This page last updated Mar 12 2021 (c) Herb Johnson 2021.
![[Altair 8800]](altair2.jpg)
First offered to the public in January 1975 by MITS in a Popular Electronics front-page article, this is an image of an Altair 8800 computer. It was designed by MITS founder and president Ed Roberts in 1974. It initially contained several major components: a 4-slot motherboard with bus connectors of 100 pins each, soon to be called the "S-100 bus"; a CPU card with an Intel 8-bit processor (8080); a memory card initally with 256 BYTES of memory; a front panel of lights and switches; and a power supply. The design of the computer was completely "open"; in fact it was sold as a kit, with full documentation including schematics and operating descriptions. Other cards were to follow, and they did.
![[Altair inside]](alt1x.jpg)
Here on the left is an inside view of the Altair, with various cards. The card with the white connector and white wires is the CPU board; behind it are two memory cards; the back is an I/O card. The earliest Altair had just a four-slot motherboard, additional slots were added four at a time. Note that in the read of this Altair is a row of capacitors, part of the earliest Altair power supplies. Every surviving Altair today will likely have different cards, some of NONE of which may be MITS cards.
![[Altair memory]](memx.jpg)
To get some idea of this level of technology, compare this MITS *one thousand byte* memory card to the *one Megabyte* SIMM memory, both pictured here on the left. The earliest MITS memory card was sold with only TWO memory chips, 2101 Intel memory with 256 X 4 bits per chip. This board had six more 2101's added to bring it up to a "full" 1K bytes of memory. Note that the circuit traces and the edge connector on this board are grey; that's "tinned" in the circuit-board trade and this is very distinctive of early MITS Altair cards.
MITS and Pertec
Other sites have more history about Ed Roberts, MITS and the Altair product line; so my notes on MITS as a company are brief. MITS made a number of electronic instruments before offering the Altair. MITS, and another computer product company called ICOM, were bought by disk drive manufacturer Pertec, Inc. in mid-1977. MITS products became part of Pertec's "PCC MicroSystems Division". Some MITS items may be branded "Pertec" or "ICOM". Percom accumulated a number of computer product companies over time.
According to one former Pertec employee Tom Sanderson, Pertec designed some additional computer products and systems which were only software-compatible with the Altair; as well as other computer products. Others say MITS-based product production ceased in mid-1978. All those products were later dropped by Pertec.
Death of Ed Roberts, MITS Altair CEO and Altair developer
On April 1 2010, Dr. Ed Roberts, M.D., died of pneumonia, at age 68. He was the founder of MITS in 1969, and the designer of MITS' Altair 8800 computer in 1975 which included the "Altair bus", the 100 pin connectored backplane which became known as the "S-100" bus within a few years. We have a tribute page to him at this link. Meanwhile, my S-100 home page lists over 140 companies which produced S-100 cards or systems; and has links to many pages about S-100 technology and to individual S-100 company products and histories. Their legacy, and the legacy of all the companies and software and hardware subsequently created by those employed by those companies, are also a tribute to Ed Roberts. - Herb Johnson
common questions
Why the "S-100 bus"? And why the name "Altair"? These questions are asked so often I devoted a Web page to their origins.
Was the MITS Altair 8800 the first personal computer? Nope, but it was important and read Web this page to see why I believe that. I point there to a 2007 Web site which had a good description of other "first" and "personal" computers.
I'll say more below about the importance of the MITS Altair.
What is the status of MITS and Pertec today? Pertec was bought but maintained as a subsidiary by a number of companies. First in 1979, by German company Trimuph-Adler; in April 1986 Volkswagen, who at various points funded Pertec, kept PCC after selling Trimuph-Adler to Olivetti. Other references suggest that Pertec Computer Corporation persisted as a corporation through at least 1982. In 1986, the LA Times reported that PCC was acquired by Digital Development Corp of San Diego in Nov 1986. There is a 1989 and a 1990 reference to a "DDC Pertec" in Chatsworth CA, as a manufacturer of tape and disk drives. In 2006 EPA reports a commercial facility exists at the same Chatsworth address. A French company called "Pertec" seems unrelated.
