If computer speed were determined by processor speed alone, comparisons among machines would be far simpler.

But a computer does more than process a simple stream of information.  It must contend with an assortment of input and output devices, such as networks and displays, and pass that data to and from memory on behalf of each.  Because of this, performance hinges as much on a computer's total design as on the speed of its individual components.

The best measure of performance is "throughput," the amount of information that can be processed through the computer in a mere second.  How well a computer performs this measurement is determined by its architecture: the core design around which the computer is engineered.

Desktop computers offer a variety of architectures, from the most basic PC's to the most advanced workstations.  At the high end throughput is noticeably superior.  But even an expensive workstation can bog down when too many devices try to access memory at once.  If the network, printer, display, storage and other devices must queue up for access, performance can only be diminished.

The NeXT Computer acknowledges that throughput is absolutely key to performance. For that reason, we chose not to use the architecture of any existing desktop computer. The desired performance could be found only in a computer of a different class: the mainframe.

Having long shed any self-consciousness about such mundane matters as size and expense, mainframes easily dwarf desktop computers in the measure of throughput.

This is accomplished by a different kind of architecture.  Rather than require the attention of the main processor for every task, the mainframe has a legion of separate Input/Output processors, each with a direct channel to memory.  It's a scheme that works with ruthless efficiency.

The problem for NeXT, then, was not in finding the proper type of architecture. It was in reducing its bulk so it could sit upon a desk without crushing it - and in making its power more affordable.

The solution was Very Large Scale Integration (VLSI). This technology allowed the shrinking of mainframe architecture, with great economy, on two chips. One contains 12 Input/Output processors, each with direct access to memory; the other contains the circuitry to manage the mass storage.

This unprecedented desktop architecture allows the NeXT Computer to outperform the fastest PC's and many advanced workstations. In the vital measurement of throughput, NeXT technology actually comes within striking distance of a mainframe.

In addition, this drastic reduction in size allowed NeXT to contain the entire system on a single board (pictured to your right).  Measuring 11 inches square, it incorporates three processors from Motorola: a 68030 central processing unit, a floating-point unit and - standard for the first time in a desktop computer - a digital signal processing chip capable of producing CD-quality sound.  All three operate at 25 MHz.  The system board is shipped with eight megabytes of memory, and is expandable to 16 megabytes using 1 MB Single Inline Memory Modules (SIMM'S).

On one edge of the board you'll notice the ports that link the NeXT Computer to the outside world, and to other devices as well.  The MegaPixel Display and NeXT 400 dpi Laser Printer are both connected here.  A SCSI port, with Macintosh-compatible pinout, allows the addition of various SCSI devices, such as hard disk or scanner.  There are two RS422 serial ports, which are also Macintosh-compatible, and a thin Ethernet connector (to make use of the full 32-bit Ethernet hardware built onto the board).  There is also a special port that allows for direct communication with the digital signal processing chip.

The entire board consists of only 45 integrated circuits.  It is manufactured to microscopic tolerances in a roboticized factory in Fremont, California - a factory designed and built entirely by NeXT.  Reducing the number of parts on the circuit board results in greater economy.  But even more important, this design enhances both reliability and ease of servicing.

The system board resides in one of four slots inside the computer.  The other three, though empty, represent an important commitment by NeXT: Our architecture is wide open for development by the entire computer industry.  In the future, you'll be able to add new features, from gigabytes of memory to co-processing capabilities, simply by plugging in an expansion board.