Altair 8800 mini-clone up for grabs

Hackerspace
#1

Hey guys, I have an Altair 8800 clone that I put together a number of years ago. It boots and runs a BASIC image from an SD card. I was not able to get CP/M running on it for Zork, and I moved on to other projects.

Original info here: http://www.brielcomputers.com/wordpress/?cat=18

Comes with a PS/2 Keyboard for control and power supply, has a TV and VGA output. Hardware is emulated on a Parallax Propeller, but front panel is fully functional.

It would be nice to recover a few bucks for this, maybe $40 or so?

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#2

I would like that please. I’ll bet I can get CP/M to run.

I’ll probably be at The Space next on Friday for the Member Meeting/Potluck.

#4

It was cloned: the front panel in hardware, the architecture in software. It even has an S100 (ish?) expansion bus inside.

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#6

This is what I get for being out of town.

I’m building an S-100 system and went on a road trip to pick up 4 8" floppy drives… just got home.

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#7

You got a link or is this a homebrew?

#8

Homebrew!

I have an N8VEM backplane, a Wameco 8080 CPU board, and a couple of California Computer Systems cards - memory and serial/parallel interfaces.

I have to figure out a front panel and a monitor ROM.

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#10

Pulled the trigger on this one since the backplane has a slot specifically for this card.

I have to still find switches worth of it… and +8v, +16v, and -16v power supplies.

Once I put the backplane together and find power supplies I need to build a case for it.

Edit: Here’s more info on the front panel card: http://www.s100computers.com/My%20System%20Pages/Mini%20FP%20Board/Mini%20FP%20Board.htm

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#11

I have the backplane built as far as I could get it with the parts I had here in the shop and that Jim Tanner has at his place. I have to order a few things to finish it out and hope to do that today or tomorrow.

I did at least hook it up to my Tektronix power supply and fed it +8, +16, and -16v to verify the LEDs were installed correctly and that the voltage regulator was working. I had to adjust one of the 20k resistors down to 1k to fix the brightness on the -16v power indicator LED. Not sure why they went with such a high resistance.

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#12

If you need help bringing CP/M up on it, I have done CBIOS work in the past.

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#13

Thank you again, Daniel.

The good news:

  • It is a really nice little box.
  • I have never used an Altair, being an IMSAI guy, but they are similar enough that the front panel makes sense.
  • The video VGA port and PS/2 keyboard port emulate a terminal connected to an ACIA at I/O addresses 10H and 11H.
  • It appears the binary files on the SD card are just raw memory dumps. I will try to load my own assembly language programs that way.

The bad news:

  • An add-on memory and disk emulator card is needed to run CP/M so I will have to find one somewhere. The Briel web site seems to indicate they do not have any more.

For grins, I tried this program:

 0000 21 0018	     [10] 00001		lxi	H,Hello	; Point to message
 			  00002
 0003			  00003	Loop
 0003 7E	      [7] 00004		mov	A,M	; Get a character
 0004 B7	      [4] 00005		ora	A	; Is it the end?
 0005 CA 0017	     [10] 00006		jz	Done	; Yes
 			  00007
 0008 47	      [5] 00008		mov	B,A	; Save the character
 			  00009
 0009			  00010	Wait
 0009 DB 10	     [10] 00011		in	10h	; Get port status
 000B E6 02	      [7] 00012		ani	2	; Transmitter ready?
 000D CA 0009	     [10] 00013		jz	Wait
 			  00014
 0010 78	      [5] 00015		mov	A,B	; Recover the character
 0011 D3 11	     [10] 00016		out	11h	; Write the character
 0013 23	      [5] 00017		inx	H	; Point to next character
 0014 C3 0003	     [10] 00018		jmp	Loop	; Repeat
 			  00019
 0017			  00020	Done
 0017 76	      [7] 00021		hlt		; Stop
 			  00022
 0018 48656C6C6F20776F	  00023	Hello	db	'Hello world.'
 0020 726C642E

with this result:

20180811_051009
20180811_051009.jpg2307×1730 1.89 MB

If I flip the AUX switch on the front panel and step through machine code, the monitor displays detailed information!!! If only it was this good with the original…

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#14

So glad you have the time and motivation to get this gear to do something!

Yeah, it’s a shame about the disk, although it might be possible to make your own (with some trouble) if you’re so inclined:

http://www.brielcomputers.com/phpBB3/viewtopic.php?f=23&t=1683

http://www.brielcomputers.com/files/Altair_RD_4.pdf

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