Why is the MITS Altair 8800 important?
While the Altair was not the very first microprocessor-based "personal" computer or computer kit, the MITS Altair 8800 is often cited as the "first" POPULAR personal computer due to its availability and widespread press coverage; its low cost which allowed thousands to buy it; and its expandability which led to the founding of many companies to offer S-100 bus compatible products. The first compatible company was IMSAI Inc. with their IMSAI 8080. IMSAI named their Altair-compatible bus "the S-100 bus" due to the 100-pin connector. Here is a list of the Altair bus lines.
This bus was adopted by
over 100 companies large and small over the next several years; the bus became an IEEE standard. An early MITS software product, MITS BASIC, was written by a two-person company called "Micro-soft"; the persons were Bill Gates and Paul Allen. Competitor IMSAI was a very early adopter of Digital Research's CP/M which was the dominant microcomputer operating system of the era.
This history makes a strong case that MITS and the Altair 8800 catalyzed the microcomputer computer revolution of the mid-1970's. However, others reasonably debate that other products and events were also important or critical to the history of personal computing or information technology. History, after all, is a backward-looking opinion about events. In history, it is very rare that one person, one idea, or one product exclusively determined the future, or was created in a vacuum. This site is primarily devoted to S-100 history; there is no debate as to the first S-100 computer.
Altair 8800 faux copies, replicas and originals
When I first developed this Web page in the early 2000's, only a few people were producing replicas
of MITS Altair 8800 boards. The cost to produce 5 by 10 inch PC boards was high, board layout software
was expensive and not many people had those skills or interests in duplicating old work. (Some designed
new S-100 cards.) A few people produced what I call "replicas" - actual copies of individual MITS Altair 8800 boards, or even chassis, copied to the smallest detail. But at the time a replica cost as much as an available
old original MITS computer! To avoid the obvious problem of confusing replicas with originals (obvious to me, not the first producers), eventually details of differences were published. So, since MITS boards themselves varied over time - before you buy a "MITS" item, confirm its origins!
In the 2007's and later, a few other people produced what I call "faux Altairs". Those were boxes with
front panels which looked like an Altair but inside was some kind of microcontroller - what
we in 2020 would call an Arduino board, or Microchip PIC on a small PC board. And that non-Altair, non-8080
controller, operated the lights and switches and emulated the 8080 and serial IO. Of course
these are not intended to be outright copies. They offer a relatively inexpensive means of obtaining the Altair experience. Again - know what you are buying.
And of course, even in the 1990s there were software emulators of the 8080 and of the entire MITS Altair. Even the IBM PC original of 1981 could run an 8080 simulator program. But it took a few more
years before a "PC" could emulate an Altair faster than the Altair actually ran! Emulators are very useful in
restoring and verifying vintage software, even regenerating source codes.
As I update this document in 2020's, there's any number of ways you can replicate some facet of the
MITS 8800 Altair "experience". The costs are cheaper, the means simpler to acquire. You can buy a complete board to run Altair 8800 software, even store files. You can buy board copies - not
identical but functionally the same - of MITS Altair
boards. Or, "send the Gerber files" of them, to some printed-circuit board shop to have them produced.
You can run free board design software and make your own. And,
there's bunches of Arduino and Rasp Pi class microcontrollers to run faux Altair front panels. Also, there's a number of multiple-computer software emulators, which
run MITS software. They have realistic-looking operating screen images of the MITS front-panel.
And of course, there's many vintage (or modern designed) S-100 boards and systems one can acquire, restore and operate. - Herb Johnson
MITS and Altair resources
I have a seperate Web page of S-100 related Web pointers. There are many Web sites dedicated to the Altair 8800, or to MITS; and sites which include the 8800 among many other old computers.
