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Sol-20 Reproduction

I am making a full sized Sol-20 reproduction, the first fully assembled microcomputer with a built-in keyboard and television output.

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The Sol-20 was an interesting machine. It was introduced in July 1976, appearing on the cover of Popular Electronics magazine. With its 8080 microprocessor and S-100 bus, it had more in common with the Altair 8800s and IMSAI 8080s of the day, than it did with the Apple and Commodore computers that were soon to follow, despite looking more like the latter.

I distinctly remember seeing a Sol-20 in the wild. It would have been the fall of 1977 or perhaps the summer of 1978. I had just started at the University of Waterloo and was visiting my cousin in Toronto. While walking along Queen Street we passed a small computer store and the Sol was prominently displayed in the front window. What a great looking machine with it's bright blue case and walnut sides, but at roughly $1650 (CAD) it was out of my poor student price range.

Because only 12,000 were ever produced, Sol-20s are virtually unobtainable today, so I guess I'll have to build one. Talk about delayed gratification.

The Game Plan

So my plan is to make a full size case that will be as authentic looking as possible, with beautiful walnut sides for sure. I will 3D print the blue panels instead of using sheet metal so the build will be accessible to more people should they decide to make one.  

For the keyboard I have been in touch with Dave from osiweb.org who has designed a complete replacement keyboard for the Sol-20 using modern Cherry key switches. From the Unified Retro Keyboard Project:

The keyboard is not a replica of the original. It doesn't use the same capacitive circuit or keys. But it does have exactly the same layout with the same functionality, including the 3 LEDs (UPPER CASE, SHIFT LOCK, LOCAL) and 3 outputs (RESET, BREAK, LOCAL). It uses cherry MX or Futaba MD-4PCs keys. Neither has quite the same feel as the capacitive keys, but the Futaba keys approach the travel of the keytronic switches, and do have a nice feel.

I'm getting the keyboard as a kit and looking forward to putting it together.

On the inside I'm going to emulate the Sol-20 hardware on a Raspberry Pi 4. To that end I have a working (very basic at this point) Python based emulator I'm going to post to GitHub shortly. 

I haven't decided what to do for a monitor yet. Certainly a CRT of some sort would be ideal, but I may have to go with a LCD.

All Things Sol-20

Normally when I undertake a reproduction project like this, I spend a lot of time on the internet researching my intended target. Usually the information I need is scattered across many sites and is often hard to find. Not this time though.

Jim Battle has done an amazing job of gathering a huge treasure trove of Sol-20 materials into one site. A one stop shop for the would be Sol-20 replicator, or anyone with an interest in this wonderful retro computer.  Not only that, Jim created a great Sol-20 emulator Solace which stands for Sol Anachronistic Computer Emulation. I especially like his virtual cassette interface.

With much attention to detail it faithfully simulates reading tapes at either 300 or 1200 bits per second and will complain if data was "saved" at 300 and you try to read it back at 1200 :-)  Of course you can turn these "features" off.  Very cool.

Thanks Jim for all your hard work. 

Is Emulation the Sincerest Form of Flattery?

While I was researching the project and planning the build I was working a Sol-20 emulator. I thought about using Jim Battle's Solace emulator, but it is Windows based and ultimately I hope to run my Sol-20 reproduction on a Raspberry Pi 4. 

Since the Sol-20 was based on the Intel 8080 microprocessor I thought that would be the logical place to start. Fortunately for me, Space Invaders and some of the other early arcade machines also used the 8080.  Because there is a very active gaming community helping to preserve these retro classics, there are a number of great 8080 emulators to be found on GitHub.  I ended up cloning py8080 because it's Python based and I'm more comfortable right now with Python than I am with C++.

So with a working virtual 8080 processor it was a pretty easy task to allocate some memory for it (64K because why not), load a monitor program (Solos since it was the default shipped), set the instruction pointer to the start of the program (0xC000), and run the emulator. Success! Technically I had a Sol-20 running in emulation, but it was pretty boring since I had no way to interact with it. Time to create some virtual devices.

