Thank you!!! I've been hoping to build one of these front panels pretty much from scratch and I've been wondering how they managed to implement the examine , examine next and the load and load next. I've been looking for this explanation for several weeks! Much appreciated!
@@IMSAIGuy hadn't even thought about the switches. I thought they'd be easy to find. I'll actually do this with a Z80 not the original processor as Z80's are still easy to get and they're a superset of the 8080 instruction set. I'm actually a software guy with a couple years of high school electronics from back in the 70's so I may be getting in way over my head but I have lots of time and parts are cheap. cheers!
@@IMSAIGuy I've been reading through Steve Ciarcia's book on building your own Z80 computer and he talks about the additional chips needed to support an 8080 machine. This book is what sent me down the Z80 path. He also provides schematics for a front panel but its driven by a software monitor program. Which is certainly more functional that the hardware front panel but I'm partial to the binary switch flipping panels of the ALTAIR 8800 and the IMSAI 8080. Call me masochistic. I have absolutely no plans to build the power supply describes in Steve's book. It's an old style linear supply which is what you would expect from a book written in 1981. I plan to use a modern switching power supply and I think with the Z80 5V is all I need. I don't think I'll need 12 or 16 volts for anything. Thanks for the link! Upward and onward!
Everyone: The MPU-A schematic shown here is correct, but BE FORWARNED that the first IMSAI FRONT PANEL schematic shown in this video, which is the last original IMSAI CPA REV 4 schematic, is WRONG. Do not ever use it. The original IMSAI CPA rev.4 schematic has several errors as follows: 1. (Lower Left corner): S-100 bus pin 37 leading to U11 pin 9 is mis-labeled. It should be S-100 bus pin 39 2. (Center Upper Left): U15 pin 1 (SOUT) is shown going up to U25 pin 5. Change the drawing to show U25 pin 5 connected to U15 pin 2 (SOUT*) The second NICE color schematic of the CPA in this video was re-drawn in 2014 by Josh Bensadon has all of the corrections, use that one: s100computers.com/My%20System%20Pages/8080%20CPU%20Board/IMSAI%20CPA%202014.pdf
Thank you!!! I've been hoping to build one of these front panels pretty much from scratch and I've been wondering how they managed to implement the examine , examine next and the load and load next. I've been looking for this explanation for several weeks! Much appreciated!
have you found good switches to use? that was the hard part in my mind
@@IMSAIGuy hadn't even thought about the switches. I thought they'd be easy to find. I'll actually do this with a Z80 not the original processor as Z80's are still easy to get and they're a superset of the 8080 instruction set. I'm actually a software guy with a couple years of high school electronics from back in the 70's so I may be getting in way over my head but I have lots of time and parts are cheap. cheers!
www.s100computers.com/My%20System%20Pages/Mini%20FP%20Board/Mini%20FP%20Board.htm
I never learned the Z80 instruction set. much more than the 8080. lots of indirect addressing. Z80 is much easier hardware wise.
@@IMSAIGuy I've been reading through Steve Ciarcia's book on building your own Z80 computer and he talks about the additional chips needed to support an 8080 machine. This book is what sent me down the Z80 path. He also provides schematics for a front panel but its driven by a software monitor program. Which is certainly more functional that the hardware front panel but I'm partial to the binary switch flipping panels of the ALTAIR 8800 and the IMSAI 8080. Call me masochistic. I have absolutely no plans to build the power supply describes in Steve's book. It's an old style linear supply which is what you would expect from a book written in 1981. I plan to use a modern switching power supply and I think with the Z80 5V is all I need. I don't think I'll need 12 or 16 volts for anything. Thanks for the link! Upward and onward!
Everyone: The MPU-A schematic shown here is correct, but BE FORWARNED that the first IMSAI FRONT PANEL schematic shown in this video, which is the last original IMSAI CPA REV 4 schematic, is WRONG. Do not ever use it. The original IMSAI CPA rev.4 schematic has several errors as follows:
1. (Lower Left corner): S-100 bus pin 37 leading to U11 pin 9 is mis-labeled. It should be S-100
bus pin 39
2. (Center Upper Left): U15 pin 1 (SOUT) is shown going up to U25 pin 5. Change the drawing to
show U25 pin 5 connected to U15 pin 2 (SOUT*)
The second NICE color schematic of the CPA in this video was re-drawn in 2014 by Josh Bensadon has all of the corrections, use that one:
s100computers.com/My%20System%20Pages/8080%20CPU%20Board/IMSAI%20CPA%202014.pdf