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Building a Clone MITS 8800

T

troj

Experienced Member
Joined
Apr 22, 2018
Messages
115
Location
Bellevue, NE
I'm starting to think about diving down the rabbit hole of building an 8800 clone. It goes back to the first computer I was exposed to back in the 70s, which I'm fairly sure was an 8800. I learned to program in 1979 on the TRS-80 Model 1, and I have several of those....but I've never gone back to the 8800.

Thing is, if I do this, I don't want a Pi-based emulator. I want actual hardware. Buying an actual 8800 for $5K+ isn't realistic at this time, but in poking about, it appears that I can accumulate the parts to build a clone that looks and operates like the real thing.

For boards, it looks like Gary (Kaufman?) at the-planet.org sells both front panel and CPU boards. I've found CPU board parts kits on eBay.

The part that seems to be the biggest challenge is the chassis - I had thought I found a source for that, but now I can't find one.

-Kevin
 
It's a pity Grant Stockly's kit project never got going in earnest. He had an amazing kit developed. I've heard rumblings from others that they may try to do something to his level of detail in near future.

BTW not all 8800s sell for $5k. That price is usually the very original, low serial Rev 0 machines. If you can put up with stuff like not having the front badge or things like PSU or backplane aftermarket replacements, you can get a deal. I got a complete working 1K Altair 8800 for $2000 last Christmas.
 
I wanted to do the same but fell in love with the AitairClone because I found assembling an S100 was too expensive and unreliable.
Unfortunately it seems they are no longer sold. :(
 
NeXT said:
I wanted to do the same but fell in love with the AitairClone because I found assembling an S100 was too expensive and unreliable.
Unfortunately it seems they are no longer sold. :(
Click to expand...

If you want a similar look, but less expensive, [Adwater & Stir has the AltairDuino available](https://adwaterandstir.com/product/altair-8800-emulator-kit/). I've got a Pi-based PDP-8 emulator that's along the same lines and is very cool.

I actually considered this route, but decided to go down the 8800c path, instead. It'll take me longer to accumulate the parts, but it's what feels "right", to me.

-Kevin
 
My recommendations:
- buy the Altair CPU board repro from Gary Kaufman, who sells them via eBay.
- buy the 8800c enclosure and front panel board set from the deramp.com web site. His revised but otherwise authentic-looking front panel board set is far more reliable than the original Altair FP, which has its share of issues including the problematic bundle of wires required to connect it to the backplane. JMPrecision in the UK used to sell an accurate reproduction but they no longer have stock (it appears they are getting out of the business), and I'm not sure Gary Kaufman still makes them available either.
- buy the 88-2SIOJP made by Martin Eberhard - link to purchasing information is also on the deramp.com web site. It is a functional reproduction of the Altair 2SIOJP, for which there is currently no true reproduction available.
- I also highly recommend you consider getting the Altair FDC+ available on deramp.com. It provides an easy way for you to use a real mechanical floppy drive with your system, and that board will also provide your system with the 64K of RAM required.

The only other thing you will need is an S100 backplane - build the one linked to on the deramp.com site, rather than a reproduction of the original Altair backplane.

There have been a few references above to Grant Stockley's "Altair Clone" described at altairclone.com. As mentioned that product has not been available after the first run was sold a decade ago, and I think it is unlikely that project will be brought back to life.
 
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I would also have a look at the Adwater and Stir kits

i have done some amazing stuff.

i looked at the hardware clones myself.

i also looked at the highnibble kits.

the Adwater setup is really amazing you can add to the hardware extend it with additional serial ports and the I/O Back plane.

the cost is minimal, you can add all manor of real hardware to it and have good reliability.
 
furball1985 said:
I would also have a look at the Adwater and Stir kits

i have done some amazing stuff.

i looked at the hardware clones myself.

i also looked at the highnibble kits.

the Adwater setup is really amazing you can add to the hardware extend it with additional serial ports and the I/O Back plane.

the cost is minimal, you can add all manor of real hardware to it and have good reliability.
Click to expand...
...except the original poster mentioned right at the start they were not interested in Pi-based emulators, which I expect includes the Altair-Duino sold on the "Adwater & Stir" web site.
 
hmb said:
...except the original poster mentioned right at the start they were not interested in Pi-based emulators, which I expect includes the Altair-Duino sold on the "Adwater & Stir" web site.
Click to expand...