The Display

The system memory used by the Sol-20 is as follows:

C000-C7FF - System ROM. Sol-20 "Personality Modules" like Solos are mapped here.
C800-CBFF - System RAM. Reserved by the system.
CC00-CFFF - Display RAM. Shared memory between the CPU and VDM-1 video circuit.

Although most systems shipped with only 8K or 16K of memory (or less) in those days,...

Read more »

  • Soft Switches

    Michael Gardi3 days ago 0 comments

    The Sol-20 had 4 banks of DIP switches on the motherboard to control various aspects of the machine's operation. Here's a photo of three of them. 

    I didn't see an advantage to using physical switches for my emulated hardware so I created a configuration file instead.

    # SOL-20 SWITCH FUNCTION DEFINITIONS
    #
    # This configuration file replaces the four physical setup switch banks on the Sol-20.
    #
    # Display Control
    #
    S1-1 = 0   # 0-Run  1-Restart to Zero.  (N/A for emulator.)
    S1-2 = 0   # Not used.
    S1-3 = 0   # 0-Show control characters. 1-Blank control characters (ASCII values < 32).
    S1-4 = 0   # 0-Colored characters on black background. 1-Black characters on colored background.
    S1-5 = 0   # 0-Solid or NO cursor. 1-Blinking cursor. (NOTE: Requires apscheduler - "pip install APScheduler")
    S1-6 = 1   # 0-Blinking or NO cursor. 1-Solid cursor.
    S1-7 = 0   # 0-White screen. 1-Green screen. 2-Amber screen. (Emulator extension.)
    S1-8 = 0   # 0-6574 character ROM. 1-6575 character ROM.     (Emulator extension.)
    #
    # NOTE: No cursor if S1-5 and S1-6 are off at the same time.
    #
    
    #
    # Sense Switch
    #
    S2-1 = 1   # Sense switches in LSB to MSB order. Read by the system with an IN 0xFF instruction.
    S2-2 = 1   # Not used by many applications.
    S2-3 = 1
    S2-4 = 1
    S2-5 = 1
    S2-6 = 1
    S2-7 = 1
    S2-8 = 1
    #
    
    #
    # Serial I/O Baud Rate Switch
    #
    S3-1 = 0   # 1-75 Baud.
    S3-2 = 0   # 1-110 Baud.
    S3-3 = 0   # 1-150 Baud.
    S3-4 = 0   # 1-300 Baud.
    S3-5 = 0   # 1-600 Baud.
    S3-6 = 0   # 1-1200 Baud.
    S3-7 = 0   # 1-2400 Baud. 2-4800 Baud. (Emulator extension.)
    S3-8 = 0   # 1-9600 Baud.
    #
    # Do not turn on more than one switch at a time.
    #
    
    #
    # Serial I/O Control Switch.
    #
    S4-1 = 0   # 0-Parity even if S4-5 set to 1. 1-Parity odd.
    S4-2 = 0   # Data word length.  | 0        | 1         | 0         | 1
    S4-3 = 0   #                    | 0-8 Bits.| 0-7 Bits. | 1-6 Bits. | 1-5 Bits.
    S4-4 = 1   # 0-2 stop bits(1.5 if 5 bit words). 1-1 stop bit.
    S4-5 = 0   # 0-No parity. 1-Parity.
    S4-6 = 0   # 0-Full duplex. 1-Half duplex. (N/A in Emulator)
    #
    

    This file switches.cfg is loaded when the emulator starts up, so if you make any changes to the file you will have to restart the emulator to pick them up. I have posted this file and the updated code that implements these changes to github.

  • Interfaces

    Michael Gardi7 days ago 0 comments

    Here is a photo of the back of an original Sol-20.

    You can see that the whole left side is taken up with power supply components: power button, fan, fuse, and  power cord connection. Since my reproduction does not require any of these I chose to focus on and highlight the interface section in the lower right part of the rear panel.

    So I designed and printed my own "interface" panel and dug through my parts box for the components to populate it.

    I then attached the interfaces panel to the rear panel with glue and braces.

    Then I added the connection hardware. Here is what the back of my reproduction look like.

