This table summarises the performance of Mac models (especially older models). For an explanation of these figures see the notes below the table. Some of the data is estimated, I apologise if any is inaccurate, contact me if you find any errors.
Here's the table...
CPU refers to central processing unit, the most important component of a computer. Apple used Motorola 680x0 processors for all Macs until they introduced the Power Macs which use the RISC PowerPC (PPC) processor jointly developed by IBM, Motorola and Apple. A * in this column means the CPU is the "cut down" version without a built-in FPU. Double processor machines have "x2" in this column.
FPU refers to floating point unit or maths co-processor. "int" means one is integrated into the main CPU, none means the machine has no FPU, floating point maths is performed by software instead. A * in this column means the FPU is optional, it is not supplied with every machine of this type.
MHz refers to the speed (in MegaHertz, or millions of cycles per second) of the main processor. If there is a * next to the speed it indicates the CPU runs at double the speed of the rest of the computer, therefore the full benefits of the CPU's speed are not gained. Multiple processor machines have the combined speed of the processors (eg a twin 1GHz machine is shown as 2000).
Bus refers to the width of the computer's bus. The bus is the set of "tracks" on the main circuit board that carries information to and from the CPU. The wider the bus is the more information can be moved at one time.
Speed is an approximate measure of the computer's CPU speed. Similar to MIPS but with a few extra factors thrown in to allow for other featyures. The basic "clock" speed of the CPU isn't a reliable measure of the computers real speed because different CPUs can do more or less in one cycle. For example a 68040 running at 32 MHz is far faster than a 68030 running at the same speed. Note that the speed of G4 computers is considerably greater than G3s but only if the AltiVec unit is used.
RAM is the maximum amount of RAM (Random Access Memory) that can be installed. Of course large amounts of memory are very expensive and few Mac users ever need there machines maximum capacity.
Disk refers to the approximate data transfer rate (in megabytes per second) for SCSI-based machines. A "F" here indicates the machine has Firewire (400 Mb/s) and "U" means USB (11 Mb/s).
Slots refers to the number of expansion slots in the machine. Expansion slots can be used to add extra hardware such as network, video and co-processor cards. If there is one it will be a PDS (processor direct slot). If there is more than one they will be Nubus slots.
Video indicates the built-in video capabilities of the machine. The first number is the bit-depth supported (32 means millions of colors, 16 thousands, 8 is 256 colors, 4 is 16 colors). The second number is the screen size this is supported for (14 is the standard 14 inch monitor at 640x480 resolution, 15 means a typical 15" 832x624 monitor, 17 means a 17" 1024x768 monitor). The code in brackets refers to the video hardware: 1 means ATI Rage (64), 2 means ATI Rage 128, 3 means NVidia GeForce, 4 means GeForce 4, 9600 means Radeon 9600.
A * next to the screen size indicates the smaller 640x400 resolution. Generally increasing the screen size decreases the number of colors available. B&W means the machine can only support black and white, if there is a ** next to this the computer can support color if you add a card.