In Feb 2021, I had a conversation with a former MITS/Pertec system service tech. They informed me about
some interesting problems with the MITS Pertec S-100 backplane and connectors. Apparently the
connectors became intermittant due to stresses produced by screwing the "ears" of the connector into the
chassis and backplane board. With permission I gathered that converstation and here's the notes
from that MITS Pertec service tech. - Herb
In 2011 I had some email exchanges with Martin Eberhard about his restoration of a 6800-based MITS 680. It's an interesting little system. Not S-100 but it used the same bus connectors!
In the fall of 2011, I corresponded with Martin Eberhard, another 6800 system owner. He has a number of MITS "Altair 680" systems. MITS
is less-well known for their Altair 680, an non-S-100 based 6800 computer. I created a Web page from Martin's correspondence about his work on restoring his Altair 680 system and some software he wrote to support it. [I do not have a MITS 680 system.]
Former Pertec employee Tom Sanderson has a nice MITS and Altair Web site called "Virtual Altair" about the various product lines associated with MITS, Pertec and Icom. He's actively working on restoring hardware of the period.
For a list of available Altair docs look below.
Here is a list of the IMSAI and Altair bus lines.
For a list of all S-100 docs click there.
Again, here is how to order S-100 stuff and email @ me.
SOme of the earliest floppy disk controllers were adapted to the MITS Altair 8800. read this Web page about the first floppy controllers for CP/M.
Note: since the early 2000's when I first offered this documentation, and particularly
in the 2010's, a number of MITS Altair archives are available on the Web. That's thanks to
the people restoring and operating MITS Pertec boards and systems. Web search will find
thos archives. But: I may have some docs they do not! - Herb Johnson
Altair (MITS) and related documentation available (copies) are describe below.
PAY CLOSE ATTENTION to the descriptions below when ordering. Please
include these descriptions when ordering. We will accept orders
for complete manuals or for the SPECIFIC sections named with
page counts. Price is based on page count so BE SPECIFIC WHEN
ORDERING, USE THESE EXACT DESCRIPTIONS.
Original 1975 Altair 8800 documents:
Altair 8800: front panel address and data switches on solid grey
background
Altair 8800a: as above, some changes in f.p. and logos
1) Altair 8800 Assembly manual, 103 pgs
For assembly of front panel, CPU, chassis, power supply, bus.
assembly hints, sketches of cards & chassis, sketches of parts
and their insertion, wiring directions, parts lists. No schematics.
2) Altair 8800 Operators manual, 100 pgs
Tutorial. Describes binary arithmetic, organization of 8800 system,
programming of 8080 processor, front panel operation and display,
descriptive list of 8080 instructions. No electronics references.
3) Altair 8800 "Theory of Operation, Manual & Schematics" 24 pgs
Covers CPU, 1K RAM, power, display/control panel.
Descriptions of circuit operation. Bus definition.
Schematics. Checkout procedure.
Altair 8800b documents: 1976, reprinted June 1977
8800b: front panel address and data switches on dark background
with white horizontal strips
1) Altair 8800b Documentation, 280 pgs TOTAL except Ch 5.
front panel with address and data switches version,
bus, power, interface board, & CPU schematics
operation of front panel. Troubleshooting. Parts list.
Intel 8080 Users Manual and Intel chip data sheets.
This manual is divided as follows:
Ch. 1 - introduction and content lists. 12 pgs
Ch. 2 - Operators Guide 15 pgs
"Intel 8080 Microcomputer System User's manual" - 60 pgs
Ch. 3 - Theory of Operation 28 pgs
Intel chip data sheets: 30 pgs
Schematics & bus definition: 30 pgs
Ch. 4 Troubleshooting: 68 pgs
Does not include chapter 5 on assembly of system or cards.
Appendix A - parts lists: 9 pgs
2) Altair 8800b chapter 5: Assembly - 75 pgs.
Assembly instructions for 8800b system.
Was not distributed by MITS with assembled 8800b systems.
Altair 8800b-t: July 1977
TURNKEY system, run/stop and reset switches ONLY, BLACK background.
