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Building a Clone MITS 8800

Orders placed to Mouser, Digi-Key and Jameco for components for the Interface Boards. A couple components on Mike's BOM on https://deramp.com are out of production or on backorder, but I was able to find equivalents - fortunately, these were passive components.

Still need to order power supplies.

I also need to do some research to confirm my understanding that the minimum system to bring it up consists of the Interface Board, CPU Board and a RAM board of some sort.

-Kevin
 
troj said:
Orders placed to Mouser, Digi-Key and Jameco for components for the Interface Boards. A couple components on Mike's BOM on https://deramp.com are out of production or on backorder, but I was able to find equivalents - fortunately, these were passive components.

Still need to order power supplies.

I also need to do some research to confirm my understanding that the minimum system to bring it up consists of the Interface Board, CPU Board and a RAM board of some sort.

-Kevin
Click to expand...

Hi,

Take a look at my Altair 8800c build page: https://www.brainless.org/Altair/Altair8800c/index.html This shows you the power supplies, the boards, the DIP switch and Jumper settings everything to get up 'n running in minimum effort and time.

The Check out the "The Lost Altair Software Library" page for other unpublished programs and information. https://www.brainless.org/Altair/ These pages are setup to make life easier for people just getting into the S-100 hobby.

After you have your computer working well, then you can get a modem and learn about vintage BBSes starting with the very first ... the 1976 CBBS. Much of the time I try to have mine up 'n running, but currently I am working out the problems with CBBS running on a J.A.I.R. SBC ... so hopefully soon that will be another "canned" setup for people to explore.


.
 
wperko said:
Take a look at my Altair 8800c build page: https://www.brainless.org/Altair/Altair8800c/index.html This shows you the power supplies, the boards, the DIP switch and Jumper settings everything to get up 'n running in minimum effort and time.

The Check out the "The Lost Altair Software Library" page for other unpublished programs and information. https://www.brainless.org/Altair/ These pages are setup to make life easier for people just getting into the S-100 hobby.

After you have your computer working well, then you can get a modem and learn about vintage BBSes starting with the very first ... the 1976 CBBS. Much of the time I try to have mine up 'n running, but currently I am working out the problems with CBBS running on a J.A.I.R. SBC ... so hopefully soon that will be another "canned" setup for people to explore.
Click to expand...

Thanks! I had found your page previously in my searches, but had failed to save the link. Bookmarked, now.

-Kevin
 
troj said:
Orders placed to Mouser, Digi-Key and Jameco for components for the Interface Boards. A couple components on Mike's BOM on https://deramp.com are out of production or on backorder, but I was able to find equivalents - fortunately, these were passive components.

Still need to order power supplies.

I also need to do some research to confirm my understanding that the minimum system to bring it up consists of the Interface Board, CPU Board and a RAM board of some sort.

-Kevin
Click to expand...
When you say "interface board" - are you referring to the Altair 8800c board that connects the front panel to the backplane? If you add just a RAM board to that, all you can do is key in a program from the front panel and watch the blinking front panel lights - not something that will keep you interested for very long.

The minimum "classic Altair system" was composed of the Altair 8080 CPU board, a RAM board (typically only 1K to start with), and the 2SIO serial board - with that you could key in a program from the front panel and run the program with an attached terminal. The next step up (if your terminal was not a Teletype machine with a paper tape reader) was to buy the Altair cassette interface board, which would allow you to load programs from cassette tape rather than having to manually key them in from the front panel.

My recommendation is that you buy both of the pre-built FDC+ and 88-2SIOJP boards described on the deramp.com site. Those two boards will provide you with serial interface ports, 64K of RAM, a monitor program in ROM, and a way to load software into the Altair using either a PC as a "serial port server" or a real floppy drive. That will get you up and running with the full vintage Altair experience, and with just three boards (the 8080 CPU board, FDC+, and 88-2SIOJP) you will be able to run most of the software that was ever developed for the Altair.
 
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troj said:
Thanks! I had found your page previously in my searches, but had failed to save the link. Bookmarked, now.

-Kevin
Click to expand...

Hi,

The page shows you which power supplies to get and how to connect them besides other very useful info.


.
 
hmb said:
When you say "interface board" - are you referring to the Altair 8800c board that connects the front panel to the backplane? If you add just a RAM board to that, all you can do is key in a program from the front panel and watch the blinking front panel lights - not something that will keep you interested for very long.

The minimum "classic Altair system" was composed of the Altair 8080 CPU board, a RAM board (typically only 1K to start with), and the 2SIO serial board - with that you could key in a program from the front panel and run the program with an attached terminal. The next step up (if your terminal was not a Teletype machine with a paper tape reader) was to buy the Altair cassette interface board, which would allow you to load programs from cassette tape rather than having to manually key them in from the front panel.