    Understand at this point these ports are mostly for show. I already have a "virtual" cassette so I'm unlikely to implement a physical one. I do plan to get the serial interface working, but since I have nothing with a parallel interface to connect to, I probably won't wire that one up. While I don't plan to support real Sol-20 personality modules, I do have an idea that I might simulate a personality module with perhaps RFID tags to have the Sol-20 reproduction load different software modules on system startup.  Right now the personality module slot is just a simple hole.  

  • A View Into the Soul of the Sol-20

    Michael Gardi7 days ago 2 comments

    From the beginning of my work on the Sol-20 reproduction I wondered what kind of display I would use with it. Of course a small CRT based TV or monitor would be ideal. To that end I put out feelers with my maker mates and even had someone at a local electronics recycling depot keeping an eye out for me. But after a couple of months and no success I realized I needed a Plan B.

    I started thinking "What if Processor Technology had sourced and branded a monitor for the original Sol-20?". What would that look like? Well it might have looked something like this.

    This design takes its cues from the Sol-20 with the wooden sides and color scheme. It has a retro CRT look while using a period correct 4:3 aspect ratio LCD panel. I my humble and somewhat biased opinion it looks great sitting on top of the Sol-20 reproduction.

    The build for this was pretty straight forward. I started by laying out the side panels in Fusion 360.

    I used the DXF file to laser cut from 1/4 inch plywood two of the smaller side pieces with both sets of holes and two of the larger side pieces with only the one set of holes closest to the center. Using four 1/2 inch wooden dowels cut to 188 mm and with pre-drilled starter holes in the ends I assembled the inside frame (smaller panels) with No. 6 x 1 inch wood screws.

    The larger panels I sanded down and stained with the same Minwax Walnut gel that I used on the Sol-20 sides.

    The funky grain patterns were a bit of a surprise but I'm kind of liking it. I could have used walnut here but balked a bit at the additional cost. Then I attached the outer panels to the inner frame with M3 x 14 mm bolts.

    For the display I repurposed the screen frame that I used in my 2:3 Scale VT100 Reproduction

    I had to tweak the design a bit and I added the logo but overall it saved me a lot of time to repurpose the design. I used the same display as the VT100's a PIM372 (Digi-Key part number 1778-1225-ND), an 8 inch 1024x768 XGA display. 

    Th display panel just snaps into the frame. Be sure to get the orientation right with the display connector at the top of the screen frame. I printed a "caddy" for the driver board and after I connected the ribbon cable attached the board and caddy to the back of the display panel with two sided tape. 

    Next I designed and printed the "skin" used to wrap the monitor.  

    I attached the two pieces with glue and a brace for support.

    Then I wrapped the monitor frame with the skin. If you loosen the bolts holding the larger side panels in place the skin should slide in easily. Then tighten the bolts again to hold the printed panels in place.

    Finally insert the screen frame and display into the monitor.

    I connected the display to the Raspberry Pi with an HDMI cable. I was also able to power the display panel via a micro USB cable from one of the Pi's USB ports. 

    It was fun to imagine an alternate timeline where Processor Technology sold a branded monitor with their Sol-20s. 

  • The InSide Story

    Michael Gardi11/16/2021 at 02:45 4 comments

    The walnut sides of the Sol-20 are beautiful and help to set it apart from all of the other computers of the era. I really wanted to do them justice in my reproduction. I also saw the fabrication of the sides as an opportunity to advance my woodworking skills.

    A couple of years ago I was thinking about building my own CNC router. At that time the The Mostly Printed CNC (MPCNC) was a popular choice. At the same time a friend told me about the Kwartzlab makerspace so I took a tour on one of their Tuesday Open Nights. I saw their massive Mach3 driven CNC router with a 4x4 foot cutting bed, plus their 100 watt laser cutter, complete woodworking, metal fabrication, craft, and electronics shops and decided to join on the spot. The cost of the parts for a MPCNC would pay for a years worth of access to Kwartzlab. I was attracted by the cool tools, but what I didn't consider at the time was all of the great people that I would get to know there.

