SOL-20 memory map

[guibrush]

Hi,
I'm trying to figure out how the SOL-20 works, because I'm going to have access to a SOL-20 equipped with a third-party personality module: the Micro Complex DUAL PERSONALITY MODULE. I don't know if it's working yet, so I'd like to learn a little more about how the machine works so I can figure out what's going on

- If I understand correctly, the Micro Complex module moves the OS to memory location 0F000H. But I can't find out which memory location the OS is normally in. How can I know if the normal mode or the new memory location mode is activated?

- The module has a switch, which apparently allows you to switch from one rom to another, and/or from one memory address (original or moved) to another. If I understand correctly, there are two copies of the same OS in each EPROM by default, and all you do is change the memory address with the switch. Is this correct?

- Apparently, there's also a Microcomplex floppy control in the machine, and a ram card. So I think it's been modified to run software from the floppy. Unfortunately, there's no floppy drive. I was thinking of loading software via the cassette adapter at first, but I read that the Micro complexe personality module no longer had the commands for the cassette. This leaves the option of loading software via the serial port from a computer, but my question is: with the changes made to the memory addresses and this Micro complex module, is this still possible?

Thanks for your help.

 

[ajacocks]

Welcome to the forum @guibrush !

- Alex

 

[guibrush]

thanks!

 

[Hugo Holden]

Have a look at post #1 on this old thread where I posted the SOL's memory map, running CP/M 2.2 and MBASIC:

https://forum.vcfed.org/index.php?threads/sol-20-memory-management-dilemma.78901/

Another project I made also makes use of spare memory space at D000h to DFFFh to put some ROMs:

https://www.worldphaco.com/uploads/THE_SOL_WITH_THREE_BRAINS.pdf

 

[guibrush]

thanks a lot!

 

[guibrush]

I received my SOL-20 yesterday. It is indeed equipped with a Micro-Complex personnality card. There's also an expansion card attached directly to the motherboard, the Micro Complex Dual 80/64 card, which apparently allows 80-column video mode and continuous use of the 64k ram. There's also a 64k Expandoram RAM card and a Micro Complex Phase Lock II floppy controller card (apparently, the previous owner was a Micro Complex fan). The machine works! I have a prompt in both personality module modes (basic video and 80-column mode). The keyboard doesn't work (normal, because of the foam pads), nor does the ON/OFF button or the fan. I ordered a SUN Type 4 keyboard to take its pads.

So I'm pretty lucky with this machine - I didn't expect so much! Now all I have to do, once the keyboard is fixed, is try to run software on it, and possibly use a floppy drive.

Questions :

- Do you know if there's an S-100 card with an SD or CF card that would allow me to run software on the SOL-20?

- Floppy disk drives are apparently hard sectored. Has anyone ever successfully used a Gotek on a Sol-20?

Here are a few photos

 

[Hugo Holden]

I use soft sector disks, possible with Mike Douglas's virtual sector generator (VSG). I use the Northstar Double density controller card. No support software is required it is all in the ROM's on the card, just type EX E800 and you can run the drives. With a CP/M 2.2 disk in the drives, all works fine.

I put two drive units into an enclosure with Mike's VSG, here is the article describing it.

https://www.worldphaco.com/uploads/EXTERNAL_DUAL_5.pdf

Once I got that running I was able to also use the assembler and make some fun programs, like Steve, my "Walking Man" I got the idea when I saw one on a display at a pedestrian crossing:

One thing about the SOL, it is super easy to get programs in and out of it, on its serial port, especially .ENT files. It is fun watching the files transfer like some ghost is high speed typing the bytes.

 

[guibrush]

Hi thanks for the tip! Yes, I’m planning to feed softwares in .ENT format via the serial port, I already borrowed some on the web. That’s a good hint! I just have to repair the keyboard first to be able to type the commands.

About the floppy: this looks doable. Your mod is awesome!

I have the VSG hard sector simulator, this is a good idea. I’m using it now in another computer ( a Swiss Smaky 6) But I can borrow it. Can you tell me what kind of floppy drive will work on the SOL? I see different format when I‘m browsing .Img files on the web, and I don’t know which one is the good one.

It is possible to create the floppy via the SOL and the serial port? If not, is there a possibility to create them with another methode?

Many thanks for your help?

 

[Hugo Holden]

On the topic of the floppy, Mike Douglas is the expert on that and he helped me.