Correct.

The Adwater & Stir emulator is a really nice setup....but not what I'm looking for.

-Kevin
 
troj said:
Correct.

The Adwater & Stir emulator is a really nice setup....but not what I'm looking for.

-Kevin
Click to expand...

Hi,

I higly recommend going the Altair 8800c route for starters. It's quick, affordable, resalable and once you're comfortable with the machine, you might want to start adding other S-100 boards and/or terminal emulators to the computer.

As you accumulate S-100 boards, you can then move into resurrecting an old original Altair 8800 or IMSAI 8080 etc.



.
 
So, already on order....

2 x CPU board parts (eBay)
2 x CPU boards (Gary)
1 x 4 slot backplane (Gary)

Mike is going to get back to me with a total for the case and front panel board set.

Will need to acquire the components for the front panel board set. Research to be done to find either a ready to buy set, or a BOM. Mike has the BOM in his detailed instructions.

-Kevin
 
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troj said:
So, already on order....

2 x CPU board parts (eBay)
2 x CPU boards (Gary)
1 x 4 slot backplane (Gary)

Mike is going to get back to me with a total for the case and front panel board set.

Will need to acquire the components for the front panel board set. Research to be done to find either a ready to buy set, or a BOM. Mike has the BOM in his detailed instructions.

-Kevin
Click to expand...

Hi,

I suggest getting the 9-Slot backplane/motherboard from Todd Goodman ... search "9 slot" on the page ... $15 ... The larger board allows to space the S-100 boards further apart for added cooling.
https://www.retrobrewcomputers.org/doku.php?id=boardinventory

Because of the cost of edge connectors ... I also suggest an arrangement of leaving some edge connectors OFF every other slot to save money, unless money isn't that important. As you can see in the image below I have more empty slots than used slots ... although I do plan to add two more boards into the computer besides the front panel connector board, the reproduction MITS 8080 CPU board, the Eberhard 88-2SIOJP board and the FarmTek FDC+ board. I want to add a 3P+2S board and a reproduction SciTronics RTC board. That all makes a very full-function Altair 8800 computer.

I've designed two types of card guides depending upon which edge connectors people have ... bottom flange or mid-flange:
https://pinshape.com/items/110209-3d-printed-9-slot-card-guide-for-bottom-mid-flange-edge-connectors

One day when I open this system up again, I'll add my card guides ...


.
 

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I really like the idea of exact clone S-100 boards and S-100 computers. Because you can mix in original boards when you can find them or use clone boards.

One advantage I think of exact clones of the boards is that all the manufacturer data, software/firmware routines, schematics applies to the board. Most of the data for most of the S-100 boards are available from S-100 computers. There is some absent data, but most of it is there.

Very good S-100 boards in my view are ones like a N* double density board that are basically plug & play and you can get an S-100 computer running CP/M in no time with a pair of 5.25" disk drives and Mike's VSG board if you want to use soft sectored media. I think the N* double density board should be targeted for cloning. Also another great board is a video card like the VDM-1 which basically will give the computer the same video system as the SOL-20.

I replicated the Dazzler pcb's for use in my SOL-20 and made the replicas spot on, including all the small components, so it perfectly matched the original and is indistinguishable from it, except the boards are better quality with gold plating throughout. As a result I had no trouble with it, and it worked first pop.

I would like to see many more vintage S-100 exact clone boards made, because some of the original boards are getting rare and expensive now. And I applaud the makers of other S-100 exact clone boards.

Unless they are exact clones, I cannot really see what the interest could be, because it is the vintage designs that we want to re-capture the magic of that era, and emulation on modern hardware does nothing for me personally. And if we are going to build replica vintage computers, we need very close to exact copies.

