Atari 800 Computer System












Part 2: More than meets the eye.


The Atari 800 expansion bays were originally meant for just an OS "Personality Card" and up to 3 16K Memory modules to give the computer system a total of 48K which for a computer system in 1979, was a very large amount of memory.   Also the CPU of the the system, the 8-bit 6502 processor was capable of a total of 64K of linear memory, so giving the system 48K was an admiral amount of memory for this budding new computer system.


 However some interesting things were hidden in those expansion bays.  Capabilities that even the very engineers who designed it never saw possible at the time. However just as programmers had unlocked numerous unknown capabilities to make the little Atari 2600 VCS do magical and wonderful graphics that were never thought even remotely possible when it was designed, so too were some magical secrets and powerful capabilities just waiting to be unlocked within the Atari 800.


Companies such as Axlon, Mosiac, Intec, Newell, BIT-3, Austin Frankin, CMC and many others would develop and sell an assortment of OS boards, memory upgrade boards, RAMdisk boards (the very first SSD drives), Video boards and Parallel/Serial boards.


Even today on the Internet's most active Atari community:  there are dozens of independent and small group hardware hackers continually developing new boards for the Atari 800, everything from the original MYIDE boards to Incognito OS boards to RAM boards, some have IDE hard drive interfacing, others even have Western Digital 65816 CPU upgrades bringing the Atari 800's into the 16-bit world of computing at up to 7mhz of speed.


The Atari 400 and Atari 800 computers also have another very special expansion system called SIO (Serial I/O) which is a very early version of what would eventually become USB which is used today.  An interesting fact: The designer of the SIO port is Atari engineer Joe Decuir who is today, one of the patent holders of the USB interface, so it would seem his design would continue to evolve and in a sense ever PC and MAC user has a little bit of Atari in their systems today, thanks to Joe.


The SIO, just like today's USB allowed a great amount of power and flexibility to be added to the Atari 400 and Atari 800 computers.  Connecting devices (called Daisy chaining, essentially plugging one device into the next and next and so forth) onto this SIO chain allowed for the use of everything from Disk Drives, tape drives, Printers, I/O boxes with Serial and Pararell ports, Voice synthesisers, MIDI interfaces and other devices.   The downside to the SIO design was that is was an intelligent communications system, and each device required its own CPU to communicate and work on the SIO bus, so this made the devices inherently expensive.   The other downside to the SIO bus was its speed: 19.2K communication rate.   Though later hardware hackers were able to push the SIO to 38.4K speeds which greatly helped.


Another avenue of Expansion for the Atari 400 and Atari 800 computers were its front controller ports.  This were connected to the PIA chip (Parallel Interface Adapter) and many devices such as Modems, Real Time clocks and voice synthesisers used these ports.   Corvus Systems, makers of Hard drives and networking systems had an interface box that plugged into Controller Ports 3 & 4 on the Atari 800 and allowed the computer to use a hard disk system.   Corvus also sold boxes called MUX's that allowed multiple Atari 800's with Corvus interface boxes to plug into the same hard disk.  Up to 8 mux's could plug into a single 8 port mux allowing for a whopping total of 64 Atari 800's to be able to connect to and boot from a single Corvus disk system.


Once such commercial installation of a 64 Atari 800 computer mux network was set-up at Fordham Prepatory School in the Bronx, NY.   Run by Father Nick Lombardi, this network ran for many years.   A complimentary 3rd party OS board designed by David Small called The Integrator, replaced the Atari OS board and allowed the Atari 800's it was installed into to boot directly from a Corvus hard drive without the need of booting from Atari 810 or other floppy disk drive to load the Corvus driver to access the hard disk through the front controller ports.





Continue to Part 3...