{"id":24,"date":"2023-07-06T04:16:48","date_gmt":"2023-07-06T04:16:48","guid":{"rendered":"http:\/\/the-planet.org\/?p=24"},"modified":"2025-10-28T00:55:41","modified_gmt":"2025-10-28T00:55:41","slug":"reproduction-altair-and-imsai-boards","status":"publish","type":"post","link":"http:\/\/the-planet.org\/?p=24","title":{"rendered":"Reproduction Altair and IMSAI Boards"},"content":{"rendered":"

Altair and Imsai Reproduction Boards are now available<\/strong><\/h1>\n

I have the CPU boards posted on Ebay for sale at $40 each + shipping, and sell them directly for $35 + shipping as I avoid Ebay Fees and pass the savings along.\u00a0 My ebay ID is “the-planet”\u00a0\u00a0 \u00a0\u00a0 <\/strong><\/p>\n

I can be reached via Email at gkaufman<aT>the-planet<D0T>org<\/strong><\/p>\n

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Many original Imsai and Altair computers are missing the original boards, or have boards that are in poor condition.<\/p>\n

Thanks to the hard work of many folks, it is now straight forward to restore these amazing systems.<\/p>\n

I was interested in creating realistic replicas of the original 8080A CPU boards.<\/p>\n

Some useful sites to visit:<\/strong><\/p>\n

Michael Douglas www.deramp.com<\/a>\u00a0 Also view his well done video New 8800 “C”<\/a><\/p>\n

Martin Eberhard (88-2SIOJP, also available thru www.deramp.com<\/a>)<\/p>\n

Jonathan Chapman\u00a0 www.glitchwrks.com<\/a> who has done amazing reproductions of S100 and OSI boards<\/p>\n

Josh Bensadon<\/span> JAIR Board<\/a> who has a very well done 8080A cpu single board replacement that interfaces with Imsai and Altair systems.<\/p>\n

John Monahan http:\/\/s100computers.com\/<\/a><\/p>\n

Surprisingly most parts are actually quite easy to locate.\u00a0\u00a0 One of my favorite vendors is Unicorn Electronics http:\/\/www.unicornelectronics.com\/<\/a><\/p>\n

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I arranged to have an original Altair 8800CPU Revision 1 , Altair 4 slot Backplane and IMSAI MPU-A Rev-4 CPU boards scanned to Gerber files thru Gardien Services.<\/p>\n

My goal in this project was to make available a close replica of the original boards.\u00a0 The reproductions are true to the original design and can be constructed using the original manuals.<\/p>\n

Altair 8800 CPU Board Reproduction<\/strong><\/h2>\n

The constructed board below was built up by Martin Eberhard.\u00a0 It was a prototype board that did not have the gold plating that was on the final board.<\/p>\n

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Altair CPU Manual:<\/strong>\u00a0 ALTAIR 8800 CPU Manual<\/a><\/p>\n

Larger Images of Board:<\/strong>\u00a0 Altair Front<\/a>\u00a0 Altair Rear<\/a><\/p>\n

The boards are a very close copy of the vintage board.\u00a0 The CPU boards have been produced with hard gold plating on the fingers and a matte green finish that is similar to the original board.\u00a0 A small mark has been placed on the rear of each to indicate they are a reproduction so they are not passed off as an original in the future.<\/p>\n

The Altair board that was reproduced is a “REV-1”.\u00a0 The only differences I am aware of are that there are duplicated holes for C4\/C5 and an additional hole to connect to S100 bus pin 20 (unprotect).\u00a0 The Altair CPU board was produced at various times with or without solder mask – and with or without gold edge plating.\u00a0 The reproduction has both solder mask and hard gold plating on the fingers\u00a0 for better reliability.<\/p>\n

Imsai MPU-A 8080 CPU Board Reproduction<\/strong><\/h2>\n

The constructed board below was a prototype board that did not have the gold plating that is present on the final board.<\/p>\n

\"\"<\/a>\u00a0 \"\"<\/a> \"\"<\/a><\/p>\n

IMSAI CPU Manual:<\/strong> IMSAI MPU-A CPU Manual<\/a><\/p>\n

Larger Images of Board:<\/strong>\u00a0 Imsai Front<\/a>\u00a0\u00a0 Imsai Rear<\/a><\/p>\n

The boards are a very close copy of the vintage board.\u00a0 The CPU boards have been produced with hard gold plating on the fingers and a matte green finish that is similar to the original board.\u00a0 A small mark has been placed on the rear of each to indicate they are a reproduction so they are not passed off as an original in the future.<\/p>\n

Altair 4 Slot Backplane Reproduction<\/strong><\/h2>\n

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Original Backplane pictured above in my Altair has only 2 slots populated.<\/p>\n

The reproduction pictured below is a very close replica.<\/p>\n

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Larger image of backplane above:<\/strong>\u00a0 Assembled<\/a>\u00a0 Unassembled<\/a><\/p>\n

Link to STL Files to 3D print the edge connectors<\/a><\/p>\n

The Altair 4 slot backplane was produced using double thick PC board material (3.2mm).\u00a0 The original backplanes were produced in both standard PC board material (1.6mm) and the thicker (3.2mm) style.\u00a0 I have the thicker boards in stock, which are much sturdier.<\/p>\n

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Altair 4 Slot Backplane Manual:<\/strong> ALTAIR Backplane Manual<\/a><\/p>\n

PC Board is $35 each (thick\u00a0 PC board material).<\/p>\n

The correct S100 connectors are Sullins EBA50DRTH and are available thru Digikey and other vendors.\u00a0 They use a narrow footprint which is different than many other S100 connectors.<\/p>\n

Shipping is at cost, at the USPS priority mail letter rate for a bare backplane PC board, or the padded envelope rate for board + parts (in USA).<\/p>\n

The side \/ edge connectors can be 3D printed thanks to STL files for a wonderful\u00a0Reproduction<\/a> posted to the AltairComputerClub group on Yahoo by Eric Dale (Thanks!).\u00a0\u00a0 I’d prefer that folks print them locally as they take me about 1 hour each.\u00a0 If you can’t print them locally I will provide them for $3 each with the purchase of a PC board (printed from Blue ABS which looks very much like the original).<\/p>\n

Finally….<\/p>\n

A special thanks to the generous assistance of Santo Nucifora (who loaned me a blank Altair 8800 CPU board) Jonathan “Glitch” Chapman (who cleaned up Gerber files and built up the IMSAI prototype, Martin Eberhard (who built up the Altair Prototype), Al\u00a0 Kossow (who hosts tons of literature on\u00a0Bitsavers<\/a> and sold me my Altair 8800) John Monahan (www.s100computers.com<\/a>) who has extended the S100 bus to support everything from 80486 processors to FPGA and Arduino boards, and many many others!<\/p>\n