Lion, if I go into System preferences and choose Start Up Drive, [B]the Mojave boot drive does not appear! [/B]If I run the Disk Utility app, the Mojave drive shows as an unmounted partition named "diskOs2" and I cannot mount it. I am posting this while running Mountain Lion. I don't see a way to boot back into Mojave! Now I am [B][I]really [/I][/B]dead in the water. [/QUOTE]
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Apple Computing Products:
macOS - Operating System
Boot Choices - Mojave or Mountain Lion
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