Recently, I did another cloning project , outside the field of vintage computers, it is a near exact replica of the Manipulator & 20.005 MHz transmitter module used in the Sputnik-1 Satellite. Some may be interested in the lengths I went to, to get it close, including importing many parts from Ukraine. Nobody in the past had described how the Manipulator worked until now, or replicated it (it is quite astonishing), and other replicas made of the transmitter were hopeless on veroboard. I had to learn how to cut glass and ceramic to complete the replication:

 
wperko said:
I suggest getting the 9-Slot backplane/motherboard from Todd Goodman ... search "9 slot" on the page ... $15 ... The larger board allows to space the S-100 boards further apart for added cooling.
https://www.retrobrewcomputers.org/doku.php?id=boardinventory
Click to expand...

Yeah, that makes sense. I think I'm going to start with the 4 slot, with the ability to upgrade to the 9 slot - options are a good thing.

First order of business will be a basic running computer. Fortunately, no SMD components, so my bad eyes and shaky left hand can handle the soldering.

-Kevin
 
I have stock of Altair and IMSAI cpu cards, see http://www.the-planet.org
They are (imho) a nice reproduction of the original cards, with hard gold contacts.
I sell them on Ebay, Tindie (and directly for $5 less as I don't have fees that way and pass along the savings).

Although the Altair is historically important, the clock circuitry on the Altair can be pesky to get working. The IMSAI cpu card is a better design in my experience.

I like to make sure that folks really want the reproduction of the original Altair Backplane before they order.
I stock a 4 pin backplane that is authentic (the original Altair), but it really is just interesting if you want an historically correct computer.
Edge connectors are not necessary, but there is a .stl file for them on my website.

I agree that probably the best "starter" backplane is the 9 slot one developed by the S100Computers.com group. The 9 slot is much more useful (and terminated).

boards:s100:backplanev4:start [RetroBrew Computers Wiki]

retrobrewcomputers.org retrobrewcomputers.org
Todd Goodman has the board in stock, see https://www.retrobrewcomputers.org/doku.php?id=boardinventory Todd also had connectors at one time, I'd ask him as the price thru Digikey or Mouser has just gone up significantly. I also have some 3D printer .stl files that were sent to me (not my design) of a very nice card cage for that backplane. I'm happy to send them along.

Another nice option for an IMSAI/Altair clone is Josh Bensadon's board.

S100 Computers - 8080 CPU Board

S100 Computers
s100computers.com

- Gary
 
Hugo Holden said:
think of exact clones of the boards is that all the manufacturer data, software/firmware
Click to expand...

Hi,

A small team of us has been working on a reproduction SciTonics Real Time Clock board for the S-100 buss (Altair's, IMSAI's etc.) We hope to have the boards completed within a few weeks. Much of the test software is available for download on my CBBS when the CBBS is not involved with testing. Hopefully, CBBS will be up 24/7 again in another day or two.

We are planning to have the Reproduction SciTconic RTC board files soon so anybody can just send the design to fab, and get a board back quickly to build and use. For us, this is a hobby, not a business. Hopefully, Todd or Gary will also carry these reproduction boards too.

Yes, with a new computer, the CBBS team has created and tested running CBBS using an Altair 8800c computer with an external modem connected to Port 1 of the 88-2SIOJP board, and a J.A.I.R. based computer with a PMMI modem and hopefully soon, with an external modem hanging on the COM2 port.
Currently I'm posting "Canned Software Kits" on my website to help others have the historic CBBS running on their computers with similar hardware setups.
https://www.brainless.org/Altair/BBSes.html


All this and other work can be found in the https://groups.google.com/g/s100computers group too.



.
 
Got off the phone a bit ago, and my case is now on order from Mike.

I'll need to track down contact info for Todd, and get the 9 slot backplane ordered - I like options! Found Todd's email; inquiry sent!

A lot of the pieces are now on order, but not yet everything required to build a functional system. We'll get there!

-Kevin
 
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The bits I've ordered so far have arrived.

2 x CPU circuit boards
2 x CPU board components
1 x 4 slot backplane and connectors
1 x 9 slot backplane
Front panel board set and switches
Case

I need to put together a BOM for the front panel boards, as well as the 9 slot backplane, and get those ordered. Also need to order power supplies.

I'm thinking I'm going to use the 4 connectors I have and partially populate the 9 slot backplane, and use that. I'll hang on to the 4 slot board.

-Kevin
 
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