My recommendation is that you buy both of the pre-built FDC+ and 88-2SIOJP boards described on the deramp.com site. Those two boards will provide you with serial interface ports, 64K of RAM, a monitor program in ROM, and a way to load software into the Altair using either a PC as a "serial port server" or a real floppy drive. That will get you up and running with the full vintage Altair experience, and with just three boards (the 8080 CPU board, FDC+, and 88-2SIOJP) you will be able to run most of the software that was ever developed for the Altair.
Click to expand...

Yep, that's exactly what I mean by "interface board".

Your suggestion on the two boards from Mike make complete sense.

-Kevin
 
I was showing some of this to a friend a bit ago.....and realized I probably have close to 2,000 solder joints to make.

I've got the 9 slot backplane and I've got the connectors, so I plan to fully populate it - easier to do it now than have to later pull it out and add more.

-Kevin
 
troj said:
I was showing some of this to a friend a bit ago.....and realized I probably have close to 2,000 solder joints to make.

I've got the 9 slot backplane and I've got the connectors, so I plan to fully populate it - easier to do it now than have to later pull it out and add more.

-Kevin
Click to expand...
Soldering S100 connectors to the backplane is a tedious and monotonous project. Spread out the task over a few days. A bad solder joint in this location due to lack of attention will be very difficult to diagnose. Your plan to fully populate the board is great - although expensive to do in one shot, tearing down an S100 system to install more connectors is no fun.
 
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Chuck(G) said:
The original shipped with the SIO0 board--a single UART (either GI or Rockwell TR1602 type) with bitrates set by jumper.
Click to expand...
The original Altair did not ship with any serial interface board unless purchased as an extra-cost option but yes, when they started offering packaged "systems" the SIO board (one of three versions depending on interface) was included.
 
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hmb said:
Soldering S100 connectors to the backplane is a tedious and monotonous project. Spread out the task over a few days. A bad solder joint in this location due to lack of attention will be very difficult to diagnose. Your plan to fully populate the board is great - although expensive to do in one shot, tearing down an S100 system to install more connectors is no fun.
Click to expand...

My original plan was to only populate 4 of the slots, and I bought connectors accordingly. Then I stumbled across Newark having them on sale for $4.15 each, so I bought the 7 they had in stock.

Agreed on the tedium. I'll definitely be taking my time on them and going over joints with a magnifying glass, to make sure they're all good.

-Kevin
 
hmb said:
The original Altair did not ship with any serial interface board unless purchased as an extra-cost option but yes, when they started offering packaged "systems" the SIO board (one of three versions depending on interface) was included.
Click to expand...
It shipped along with 2 4K DRAM boards in the original "kit for $1,000". I bought one.
 
Chuck(G) said:
It shipped along with 2 4K DRAM boards in the original "kit for $1,000". I bought one.
Click to expand...
What you purchased was one of the early MITS packaged "systems" that included several additional boards.

The "big deal" with the Altair was that you could buy one for under $500 and indeed you could - but at that price you just got the box with front panel, backplane, and CPU board. At minimum one would also need to buy one of the 512 or 1K RAM boards, which would allow one to at least play with the front panel. Realistically to do anything useful more RAM and a serial board was necessary - hence the more expensive "systems" they listed on their price list.
 
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I dont understand all the heavy shilling for the 9 slot repro backplate since it totally lacks provisions for the mechanical support brackets. The 4 slot repros are vastly superior in this regard IMO. Plus if you're doing a repro build with modern cards usually you can get away with only needing 4
 
Chuck(G) said:
When did the SIO 2 boards come out? I don't think they originated with the initial 8800 selection.
Click to expand...
The schematic for the 2SIO is dated 12-3-75 so the board probably shipped in early 1976, a bit over a year after the initial release of the Altair 8800.
 
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hmb said:
What you purchased was one of the early MITS packaged "systems" that included several additional boards.

The "big deal" with the Altair was that you could buy one for under $500 and indeed you could - but at that price you just got the box with front panel, backplane, and CPU board. At minimum one would also need to buy one of the 512 or 1K RAM boards, which would allow one to at least play with the front panel. Realistically to do anything useful more RAM and a serial board was necessary - hence the more expensive "systems" they listed on their price list.
Click to expand...

Hi,

I built an early 1975 Altair 8800 computer kit ... I ordered it with a 6-Slot backplane, CPU board and 1K RAM board, besides the cabinet and power supply, but it still had the 4-Slot backplane in the kit.


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It's been a bit, but I've finally had some time to start assembly.

9-slot backplane is started. I just need to drop in the S100 connectors, and the fuses.

The front panel has been assembled and installed into the case.

Before I go much further on anything with the case, I need to determine how I'm going to mount power supplies - looks like I'm going to need to drill some mounting holes for that.


IMG_2272.jpgIMG_2280.jpgIMG_2288.jpg
 
As far as we're getting today, because someone (me) forgot to check the size of sockets needed. Order placed for the necessary sockets; until they arrive, this board goes no further. I also have mounting screws on order for the power supplies.

I could start on the CPU board, but I don't have to have multiple boards in progress at the same time, and risk mixing up parts.

I've also got an email out to Martin Eberhard inquiring about an 88-2SIOJP.

-Kevin


IMG_2290.jpg
 
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