    Despite the fact that I have had access to the CNC at the "lab" for almost three years now, I have never actually used it. Finally now I had a great reason to remedy that. I had to take some online courses and one-on-one training but eventually I made my first CNC artifact. 

    This of course is a Sol-20 side piece that I cut from a scrap piece of plywood I had lying around. I wasn't about to risk my expensive slab of walnut on my first attempt! But it went well so I took the plunge.

    And thankfully that went OK too. But I was not quite done. The CNC just cut out the side shapes. I wanted to get the nice rounded edges as well. I learned that this was accomplished by using a round over routing bit (pretty clear at this point that I'm not a woodworking guy right). With a little more expert coaching from some lab mates I got this done as well learning how to use a handheld router.

    Finally to finish off the pieces I applied some Minwax Walnut Gel Stain. This couldn't have been easier. The stain is applied evenly to the wood with a brush or rag and after only 3 minutes the excess is removed by wiping it off following the grain of the wood with a rag. 

    This afternoon I installed the walnut sides onto my Sol-20 reproduction.

    So happy with the result.

  • Wiring the Keyboard

    Michael Gardi11/08/2021 at 21:57 0 comments

    The keyboard encoder is expecting 5V while the Raspberry Pi 4 operates at 3.3V. So to overcome this I purchase a Voltage-Level Shifter Module from Amazon. I also printed a "caddy" to hold the Pi 4 in place and added a small 30 mm x 30 mm x 10 mm blower fan for good measure to keep things cool. The fan I used is from Amazon:  GDSTIME 3cm 30mm x 10mm 5V DC Brushless Small Blower Cooling Fan, with Dual Ball Bearings. The fan and the keyboard will be run off of the Pi's power supply. The Pi is secured in place to the caddy with two sided tape.

    I then mounted this unit onto the back support of the Sol-20 frame again using two sided tape. The USB and HDMI ports are facing to the rear of the unit.

    So we are ready to wire the keyboard to the Pi. Here is what the Sol-20 header pinout looks like.

    And the Raspberry Pi level shifter hat.

    So here is how I wired the keyboard. Note that for the exception of +5V and GND lines which are wired to the 3.3V side or the level shifter, all of the other connections are wired to the 5V side.

    Keyboard EncoderRaspberry Pi Description
    5V5VPower
    GNDGND
    D0GPIO6Key 0 bit (low)
    D1GPIO13Key 1 bit
    D2GPIO19Key 2 bit
    D3GPIO26Key 3 bit
    D4GPIO21Key 4 bit
    D5GPIO20Key 5 bit
    D6GPIO16Key 6 bit
    D7GPIO12Key 7 bit (high)
    STROBEGPIO5Key ready on falling edge.
    OUT1GPIO23LOCAL button. Toggle. HI when LED on.
    OUT2GPIO22BREAK button pressed when rising edge.
    OUT3GPIO24RESET button pressed when falling edge.

    Here is what the wiring looks like.

    I'm investigating a BREAK key issue with Dave, but otherwise everything is working great. The keyboard is now integrated with the emulator. Getting close. Very exciting.

  • Mounting the Keyboard

    Michael Gardi11/08/2021 at 21:32 0 comments

    I wired the keyboard up to the Raspberry Pi 4 I will be using to run the Sol-20 emulator. I did enough testing to ensure that all of the keys are working as expected. At first some of the keys were not responding, but with Dave's help I discovered I had missed installing a couple of jumpers and also I found a solder bridge that shouldn't have been there. When I was satisfied all was well I installed all of the keycaps. 

    Using the finished keyboard I was able to refine the measurements for the keyboard cutouts in the front panel. I reprinted the panel with the changes in the "new" light blue filament and reinforced it as I had the first one.

    I added some 1/2" x 1/2" wooded supports for the keyboard on the side frame positioned about 2mm below the top edge that the front panel will be resting on.

    Using the printed front panel as a guide, I positioned the keyboard and locked it in place with four #6 x 5/8 inch wood screws.

