Sol First Run

My first attempt at getting software running on my Sol is not encouraging. I believe the Sol is running correctly and loading the software from tape, but the programs do not execute. I loaded the classic game TARG from GAMEPAC 1 and immediately ran into trouble. Here’s a picture of the Sol lab, right in the midst of trouble.





I hooked up a cassette player to my Sol, typed the command “XEQ TARG” and started playing the tape. A couple of minutes later, the tape is done loading, the program runs, and all I get is a memory dump that fills the screen with this:



90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90

90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90

90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90

90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90



This obviously isn’t working right. Perhaps it is time to test my memory boards, I have two 16KRA boards, but let’s keep it simple and just run one board for now. The boards are marked 1 and 2, I installed Board 1 but I just get the same memory dump.

Time to investigate more closely. I wonder what the code looks like loaded in the Sol memory. Sol apps run from the top of memory at Hex 00 00 and can be started with the command EX 0, you are literally executing the code starting at 00 00. I can load the program from tape with the GET command, and then look at memory before I execute. But there’s no data there, it’s blank.

I poked around and found a nice screen shot of a memory dump, if the memory is reset, a dump should show a nice little Hexadecimal pattern of FF 00 FF 00. But when I run DU 00 A0 all I get is FF FF FF FF. Aha, there is no memory at that location.

It appears that the memory board is not mapped correctly, so I’ll have to reset the DIP switches. So it is time to RTFM. The 16KRA manual is a good place to start, there’s a convenient PDF copy at the Sol20.org archives. I reconfigured the switches to run memory at address 00 00, but if I try to write to memory, I can only read FF FF back, it’s not working. I reconfigured and tested the second 16KRA board with similar results. I tested various locations and found some usable memory at C9 00, this appears to be on the motherboard. But I need some memory at 00 00 to run programs from tape.

Well this is disappointing, it is far too much work to get some little 8080A programs running. I will have to determine why the RAM isn’t working, I hope it’s something simple like the power connector problem I solved earlier. I think these old static RAM boards used some higher voltages like 16v that may not be used by the CPU, so maybe there’s just no power going to RAM even if the CPU runs OK. But I don’t have a voltmeter to test the output, I guess I’ll have to buy one.

The First Run of the Sol is a failure, oh well. I think I need to take a break. I think I’ll go fly a kite.

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