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Thread: Netronics Explorer 85

  1. #1
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    Default Netronics Explorer 85

    I finally got one of my holy grails.. an Explorer 85 in the actual Netronics chassis. It fires up and the monitor seems to work fine.

    It appears to have the BASIC ROMs installed.. starting at C000. However, BASIC will not run. And in looking around I discovered the RAM contents of different address ranges are all the same. So 0000 to 0FFF is same as 1000 to 1FFF, C000 to CFFF and so on.

    Does anyone know if the BASIC Netronics supplied required RAM expansion boards to be installed?

  2. #2
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    How are you keeping. I still owe you an email don't I!

    The information I have found at https://worldradiohistory.com/hd2/ID...-Page-0081.pdf implies that the MS BASIC ROM requires levels B, D and E to be implemented. Level D provided for 4K RAM and level E stated that 'up to 12K RAM expansion could be available'. It doesn't state that the additional RAM was required for BASIC to operate.

    I assume you have the manuals? If not, they are available here http://www.hartetechnologies.com/manuals/Netronics/ (but not the MS BASIC). Still looking for that.

    Early static RAMS did exhibit consistent power-up contents - so I wouldn't worry just yet about the RAM contents. Do you have the onboard debug monitor working? If so, you can write and read unique values into the memory to see if they are OK or not.

    There is a cheap and cheerful memory test program available somewhere to test for things like this.

    EDIT: https://github.com/TomNisbet/Simple8...opelec1081.pdf states 'MS BASIC in ROM and a minimum of 4K RAM'. The 4K (I assume) must start at $0000.

    Dave
    Last edited by daver2; October 26th, 2020 at 03:46 AM.

  3. #3
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    I am keeping well, all things considered. Trust same for you? And you don't owe me anything! But I very much appreciate your help and insight for stuff like this. I did end up dumping 'the other half' of that 1702 EPROM for the Microkit machine - if it helps any. I wondered if you were able to 'decrypt' it. But there's no rush on that - not like we have software. I actually purchased a 1702 reader/writer kit and have been working on that intermittently so that might give better results anyway.

    Yes I am thinking you are correct. IIRC if I have 8x2114s then I have about 4K of RAM, but perhaps it is not strapped the right addresses? I wonder if I could use my ProcTech 8KRA board... it is configured to start at $0000 - but I don't know how interchangeable S100 gear is - it was set up for my SOL 20.

  4. #4
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    And yes, I can use the monitor and attempt to edit memory contents but at $0000 and most ranges I've tried I cannot actually edit anything. I'm still trying to figure out what address space is available.

  5. #5
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    The default 256 bytes of RAM is at $F800 to $F8FF.

    The monitor uses from $F8DC upwards, meaning that $F800 to $F8DB is available for you to use.

    To modify some user memory:

    .IF800
    01
    02
    04
    08
    10
    20
    40
    80
    00
    55
    AA
    FF
    <ESC>

    To dump the memory back:

    .DF800,F81F

    Check for equality as to what you entered.

    Can you identify the revision of your Motherboard and any other boards you have in the system?

    Can you also provide me with the settings for SW200 and SW201.

    SW200 is for the EPROM base, SW201 is for the RAM base address.

    SW201 settings seem to be dependent upon the revision of the PCB...

    How are you attempting to start BASIC?

    When you start BASIC, do you get the Microsoft Copyright notice or not?

    EDIT: So I tracked down an interesting project at https://github.com/TomNisbet/Simple8085 giving me some clues as how to run BASIC.

    Enter the following commands via the monitor:

    .XS nnnn-F880 nnnn-C000
    .G

    Where nnnn is the current value of the Stack Pointer (SP) and Program Counter (PC) respectively. F880 sets the initial SP to the highest location within the original 256 bytes of RAM and C000 is the entry point of BASIC (Cold Start).

    At this point, BASIC should ask for the memory size.

    To achieve the correct ROM decode, links 1, 4 and 5 should be IN and others OUT at SW200.

    For RAM at $000 then SW210 should be either 8, 5, 4 and 1 IN (Revision B or below) *** OR *** 8, 5, 3 and 1 IN (Later than Revision B - Revision 5 Motherboard?).

    You should also be able to dump memory from the start of the BASIC ROM (.DC000,C020). I would bet that the first instruction should be an unconditional Jump ($C3).

    Dave
    Last edited by daver2; October 27th, 2020 at 03:44 AM.

  6. #6
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    I have found a picture at https://github.com/TomNisbet/Simple8...explorer85.jpg.

    This has SW200 as 1/4/5 IN/ON (ROM at $C000 as expected).

    But has SW201 as 1/4/6/8 IN/ON for the RAM decode?

    What are your switches/links set to and revision of board (as asked in my previous post)?

    Dave

  7. #7
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    Thanks Dave.

    The revision of my board is D.

    I can edit memory contents in the space you mentioned.. just not anywhere else.

    Interestingly, SW200 and SW201 are all set to off.

    https://drive.google.com/file/d/1du7...ew?usp=sharing

    I did attempt to start BASIC using the instructions you mentioned - actually found a screenshot of someone else starting BASIC with similar commands, but when I do the G command it just freezes in place. No prompt ever happens.

  8. #8
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    Ah ha...

    SW200 / SW201 being all off is no good...

    I can't see a combination of SW200 (ROM base address) and/or SW201 (RAM base address) where all links being out (switches OFF) are a valid combination.

    I can't see your google drive at the moment (I am at work) but I will look when I get back to my home machine...

    You might want to try changing SW200 to 1, 4 and 5 ON only and SW201 to 1, 3, 5 and 8 ON only. This is based on the documentation I provided a link to back in post #2.

    This should put the ROM at $C000 to $DFFF and the on-board 4K ram at base address $0000.

    Level D Assembly manual for the configuration of SW201 (RAM).

    Level E Assembly manual for the configuration of SW200 (ROM).

    I see there are a few track cuts and wire links in the manuals to add the RAM. It may also be worth double-checking that all is well here and you haven't got any missing wires that have come adrift in the 30/40 years since this machine was last used!

    Note in an earlier post (as I can't now edit it) I incorrectly referred to SW201 as SW210...

    Dave
    Last edited by daver2; October 27th, 2020 at 12:36 PM.

  9. #9
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    At home now !

    COVID-19: Work = spare bedroom (work IT - personal emails and file sharing sites forbidden). Home = downstairs on my Mac...

    That picture is no good if you want to run BASIC...

    Dave

  10. #10
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    Okay so I set the jumpers both ways you mentioned above... but yeah.. no change.

    I decided just to do some perfunctory checks and verified the ROMs with my EPROM programmer using known good dumps of the BASIC from the hartetechnologies site. They verify 100%.

    One thing I'm curious about though - when I dump C000, I get something that looks quite different from what the EPROM shows. I'm not sure if when looking at the EPROM I treat offset 00000000 as C000, but if I do, 0000000-0000000F reads like this:

    F3 C3 04 C0 11 D3 C2 06 52 21 00 01 1A 77 23 13

    But dumping C000 to C00F on the computer itself, I get:

    C3 03 F0 3E 8D D3 F2 3E 09 32 F8 F8 D3 F8 AF 32

    Think it should read the same as the reader has it no?

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