  • Keyboard Construction

    Michael Gardi10/27/2021 at 01:00 0 comments

    My Fubata MD-4PCS key switches finally arrived! Time to get the keyboard put together. The first step was to add the 85 IN4148 diodes. To save some time I printed a diode lead bender from Thingiverse.

    I was super careful to double and triple check the orientation of each diode since trying to replace one after all the switches are installed would be very hard.

    You can also see that I have installed the screw-in stabilizers for the space bar and Shift keys plus the three limiting resistors for the Local, Upper Case, and Shift Lock key LEDs. On the back a 2x20 pin female connector was added to mate with the encoder.

    On the aligner PCB there are four extenders to be used with the Spacebar and Shift Stabilizers.

    Snip these off and as the text instructs you have to file down one end so that it is 1.5 mm thick so they will fit into the keycaps. 

    This is how they will be installed when you first start adding switches attaching the aligner and keyboard PCBS.

    Make sure that they pass through the openings in the aligner as pictured above.

    I followed Dave's advice adding the switches.

    • Snap a few Futaba keys into the aligner, perhaps 3 or 4 evenly spaced per main keyboard row, and one at each corner of the keypad.   Then fit the aligner with keys to the keyboard PCB. At this point you should have the extenders connected and ready to go as pictured above.
    • Solder in one lead of each switch.  Then, go through all the switches and reflow each solder joint while applying tight clamping pressure (with your fingers) to push the aligner and PCB together so each switch is flush.  This makes a torsion-box structure for the keyboard.
    • Now solder the second lead of each switch.
    • Now snap in a few more keys, spaced evenly between the already installed switches, and repeat the same procedure as above.
    • Now install the rest of the switches, snapping in enough switches to fill one of the gaps between keys, then soldering all the leads at once.

    Here is what I have so far. The wires you can see on the left had side of the keyboard are for the Local, Upper Case, and Shift Lock key LEDs since I found that the leads on the LEDs that I had were too short.

    Using one of the keycaps I cut the wires so that when the LED was attached it would extend up into the keycap without touching the top when the key was depressed.  Looks like this.

    Finally I attached the encoder via the 40 pin connector.  There were holes on the encoder and keyboard PCBs but I found they did not line up correctly and would have been hard to reach at any rate. So I printed a brace to secure the front part of the encoder board.

    That's pretty much it for the keyboard. I'll attach the keycaps once I have verified that everything is working as expected. 

  • More Skinning

    Michael Gardi10/24/2021 at 16:12 0 comments

    I finished the cover for the back part of the Sol-20. I had to print it in four parts which I glued together and braced.

    If I get another 3D printer it will have a 500 mm x 500 mm print bed for sure. Or maybe I can just get Ivan Miranda to print these large parts for me ;-)

    At any rate the panel fit perfectly on my Sol-20 frame. 

    Seeing more of the light blue convinces me that it's my preferred color choice. 

  • Logo

    Michael Gardi10/23/2021 at 00:42 0 comments

    One of the things that makes the Sol-20 so memorable is the logo bar of yellow/orange lettering that runs the full width of the body.  Stunning. Needless to say I wanted to do a good job of reproducing the logo.

    Again I have to thank redjr16 who sent me a great picture of the logo from his machine.

    With his picture, and knowing the dimensions of the logo (width 446 mm), I brought the image into Fusion 360 as a Canvas and calibrated it within fusion to it's actual size. Using Fusion drawing tools (mostly splines) I "traced" the letters and icon and ended up with a sketch of the logo.

    My plan at this point was to save the sketch as a DXF file, bring it into Inkscape, add the colors, and print the logo onto cardstock which is what was done on the original Sol-20. I even had a piece of acrylic cut to size to go in front of it to protect it, again like the original.

    I have had some success in previous projects "drawing" text by extruding the letters and printing them in a different color by pausing the print at the appropriate layer and switching the filament. So I decided to give this a try. To my delight this worked better than expected.

    The small amount of  relief afforded by the extrude characters makes them really pop. So as not to waste, I am using the acrylic piece as a backing for the printed logo which is only about 1 mm thick. 

    Here is a sneak peek at the logo bar in place. I have only just started printing the top panel.

