Third and final attempt at the Altair project

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Postby bugman » Aug Mon 24, 2009 6:14 pm

Thought I'd post some comments on what I think would be neat to achieve with the altair project. I came accross the A.P.E. project which uses the PC to emulate a floppy disk system in order to boot CP/M. It only requires a 32k/64k altair with a 2SIO card. I wonder if this box would be able to interface with that since it does have emulated serial ports?
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Postby Bill Loguidice » Aug Mon 24, 2009 8:41 pm

I wasn't aware APE worked with anything except for Atari 8-bit systems...
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Postby bugman » Aug Tue 25, 2009 6:31 am

Check the site out. It looks very cool. He is planning a revision with enhancements too...

http://frankbarberis.tech.officelive.com/default.aspx
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Postby Bill Loguidice » Sep Wed 02, 2009 2:03 pm

bugman wrote:Check the site out. It looks very cool. He is planning a revision with enhancements too...

http://frankbarberis.tech.officelive.com/default.aspx


That's right, thanks. I vaguely remember having a problem with the name, since it was already taken and long in use by this: http://www.atarimax.com/
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The Altair Project.. How are we coming along?

Postby Aaron Teeling » Sep Fri 18, 2009 8:06 am

Vince,

I'm sure you have been busy. Any more work being done on the Altair?

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Postby vbriel » Sep Fri 18, 2009 2:19 pm

Well, I got stuck on the 085 single-step, so I'm there right now. If I can't get it to single step, I'm going back to the u-controller to emulate the 8080 and have external RAM to load and run Basic.
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Postby vbriel » Sep Sat 19, 2009 8:46 am

Ok, here's what I decided to do. Because this project needs to GET DONE, I'm going to actually use a 8080. I can single-step the 8080 and this allows the exam/exam next dep/dep next to function.

I will use a charge pump for the voltages to pump 5V up to 12V and then using a 555 I will invert the 5V for the 8080.

Control will be done via ATMEGA8515 so that depending on how the AUX switches are set maybe I can preload basic so you don't have to load it via boot loader. Or just the boot loader gets loaded.

The system will have the following specs:

8080A CPU
62256 32K SRAM
27C256 EPROM containing different versions of basic and the boot loader
ATMEGA8515 to handle control panel operations and ROM loading on power up.
6850 ACIA for console communication

This is probably the best solution to get this project done and working and it is actually really close to an actual Altair in hardware, just reduced circuit.

Vince
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Postby Des » Sep Sat 19, 2009 4:32 pm

Excellent!

Please keep us all posted on this one,

very keen to hear more.



thank you
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Postby vbriel » Sep Sun 20, 2009 2:31 pm

Did some work today, I will be out of town this week so I'm trying to do some work now. The design is looking very positive because the 8080 is easier to single-step.

I have the CPU, u-controller, RAM, ROM circuits finished. I have latches for the switches and data bus finished. Switches are finished too.

Next I have to wire up the LED's and and the serial port. After that I'll wire up the charge pump voltage circuits and start to look things over.

Vince
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Postby Des » Nov Thu 19, 2009 5:10 am

Hi Vince

Any updates on the Altair project?
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Postby vbriel » Nov Fri 20, 2009 8:12 am

Hi Des,

No, I had a workshop in Brooklyn I went to last week. I've got over halft the work done, just need to finish it up and get a board ordered.
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Postby kerryp24 » Dec Tue 08, 2009 8:17 am

How goes this project?
I've been watching and waiting for this.
Would love to have one in my computer room.
God... I miss my Altair!!!
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Postby vbriel » Dec Thu 24, 2009 9:49 am

Ok, had time to work on this project. Man, the CPU choice is killing me. I'm taking the plunge on doing a board layout right now using a Microcontroller to emulate the 8080CPU and display panel. I already did this in the first version I did. The difference is I'm going to use external RAM for memory (32K) so you can run BASIC on it. I'm also going to take advantage of the EEPROM on the micro-controller to store 4K BASIC and then auto load it on power up.

I never got far testing my 8080 emulation so a lot of work will be needed there. I'm finishing schematics now and will work on board layout next so I can get this to the board house.

Just to note, the only reason I decided to stay away from actually using an 8080 is the multi voltage requirements. To generate multiple voltages from a single source was requiring too many components.

Please understand that I am CEO, Senior Engineer, Shipping mangager and many other titles in this small company. When things get busy, I have to focus on filling orders before I can play with my design software. Nobody wants the Altair project going forward more than me. I have several variations of this project to fit everybodys needs when it is done. My focus in 2010 is to have it FINISHED!

Stay tuned, things are looking good.

Vince
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Postby vbriel » Dec Sun 27, 2009 7:50 am

I had time to work on the Altair project this weekend. I have a board layout almost ready, need a part to verify fit of the component. After that I'll order a prototype and go from there.

Vince
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Using a Z80 (or a derivative chip)

Postby sje » Dec Tue 29, 2009 8:51 am

While it may be true that some very early 8080 Basic interpreters had problems running under a Z80, these problems could be fixed by patching. And that's what the early Z80 users did back in the 1970s.

If I can recall correctly, the only incompatibility of note was a slight difference with condition code flag calculation, and a patch was available.

If I were doing this project, I'd use a Z80 derivative that includes all the original Z80 functionality plus lots of extra features like additional opcodes and 24 bit addressing. I'd also use a fast AVR or similar microcontroller to run the boot process and the front panel display/control.
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