Power Macintosh 6500
Introduced in February 1997, the Power Macintosh 6500 replaced the earlier Power Macintosh 6400. It was powered by either a 225 or 250MHz PowerPC 603e, and included an internal Iomega Zip drive. All other specs are the same as the Power Macintosh 5500. The 225MHz configuration didn't include the video input/output circuitry and sold for $1,799. The 250MHz model sold for $2,099. A 300MHz model was announced in the spring (along with a 275MHz model) and was the first computer, Mac or PC, to break the 300MHz clock speed barrier.
The RAM expansion slots accept the 8-byte DIMM (dual inline memory module). As its name implies, the 8-byte DIMM has a 64-bit-wide data bus. The DIMM slot accommodates 168-pin 5-volt fast-paged and EDO DRAM DIMMs.
The main logic board has a slot for a second-level (L2) cache on a DIMM. The L2 cache DIMM contains the cache controller, tag, and data store memory. It is a lookaside cache, which is connected to the PowerPC 50 MHz processor bus.
The main logic board uses the industry-standard peripheral component interconnect (PCI) bus for an I/O expansion bus. The PCI bus is a 32-bit multiplexed address and data bus. The PCI expansion slot has a 33.33 MHz system clock. PCI I/O expansion cards are mounted horizontally in a 90-degree straight-through adapter board, which is installed in the PCI expansion slot on the main logic board. A total of 15 watts of power is provided for each of the PCI expansion slots. Both 5 volts and 3.3 volts are supplied; the total power consumed by both voltages must not exceed the 15-watt maximum. The main logic board requires that PCI cards use the 5-volts signaling standard described in the PCI Local Bus Specification, Revision 2.0.
QuickDraw 3D Acceleration and Video Memory
The logic board provides 2 MB of video memory for support of display modes up to 1152 by 870 at 16 bits of resolution. The largest supported display size is useful for standard 2D applications. For 3D applications, the 2 MB of video memory space is used differently, which restricts the useful display size and supported bit depth. For example, QuickDraw 3D utilizes double buffering if the hardware supports it. Double buffering immediately reduces the available video memory for application use. In addition, 3D applications that use a Z buffer for hidden texture removal have even less space available for caching textures to increase graphics rendering speed. To get the most performance out of 3D applications in the 2 MB of video memory, the display mode size should be reduced. A 512-by-384 display mode is provided specifically for increasing the available memory space for texture caching to improve 3D graphics rendering speed.