    You might be asking "Hey Mike what's with the two different blues?". I tried the lighter blue on the top panel and I like it better, so I will eventually be reprinting the keyboard panel to match.

  • Measure Twice...

    Michael Gardi10/21/2021 at 23:51 0 comments

    So I'm working on the blue console piece that extends from the logo to the back of the Sol-20. Having the DXF for the inside panel that this rests on is a big help getting the measurements right, but since the total print time for this piece is 11 hours I really wanted to make sure the fit is correct. So to that end I invested 30 minutes to print a 10 mm slice of this piece just to be sure.

    On the right you can see that the console panel extends a bit past the acrylic plate that covers the logo with a little overhang. On the left it wraps around...oops

    Ironically at this point in writing the log I realized that the curved part at the back was wrong, and should not just follow the inside panel like that. It needed to look more like this:

    So a few tweaks to my model and another 30 minutes of printing and I get this:

     Much better. I feel a lot more confident now kicking off those long prints.

    Maybe I should change the title to Measure Thrice...

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Discussions

llcameron wrote 10/24/2021 at 18:32 point

You're work on this is amazing!  Its great to see the SOL-20 finally get the love it deserves!  I'm hoping you will make kits avaiable so we can build one of these beauties ourselves!

  Are you sure? yes | no

Michael Gardi wrote 10/24/2021 at 20:34 point

Thank you. I’m not sure about a kit, but I will be creating an Instructable with all the steps necessary to make one.

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D2 wrote 10/16/2021 at 00:59 point

all this is awesome.  Well-done, and I’m eager to see your progress. 

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Michael Gardi wrote 10/16/2021 at 04:41 point

Thank you.

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Atsushi Takahashi wrote 10/04/2021 at 17:00 point

I built an S-100 bus computer or two in the early 80s... My friend had an EPROM programmer running on a SOL-20! They were so cool because of the integrated S-100 bus slots and the built-in video and keyboard! Another friend had an IMSAI with the cool blinky light front panel.

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Michael Gardi wrote 10/04/2021 at 23:25 point

Wow. That’s pretty neat. Was the EPROM programmer running on a card in one of the slots or using the serial or parallel ports?

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redjr16 wrote 09/22/2021 at 03:47 point

Did you know that Les Solomon only agreed to publish the article if his name was on it.  Hence Sol-20

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Michael Gardi wrote 09/22/2021 at 14:36 point

From Lee Felsenstein 's account about making the Sol-20: "

And somewhere in the midst of all this I looked up at Bob and said: "Let's advertise it as having 'the wisdom of Solomon."' From the comment came the name Sol, which is meant to be written in biblical-movie-poster letters chiseled out of stone. Les will never live it down. " (Maybe he was just being politically correct?)

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redjr16 wrote 09/22/2021 at 03:43 point

I’ll be following with much interest.  I built the original and it basically helped to launch my  professional career.    I used it for many years and learned a lot.  I even bought a 2nd one.  The original has been boxed up since the late 80s and remains in great condition.  I do not if it will even fire up.  Sadly, the main manual got discarded years ago by accident, and I don’t remember how I booted it.  I know I had a NorthStar disk subsystem attached(floppy of course).  It was a great machine in its day.   Great project Michael. 

  Are you sure? yes | no

Michael Gardi wrote 09/22/2021 at 14:43 point

Thanks for following.  I really like hearing how some of these machines affected the course of people lives in a positive way. 

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Dave's Dev Lab wrote 09/16/2021 at 19:58 point

are the schematics available for the original? i am curious as to how hard it would be to design a modern pcb....

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Michael Gardi wrote 09/16/2021 at 20:36 point

The Sol System Manual has the schematics, PCB artwork, and mechanical drawings. Here is a link to the starting page: 

https://archive.org/details/Sol20SystemsManual/page/n251/mode/1up

Looks like we have @J. Peterson  to thank for them.

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Dave's Dev Lab wrote 09/16/2021 at 20:59 point

ahh dandy! i will have a look!

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Rod Rowley wrote 09/16/2021 at 19:56 point

I have one that i build in '77-'78. Hand assembling programs for it taught me tons.

