Mac OS X Developer Preview 1

Mac OS X Developer Preview 1 is the first Developer Preview of Mac OS X Public Beta. This build still included the Platinum theme, which would be replaced with the Aqua theme later in Developer Preview 3. Unlike the later Developer Previews, it is still similar to Mac OS X Server 1.x and the installation media boots to a Mac OS 8.6 pre-installation environment instead of instantly booting to setup. It was introduced at the Worldwide Developers Conference in 1999, showcasing the Darwin kernel to Mac OS and the bases for the completed operating system.

The xnu build for Beaker1N5 is Mac OS Version 10.0: Fri Apr 30 23:26:14 PDT 1999; root(rcbuilder):Objects/xnu-24.6.obj~2/RELEASE_PPC powerpc

System requirements
According to the installation documentary, this developer preview requires the following: This version of Mac OS X works with Power Macintosh G3 computers ("beige" desktops and "blue and white" tower) with:
 * At least 64 MB of RAM
 * Internal video, or an Apple-supplied ixMicro or ATI video card
 * A hard disk with at least 1 gigabyte (GB) of available space