On the keyboard, I made a tester for it and wrote an article with a lot of detail on how the interesting keyboard works:

https://www.worldphaco.com/uploads/HARDWARE_DIAGNOSTIC_TOOL_FOR_THE_SOL.pdf

 

[Hugo Holden]

Also, if you decide to get interested in the SOL's Tape interface, it is a very clever and interesting system, here is an article I wrote on it:

https://www.worldphaco.com/uploads/The_SOL-20_tape.pdf

I think the SOL-20 is the most interesting S-100 computer of all, because of all of its unique features, its top keyboard and tape interface and the SOLOS monitor that make is quite unique and user friendly system.

 

[Hugo Holden]

PS: as you can see from the article, I used YD-580 disk drives, the reason was they were new old stock and setting the system up, for the first time, I wanted to remove variables like faulty used drives.

I bought a few of these drives on ebay and made duplicate units and two controller cards for comparison purposes.

Once a setup is working, if it fails, its generally easy to find out why, where the fault is, controller card, drive etc, if the system never worked in the first place there could be multiple problems in different places at once.

Having said that out of the unused drive units I bought one had a faulty IC in it from new with a really oddball fault, it worked on its own but inhibited any other drive it was paired with.

I found out later that the chip sets in these particular YD drives won't let them play a hard sector disk.

 

[guibrush]

thank you very much for all this information. Your article on the floppy is very well done and gives me the mechanical information to try to do the same thing. Thanks a lot for the floppy drive model

Could you tell me the format/capacity of the floppies you're using on it, so I know which images are the right ones, or possibly point me to the right image files online? I have a friend who can write me soft sectored diskettes, but I'll need to know what the right disk images are.

Your article on the keyboard is very interesting too, it explains why the pads I bought from an Italian seller only work partially in the SOL-20 keyboard (in fact, some pads work on the same track, others don't, which shows that they're on the edge). These are the ones: https://www.ebay.com/itm/275298265301


I found another source of pads

105 "Foam and Foil" Capacitive Pads for KeyTronic & BTC Keyboard Repair - TexElec

This set of 105 count foam capacitive pads for repairing vintage KeyTronic and BTC keyboards with deteriorating foam pads. These are homemade in house and the 105 should cover what you need with a few extras for your convenience. These will work on keyboards for many different kinds of vintage...

texelec.com

they claim that the latest version of their pads work well on the SOL-20 keyboard, I'll give it a try.

Regarding your article on the cassette interface, it's also very interesting. My main problem is that, as I have the Micro Complex personnality module, the cassette routines are no longer there, so I can't use the cassette interface.

 

[Hugo Holden]

I'd have to check the floppies when I get home.

You could always just use the standard Solos personality module. I seem to warm to original standard systems as they are often better documented and less buggy than "souped up" versions from smaller vendors and there can be a price to pay, for example no tape interface.

I made replicas of the modules I liked using MM5204 UVeproms, which was possible because Martin Eberhard made an ME5204 ROM programmer. But I used my two spare modules up on the Three Brains project. Still, they come up on ebay from time to time.

The SOL-20 keyboard is very fussy about the nature of the pads. As noted the pads which appear to give a universally good result are from the Sun-4 keyboard.

 

[guibrush]

I'd have to check the floppies when I get home.

Ok, thanks!

You could always just use the standard Solos personality module. I seem to warm to original standard systems as they are often better documented and less buggy than "souped up" versions from smaller vendors and there can be a price to pay, for example no tape interface.

I made replicas of the modules I liked using MM5204 UVeproms, which was possible because Martin Eberhard made an ME5204 ROM programmer. But I used my two spare modules up on the Three Brains project. Still, they come up on ebay from time to time.

It will be complicated in my case: I don’t have another personality module, and even if I had one, the micro complex board implies some modification on the motherboard (trace cutting and soldering).

 

[guibrush]

Okay, I got most of the keys to work, so I was able to try loading software via the serial port. Transmission works fine, but there's a problem: the "EN" command used to tell the SOL-20 to write each line to the correct memory address... doesn't exist in the Micro Complex Personality Module. In fact, it's not only the K7 commands that are missing from this damned module, the EN and DUMP commands are also absent. I've managed to substitute the new "FM" command found in the Micro Complex Personality Module brochure, but you have to put it before each line (a pain). Then, looking at the Personality Module documentation, I saw that it was possible to put a SOLOS ROM in the place of one of the two ROMs, which would theoretically allow me to recover a "stock" machine. Except that I also have this other Micro Complex 64/80 card, which is attached directly to the motherboard.
Has anyone ever used these Micro Complex cards and could tell me a bit more about them? In any case, I'm going to make a ROM with SOLOS and see what happens.

