Micro Instrumentation and Telemetry Systems (MITS) ALTAIR 8800

This system was donated by Neil Frieband. It was purchased as a kit, and assembled by a technician at Incoterm.

Serial Number 224019K. The "K" at the end of the serial number usually means that it was sold as a kit. From the date codes on the boards, it looks like this system is from early 1976.

The MITS Altair 8800 was designed in 1974 by Ed Roberts and Bill Yates at MITS in Albuquerque, New Mexico. It is based on the Intel 8080 CPU and the backplane is the S-100 bus. The Altair was featured on the cover of the January 1975 issue of Popular Electronics, and was sold by mail order. The designers were surprised when they sold thousands of the kits in the first month. Altair BASIC for this machine was the product that caused Microsoft to really grow.

This system has had the Grounding Modification performed that connects Logic Ground to Chassis Ground in many places. It has the one piece 18-slot backplane PCB, instead of the earlier multiple 4-slot backplanes.

We have binary images of 16K BASIC for this system. The plan is to program eight 2708 EPROMs with the BASIC images and then run BASIC from the EPROMs. We can then save and load BASIC programs to/from paper tape on the Teletype.

It would be nice to know where this serial number falls in the production range.

The "K" at the end of the serial number means that it was sold as a kit.

The boards from the foreground to the background are:

  • MITS 8080 CPU
  • MITS 4k Dynamic Ram
  • Cromemco Bytesaver
  • 88-2 Serial I/O
  • MITS 4k Dynamic Ram

Click on the image for a larger view.

Only one of the serial ports on the 88-2 Serial I/O board.

The large electrolytic capacitor was added to the +8V by the owner.

This system has a one piece backplane PCB, so it is not one of the original production run.

Neil Frieband shows off the MITS Altair 8800

The front panel without the metal overlay installed

The front of the MITS 8800 CPU board revision O

The back of the MITS 8800 CPU board revision O

The front of the first MITS 4K RAM board revision 02

All of the address jumpers are set to zero, so the RAM is at address 000000-007777 (Octal)

The back of the first MITS 4K RAM board revision 02

The front of the second MITS 4K RAM board revision 02

All of the address jumpers are set to zero, so the RAM is at address 156000-165777 (Octal)

This address range overlaps the first three EPROM sockets on the Cromemco board

We will likely move the address range of this board to 5k-8k so we can run the 8k BASIC

The back of the second MITS 4K RAM board revision 02

The front of the 88-2 Serial I/O board revision 0

The jumpers for port 1 are set for 110 baud 20mA Current Loop, and the address is set to 20-23 (0ctal)

The back of the 88-2 Serial I/O board revision 0

The front of the Cromemco 8K Bytesaver board

The jumpers next to IC9 set the board to the top 8K of the address space, so the base address is 160000

The Mostek MK4118 chip in socket 7 is a 1K x 8 static RAM with some wiring modifications to support the different pinout

This RAM chip should be at address 176000, and the EPROMs at 170000, 172000, and 174000

Socket 0 normally contains the Cromemco Bytemover software for programming the EPROMs, but it is empty

When the Programming Voltage is off, the Memory Protect signal is on

The back of the Cromemco 8K Bytesaver board