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Michael Gardi wrote 09/16/2021 at 20:37 point

Just out of curiosity is it still in running condition? I did a fair amount of hand assembly in my day too but mostly 6502 stuff.

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Rod Rowley wrote 09/16/2021 at 22:09 point

I have not even tried to fire it up in 40 years, so i doubt it.  Did you have a little slide rule thingy to tell you the hex codes to enter for the various flavors of the instructions?  I still have mine.

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Michael Gardi wrote 09/17/2021 at 00:26 point

I can remember a well worn paperback size 6502 Assembly Language Instruction manual and of course one of those folded reference cards ;-)

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J. Peterson wrote 09/17/2021 at 23:35 point

The Sol-20s used foam "springs" for the keyboard. Google "Sol-20 keyboard repair". After a decade or two, these usually turn to dust, and need to be replaced. There's also the usual issues with capacitors failing, etc.

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J. Peterson wrote 09/15/2021 at 21:14 point

Built one of the kits back in the day. I scanned in the manual and other documentation at

https://archive.org/details/@j_peterson?and[]=subject%3A%22S-100%22

I recall I really wanted a computer with blinkenlights, so I modified my SOL by cutting away a couple of slots above the keyboard and mounting LEDs behind it. I then cut the edge connector off a proto board, stuck that in the top slot, and used the signals to drive the LEDs. It worked, but probably not ideal for signal integrity on the S-100 bus.

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Michael Gardi wrote 09/16/2021 at 02:27 point

I love hearing stories like this. One of the reasons I like making reproductions. Thanks for sharing.

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Syd Kahn wrote 09/15/2021 at 18:42 point

This is the first microcomputer I ever got paid to program - when no one was wanting to watch the tv that is - the wood sides allowed the hertz out - it radiated like a small star - Had an 8K board in it - a lot for the time - brings back fond memories ...

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Michael Gardi wrote 09/16/2021 at 02:32 point

Thanks for sharing Syd. Not sure if I'll have the same radiation problem with a Raspberry Pi 4 inside. My only memory is seeing a Sol-20 in that computer store those many years ago. Now I'll get a chance to make more memories.

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Andrew Wasson wrote 09/15/2021 at 17:40 point

Cool! I'm more of a CDP1802 enthusiast but I was also drooling over 8080 computers in Popular Electronics / Radio Electronics / ETI / etc... in the mid-late 70's. 

BTW I too have one of Oscar's PiDP-8/Is and I love it. It hangs on my network just waiting for a game of adventure or some old school programming.

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Ken Yap wrote 09/15/2021 at 08:12 point

>Talk about delayed gratification.

I know the feeling. I remember those ads in computer magazines I used to compare and drool over. More power to you, and looking forward to updates.

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Nyles wrote 09/14/2021 at 18:18 point

I have several software manuals for the SOL-20 if you're interested.

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Michael Gardi wrote 09/14/2021 at 20:25 point

I do have PDF copies of the manuals, but I love having the originals if I can get them. What manuals do you have? Of course I'd be happy to pay for shiipping.

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Nyles wrote 09/14/2021 at 22:46 point

User's Manuals, in no particular order:

Music System

Gamepac1

Gamepac2

Extended Cassette BASIC

Cassette PILOT

BASIC/5

ALS/8

SOLOS CUTER

Software #1 Resident Assembler

ASSM 8080 Assembler

DEBUG 8080 Debugger

TREK-80

8KRA

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Peabody1929 wrote 09/14/2021 at 17:11 point

Do you plan to build an exact HW replica or emulate the SOL-20 in SW?  An example would be the PiDP-11.

  Are you sure? yes | no

Michael Gardi wrote 09/14/2021 at 20:31 point

I plan for the case to be as authentic looking as possible, with walnut sides for sure, but I may 3D print the panels instead of using sheet metal so the build would be accessible to more people should they decide to make one. I am going the emulator route. In fact I'll be posting an alpha version of that very shortly. BTW I have one of Oscar's PiDP-8/Is and I love it.

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