1) Altair 8800b-t Turnkey Computer Documentation, 83 pgs TOTAL
Front panel with run/stop/halt switches version, Turnkey module.
Schematics and description for turnkey control card and front panel.
Does not include chapters "Intel 8080 users manual" below.
Does not include chapter 5 on assembly of Turnkey system or cards.
Includes the following chapters:
Ch 1: Introduction and contents lists: 6 pgs
Ch 2: Theory of Operation, Schematics: 24 pgs
Ch 3: Advanced Operation: 20 pgs
serial port and power operations
Ch 4: Troubleshooting and index: 8 pgs
Does not include Chapter 5 on assembly of system or cards.
Appendixes: 20 pgs
parts lists, 230V operation, bus description
2) Altair 8800b-t Turnkey chapter 5: Assembly., 110 pages.
(Confirm we have this available.) How to assemble the 8800b-t.
Was not distributed by MITS with some assembled 8800b-t systems.
3) Intel 8080 microcomputer system users manual, 84 pages
As distributed with "8800b Turnkey Computer" docs.
Duplicates information in chapter2 of 8800b manual above.
Copy of Intel's 8080 hardware and instruction set description,
hardware chip descriptions for 8080, 8212, 8216, 8224.
4) "MITS 300 Computer System -
Theory of Operation and Maintenance Manual - Turnkey Module"
doc #200786A June 1978
Chapter 4 ONLY on Theory of Operation, pgs 4-9 to
4-28, 20 pgs, no schematic, for Turnkey board for 8800b-T
system, plus schematic and description for run/stop front panel.
5) Turnkey Module modifications, various notes from MITS:
The 88-SYS-CLG modification brings the 8800b/8800bt to a full 64K
by making the the PROMS "phantom" on the Turnkey Module
* Tech Notes on 88-SYS for 8800B-T Oct 79, 8 pgs
* Tech notes as above, different version, 7 pgs
affects boards 200360, 200375, 200359
Altair 8800b-sm, 8800b-dm: TURNKEY system, run/stop & reset switches, floppy drive
1) Altair 8800b-sm & -dm Computer Documentation, 100 pgs
Front panel with run/stop/halt switches version, Turnkey module.
Schematics and description for turnkey control card and front panel.
Does not include chapters "Intel 8080 users manual" below.
2) Intel 8080 microcomputer system users manual, 84 pages
As distributed with "8800b Turnkey Computer" docs.
Duplicates information in chapter 2, 8800b above.
Copy of Intel's 8080 hardware and instruction set description,
hardware chip descriptions for 8080, 8212, 8216, 8224.
Altair disk systems and controllers manuals:
Note: be advised that anyone purchasing the 88-DCDD manual or the 3202 manual
may need the NWD mod doc and may wish to have all available
versions of the controller schematics. A former Pertec employee said
"I think it is likely that most old controllers were modified for "NWD" timing".
MITS Timsharing BASIC Version 2 Reference Manual (copy)
Feb 1979, 60 pages
diskette based multiuser BASIC, using 3202 controller/drive system
Altair Disk Operating System Documentation (copy)
June 1977, 127 pages
Chapters on monitor, text editor, assembler, linker, debug
NOT CP/M!
MITS Memory Diagnostics, doc #103239, 4 pgs
Says pgm is "&MTST" on a MITS "DOS disk"
I have a disk copy, but the diskette is 32-hard-sectored.
I'm told the disk can be read in the MITS 88-DCDD single-drive cabinet
or the Pertec 3202. The "(NWDD)" on the label indicates the New Write Delay was
used to write the diskette. The "Pertec Application Note - Hard Sectored"
provides background on Pertec's view of hard-sectored formatting.