 

[Hugo Holden]

If that does not work I think I might have a spare personality module that is tested and working. It is a version that has Solos and DPmon (the latter I have not used because Solos is so great) I'm a bit of a spare parts lunatic.I could look in my parts box. I could sell it, possibly, but you would have to PM me to discuss that. One other option, I could manufacture another replica using the MM5204 Uveproms (these are my favorite lovely vintage parts as the orphan nature of them seems so appealing) and I can program them with the Eberhard programmer, no other programmers can do them, but that would take a little time to organize. But, your plan sounds good to make a Solos ROM yourself.

( Just my opinion mind you; if it were my SOL-20 I would get rid of the hardware modifications and convert it to standard. The other thing I would do is clean up the IC pins and remove the oxides from them, check every single IC socket pin for spring tension using a test pin taken from a defunct IC and soldered to a small wire handle. Many Sols used TI brand IC sockets that grab the pin from side to side, on its thin side, rather than the flat, so it is the thin sides of the IC pins that require cleaning. If you look at some you may find a grey or black line on the sides of the IC pins where the dissimilar metals interacted, this needs to be scraped off. The other thing, is that is is worth replacing those pale blue CTS dip switches, at this age many have gone intermittent. I replace these with an IC socket and fit new low profile Omron switches that have a form factor like an IC. Otherwise intermittent faults, related to bad connections, can plaque the computer. If you do have to replace any TI sockets, there is one saving grace, the plastic shroud can be lifted away, and the pins removed one by one, before clearing the holes of solder with the sucker. This is a lot less stressful for the pcb).

 

[guibrush]

Thanks for your proposal for the personality module. Tonight, I'm going visiting a friend who can make me the SOLOS ROM, so I'll be able to test it. I'll keep you posted.

As for bringing the machine back to its original state: that was my very first idea, but the problem is that to install this card, 30 chips had to be removed from the motherboard. And I don't have those chips, of course. So it's quite complicated to do.

for the other work: yes, I think it will be necessary whatever happens.

Thanks!

 

[Hugo Holden]

I see from the photo that another card was added with lots of chips on it. At least the chips in the SOL are easy to get and not expensive.

 

[guibrush]

Yes, the installation of the Micro Complex 80/64 card requires to remove 30 chips from the motherboard, as this board piggy back there. The only documentation I found about this card is there:

https://deramp.com/downloads/mfe_archive/070-Books%20Newsletters%20and%20Magazines/Solus-Proteus/Proteus%20Vol04-04&06.pdf

Yesterday, I went to my friend with my SOL and he burned me s SOLOS rom: the rom seems to boot correctly. I have a prompt, and I can use the EN and DUMP command! We changed the caps on the 64k memory expansion, tested all ICs and found that a 7425n chip is defective. Despite this chip being defective, I can obtain a positive memory test (under DPMON) on the two central memory bank, between 4000 and BFFF. The first bank (0000 3FFF) and the last bank (C000 FFFF) report errors. Removing the chip give errors on all banks. So, it's definitively related. Because the first bank from 0000 isn't working, loading .ent files fail. I'm looking now for this chip and hope that with a new one the whole memory board will work. On the pic you can see that I entered values in 0000 and that reading it back give another values, and on the other hand making the same on 4000 give back the correct values. There is a pic with the good memory test result too. This is where I am now. SOLOS boot, but for me it's still unclear if the .ent files can be executed correctly.

Small question: does the programs in .ent format have to access the video ram or the rom directly? I'm asking this, because I'm failing to understand how SOLOS can display something when the memory RAM is hidden by the Micro Complex board.

 

[wperko]

Hi,

That Micro Complex notice might explain the odd modifications that were done to my Sol-20 rev. D board which is going under repair. There was no Micro Complex adapter board and there are the proper Sol-20 chips in almost all the sockets (I had to replace one chip as it was not correct), but I'm hoping my board can be brought back to life without too much expense.


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