Apple made quite a few departures from the way things were done on previous machines, the most obvious of which was the use of the PPC processor vice the 68000 family of processors. Other things include the external video connector, called HDI-45, which only appears on these early Power Macintosh models. Also there is an AAUI ethernet connector, as well as the standard SCSI, dual serial, single ADB, sound in, and sound out. The built-in video of the 6100 uses 640k of the system RAM for it's video RAM, allowing a maximum of 832x624 at 8bits, or 640x480 at 16bits. Unlike other models that can expand the VRAM using special memory modules, the VRAM for the onboard video cannot be expanded. There are three drive bays, the right-most of which is used for the floppy drive, while the left-most bay is used for the hard disk. The center bay, which is the only 5-1/4" bay, is generally used for a CD-ROM.
Internally, there are two 72pin SIMM sockets for memory expansion, a cache SIMM socket and a ROM SIMM socket. The cache and ROM SIMM sockets are very close to each other and are interchangeable. There is also a PDS connector, though this connector is incompatible with the earlier PDS connector as used on the LC-series and Performa 6200 and 6300. Due to the low profile design of the case, any card plugged into this connector will need a right-angle adaptor. There is 8MB of RAM soldered directly to the mainboard near the two RAM SIMM sockets.
Some of the things that could be done to expand the 6100 include the use of PDS or, using an adapter, NUBUS video cards, which removed the restraints placed upon the system by the built-in video. RAM can be expanded up to 264MB, though Apple states the maximum for this machine is 72MB. This is due to the fact that neither 64MB or 128MB 72pin SIMMs were available at the time of it's introduction. Newer Technology also produced a G3 upgrade board for this machine, which allowed a maximum clock speed of 330mhz, based on the system bus speed of 33mhz. Sonnet Technologies also produced G3 upgrade boards, as well as boards based on the G4 cpu of up to 300 mhz. These CPU upgrades actually plug into the PDS socket.
This particular 6100 has a Sonnect Crescendo G3 upgrade installed in the PDS slot, clocked at 231mhz with a 33mhz system bus. The Crescendo G3 upgrades determine on their own the maximum speed of the CPU and set's itself accordingly. The system also has an 8x CD-ROM, 1 gig hard disk, 40 meg of RAM, and operates under System 7.5.3. I also have a Radius PrecisionColor 24x accelerated video board, but since it uses the NUBUS interface it is incompatible with the Crescendo G3 upgrade. The Crescendo provides it's own PDS pass-thru connector and is compatible with the Apple AV video board. The PrecisionColor includes 3meg of VRAM and is capable of 24bit color at a maximum resolution of 1152 x 882. The PrecisionColor would be used with a righ-angle PDS-to-NUBUS adapter for use in the 6100.