PowerExpress Manhattan Prototype
PowerExpress Manhattan was to be the next evolution of the Power Macintosh desktop line, due to replace the Power Mac 7300 with the new PowerExpress architecture.
In 1996 when Apple was working on the PowerExpress project, it was planned to be based on two motherboard configurations. PowerExpress was the more widely known, 6 PCI slot tower board. PowerExpress Manhattan was virtually unknown, as a 3 slot version of PowerExpress, designed to be put in desktop and mini-tower configurations. Though it is not known when Apple killed the PowerExpress Manhattan design, it is very similar to the Gossamer (Beige G3) board design, and the Power Macintosh G3 (Beige) Series got its start from it.
The PowerExpress was supposed to be a melding of technologies, blending the best features of the 8600/9600 series (processor card upgradability, 6 PCI cards on the PowerExpress tower) and next generation systems (SDRAM, G3 optimizations, upgraded DAV capabilities). With a quick glance and untrained eye, the PowerExpress Manhattan motherboard looks virtually identical to that of a Power Mac 7300/7500/7600. The main difference that sets it apart is the new DAV slot, located behind the top PCI card slot. The slot itself is labeled "VCI" likely meaning "Video Component Interface" (similar to Peripheral Component Interface, or PCI), and would have provided additional bandwidth for faster and better video cards to be used.
PowerExpress Manhattan contains many unique chipsets not found on production Macs. Some, like Heathrow, Denali, and Screamer, were used on other Macs such as the Power Mac 9600, where as other ones, such as Radical, Nine99, Kaos, Fatman, Little Boy, and 53C860 are native to the PowerExpress Manhattan board. It is also obvious that Manhattan, Fatman, and Little Boy are all references to the Manhattan Project, the United States Nuclear Weapons program, which took place during the 1940's. (Fatman and Little Boy were the names of the two atomic bombs dropped on Japan in 1945)
Though I have yet to be able to get PowerExpress Manhattan to boot successfully, it does have an altered Chimes of Doom. Thanks to the help of fellow 68KMLA member and AppleFritter contributer jt, we have also been able to obtain the boot chime of a PowerExpress tower, which likely is also on the PowerExpress Manhattan.