Altair 88-DCDD Floppy Disk Documentation (copy)
July 1977, 318 pages total
Pertec FD-400 drive, two board floppy controller, disk buffer board
"board 1" rev 0-X2 and rev 0-X4
"board 2" rev 0-X2 and rev 1
assembly, tests, schematics, parts lists
hand notes for 8-inch drive timing of one-shots (74121's)
includes "Pertec FD400 Disk Drive Installation Notes", Mar 1977, 18 pgs
"Pertec Application Notes - Hard Sectored
Formatting for FD400 Flexible disk drives". 1976, 17 pages
Pertec / PCC "FD400 FD500 Flexible Disk Drives"
manual 600500, 1978. 90 pages
for drives 600281 (FD4X0, FD5X0) , 600261 (FD51X)
Schematics offered seperately as below
"Pertec FD Control B" schematics, document 600260
for board 600261. 7 sheets 11X17, 1977
"Pertec FD Control D" schematics, document 600280
for board 600281. 6 sheets 11X17, 1977
"Pertec FD BASIC II DC" schematics, document 600320
for board 600321. 7 sheets 11X17, 1975-76
"Pertec FD BASIC II A" schematics, document 600265
for board 600266. 8 sheets 11X17, 1976
"Pertec FD BASIC II AC" schematics, document 600250
for board 600251. 6 sheets 11X17
Altair 88-MDS Minidisk Documentation Preliminary
July 1977 w/ updates April 1978, 100 pages plus notes
88-MDS two-board system and 88-MDDR 5.25 inch drive
schematics, PROM listings, some code, more
6 pgs of hand-written "tech notes" poorly reproduced
hardware is apparently similar but not identical to 88-DCDD
Various notes, FD400 and 88-DCDD cards, for NWD - New Write Delay - modification
* "Disk Hardware Notes" by Tom Dursten, 88-disk control mods, FD400, 2 pgs
* Altair Disk test programs, Apr 1976, 5 pgs w/ assembly source
* "Disk Hardware Notes" by Tom Dursten, timing on FD400 controller one shots, 2 pgs
* Disk Control board DB-37 to 20+20+10 pin connectors, cable construction, 7 pgs
"Altair Hard Disk 88-HDSK Preliminary Documentation", Oct 1977
138 pgs plus 4 sheets 11X17 schematics
*new* 35 page addendum, with 8X300 code (PDF available)
MITS interface to Pertec D3422 drive, 5MB fixed 5MB removable
Docs cover processor card with 8X300 processor which cables to the
MITS (S-100) 88-4PIO parallel card; and data card; and interface card to
Pertec drive. The three cards are boxed separately from the
Pertec drive and the Altair system.
"MITS 3200 Users Manual - Disk Controller Boards"
doc 250284A, April 1978. 82 pgs manual, 18 pgs 11X17 schematics and cabling
Theory of Operation for boards #1 and #2,
"MITS 3200" Disk Board #1 and #2 schematics, appendices. document 250284A
also available; 6 pgs 11X17 for Disk Board #1 and #2 schematics
from a March 1976 88-DCDD "preliminary" manual. They are an
earlier version, does not have R/C delay circuits or trimpots
as added to 3200/250284A above see "3200/250284A notes" for discussion
Other Altair hardware documents:
Altair 8800 88 2-SIO docs, 50 pgs
Theory of operation, schematics, assembly, parts list, serial
connectors and signals.
Altair 88-PMC PROM memory card, 30 pgs
1702 PROMs. Theory of operation, schematics, assembly.
Altair 88-4MCD "4K RAM Board", 26 pgs
Sept 1975. TMS 4030 or C 2107A 4K by 1 RAM chips, along top of card.
Circuit description, schematic, assembly and test instr., errata.
Altair 88-S4K Synch 4K RAM docs, 60 pgs
Feb 1977. TMS 4060 4K by 1 RAM chips, along right of card.
Logic descriptions, schematics, assembly, test, signal waveforms.
Altair 88-16K static RAM card, (88-16 MCS) 26 pgs
1977. THeory of operation, timing, layouts, schematics, assembly.
Altair 88-VI/RTC vector interrupt, real-time clock, 36 pgs
1976. THeory of operation, schematics, assembly, errata
Altair 88-16MCD dynamic memory card, 55pgs
July 1977. MK4096 4K by 1 chips.
THeory of operation, schematics, assembly, troubleshooting.
Altair 88-4 Parallel I/O card (4PIO), 28 pgs
1975. Four port parallel card: operation, assembly, schematics.
Altair 88-ACR audio cassette interface, 53 pgs. (2 cards)
June 1975. SIO-B serial card & ACR modem board.
MITS 3200 series Floppy Disk System *preliminary*, 18 pgs
MITS 3202 schematics and cabling sketches only
Altair 88-NO power controller, 31 pages
8 relay AC control card: theory, schematics, assembly, test.
Altair 4K Dynamic RAM Assembly manual, 24 pgs
Percom CI812 Cassette/Terminal I/O, schematics only, 10 pgs
Altair software and miscelaneous
Altair BASIC reference manual, w/Extended BASIC, Dec 1975, 104 pgs
Mits Programming System I, rev 2.2, 27 pgs (line printer)
Altair Programming System II rev 3.0, 58 pgs
assembler, debugger
Altair Software Library update, 60 pgs
short descriptions of several dozen programs, coding sheet,
source listings of: JAMON, kill the bit, target.
JAMON is five pages of code listings. Commands are to load
and dump and "go", all in octal (bleah). Kill the bit is a
one-page listing of a game using the front panel only.
Target is a 9-page listing using a VDM video display and
"bit 7 of an input device" (front panel?).
Altair 4/1/76, 7/1/76, 8/1/77 retail price lists, 20 pgs
MIcrosoft BASIC Reference Manual, Jan 1977, 128 pgs
for BASIC CP/M version 4.41 as MBASIC.COM
includes an April 1977 addenda, appendix B on CP/M BASIC
similar to Microsoft BASIC reference manual for MITS, Jan and July 1977
"MITS Altair Production Test Procedures - Altair 8800B Systems
Altair 680b Systems". 24 pages. Production test procedures for
8800a, 8800b, & 680B chassis, and individual MITS board products.
16K MCS may be latest product covered; no date on document.
MITS newsletter/magazine "Computer Notes":
(note: 11 X 15 editions will be copied to reduced size 8 X 11:
if you want 11 X 17 copies I must charge for TWICE as many pages.)
Vol 1 Issue 10, March 1976, 11" X 15" - 12 pgs
Vol 1 Issue 12, May 1976, 11" X 15" - 16 pgs
Vol 2 Issue 1, June 1976, 11" X 15" - 20 pgs
Vol 2 Issue 2, July 1976, 11" X 15" - 24 pgs
Vol 2 Issue 3, Aug 1976, 11" X 15" - 24 pgs
Vol 2 Issue 4, Sept 1976, 11" X 15" - 16 pgs
Vol 2 Issue 5, Oct 1976, 11" X 15" - 12 pgs
Vol 2 Issue 6, Nov 1976, 11" X 15" - 32 pgs
Vol 2 Issue 7, Dec 1976, 11" X 15" - 16 pgs
Vol 2 Issue 8, Jan-Feb 1977, 8" X 11" - 28 pgs
Vol 2 Issue 9, March 1977, 8 X 11, 24 pages (from copy)
Vol 2 Issue 10, Apr 1977, 8" X 11" - 28 pgs
Vol 2 Issue 11, May 1977, 8" X 11" - 28 pgs
Vol 3 Issue 1, June 1977, 8" X 11" - 28 pgs
Vol 3 Issue 2, July 1977, 8" X 11" - 20 pgs
Vol 3 Issue 3, Aug 1977, 8" X 11" - 20 pgs
Vol 3 Issue 4, Sep 1977, 8" X 11" - 28 pgs
Vol 3 Issue 5, Oct 1977, 8" X 11" - 36 pgs
Vol 3 Issue 6, Nov 1977, 8" X 11" - 36 pgs
Vol 3 Issue 7, Jan-Feb 1978, 8" X 11" - 36 pgs
Herb Johnson
New Jersey, USA
follow this link to email me or to order.
Copyright © 2020 Herb Johnson