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Digital Group Z80 to 8080 Fun

Hi All;

Glitch, Yes, DG used a Software approach to for the Timing of the One's and Zero's, and thereby they could read 'basically' anything from 300 Baud to 1300 Baud, depending on some of the filtering and the Loop timing in Software..
I can't find it, it's buried somewhere but, there are three articles written by Dr. Suding in Byte Magazine on His Z-80 Card, and the TV Output and the Cassette Interface, which Explains each in Greater Detail, and there is also an Article and Listing on the Educator Program as well..
I found/have these in the Best of Byte book..

I think the Easiest for me is to put an blank board in the Altair and another one in the Digital Group Processor Slot and try to make the S-100 signals look like the signals needed for what the Digital Group Processor Board would deliver to the Digital Group MotherBoard..
Also, in the Altair I have a full 64K of Memory and a Simple Editor for Depositing and Examining memory, that I don't have in the Dg Machine..

THANK YOU Marty
 
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Thanks Marty. Yeah.. it definitely seems to be related. It has the same mounting feet as mine, same bezel, same placement of parts, etcetera. Definitely some things are different -- it has an extra head? But yeah.. hmm.

I'm likely to fail regardless of going double or quad on the Phidecks. Quad just seems cooler for some reason. Mind you, I'd still be missing the lids. Probably won't ever find those. Have to think about it.

Marty said:
Hi All;

Falter, No and Yes.. So, One Motor has Triple I marker on it, which is the Parent Company for Phi-Deck..
I can't tell for sure, but, it either is a ReBranded PhiDeck or a Knock-off copy of a PhiDeck..
So, If You thought it would be worth the price, You could/might be able to use it for Parts for what You already have..
If I were You, I would just stick with having the two drives and the Enclosure, and work on getting those two units working, before wanting to make it into a four hole drive System, which would be just as un-usable if You cant get a two hole system working..
But, for looks if You really want a four hole drive system, then it would probable be OK..
The Motors are 5 Volt, but, I can't say what speed the drive is set up for..

Brad, If You decide to get it, and He Doesn't want to Send it to You up their in Canada, Just Give Him My Address and I will ReSend it to You..

THANK YOU Marty
Click to expand...
 
Hi All;

Brad, "" How many Phidecks do you have? ""
I forgot at present, and I can't get to anything at present, but I think three or four..
But, Remember, as stated before, these are for my Meca Alpha System, and they run at a different speed and Use different Circuitry.. And are at a different voltage as well, motor wise..

I have wired up the Altair side of the Extended/cable card..

THANK YOU Marty
 
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Hey Marty -- are you fairly confident that the garbage characters after the 'Read Initialize 8080 Cassette' message are in fact to be expected, ie. as a consequence of the video being 64char rather than the 32 this card was set up for?

I'm just concerned that the board isn't, in fact, working correctly, but I don't know what to expect. With the Z80 board, if you put a tape in and play it at the prompt, doesn't matter what machine it's for it'll always produce a reaction on the screen. The 8080 board doesn't do that. In fact, the only time I get it to punch out anything at all is if I (sometimes) remove the Ear connector on the tape deck and then (without stopping the tape) jam it back in. If I just play a tape the usual way and let it go, it'll never put up the 1s 2s, etc.

I would have thought if it was simply 32 bit being expanded out to 64 bit you'd have the initialize message midscreen but then blank again after..
 
Hi All;

Brad, If I remember correctly that was correct..
But, if or since You can get the Z-80 Board to work correctly, then, I am fairly confident that the Video part is working correctly..
So, for Now I would say the Video Board is OK, and the same reasoning for the Cassette Reading, that You can read a tape for the Z-80 Board and it is OK, as well..
So, the I/O Board I am sure is fine as well..
Now, that leaves the 8080 Board, that needs to be checked and IF you have the Capability, to make a single change to the Eprom, You can then use the new Epron in either a 64 or a 32 character Board..
You need to make a copy of Your Eprom and change Address Location '000 '352 (Octal) from a '002 to a 004, (Octal), this will fix Your problem of misc characters..
I think if You look at the Z-80 code in that same area, You will find a '004 instead of an '002 and that was the fix for the Z-80 Eprom as well, so it would work in either a 32 or a 64 character setting.. I Don't have a copy of the Z-80 Eprom code in front of me to know for sure..
Then One at a time Change out each IC that is in the 8080 board and after that change it back if it is good with the same kind from the Z-80 Board, Check to see that the Z-80 Board is fully functional, and will Load a program.. Doing this to check each IC in the 8080 CPU Board, Replacing any bad IC's and Rechecking what You have replaced and re-checking in the Z-80 Board as well..
I know HOW long this takes, I have done it myself, when trying to find a problem on a Board, but I did Z-80 to Z-80 and so forth..
(Also, the Reading circuitry of the Cassette Board MIGHT need some tweaking..)
After checking what You can with the Z-80 CPU Board, and with hopefully a re-programmed Eprom, Hopefully the 8080 board will work slightly better, after that You would need to switch out the other parts on the 8080 Board with other Parts that You might have around..
I cannot say that the 8080 board is/was fully functional, I know the one I have left is Not Functional, but I have not at present determined why, as I have no other boards to trade and try IC's with, and the only working Board that I have at present is the i/o Board, both my 8080 CPU and my 32 and 64 character boards and Cassette interfaces do not work at present..

Also, If You can reply and or ask a question more often in a day, I can respond quicker than You seemingly once a day reply.. Just a suggestion..

THANK YOU Marty
 
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Thanks Marty.. I have been slowly doing that. I've noticed some chips removed have no noticeable effect on the board's ability to 'post' the init message. I wish there was better documentation on the 8080 board available.. like the z80. But all I've seen are drawings.

I am assuming of course that the wiring of the motherboard wouldn't have an impact? Ie.. would not be different for a 8080 vs z80, since DG advertised the ability to simply swap cpu boards and nothing else as an advantage?
 
Hi All;

Brad, "" I am assuming of course that the wiring of the motherboard wouldn't have an impact? Ie.. would not be different for a 8080 vs z80, since DG advertised the ability to simply swap cpu boards and nothing else as an advantage? ""
Yes, between those two, their are no differences..

"" I wish there was better documentation on the 8080 board available.. like the z80. But all I've seen are drawings. ""

Make sure You have checked all of Bryan's documentation on the 8080 along with what You have from Bitsavers..

Their is the 8080 Op Sys file which is a PDF, I am not sure which place I got it from, so check both places..
I found it in Bryans place, here is the link to the page I got it from..

http://www.bytecollector.com/dg_docs.htm



I also found when just looking at my usual sites that I Browse thru. A thing came up on how to copy cassettes to my computer, and it recommended a program called Audacity which I downloaded, So now if or when I can find my lost tapes, I can copy the tapes to my computer and download them to You Brad and everyone else..
No, one told me about this program, nor how to do it..

THANK YOU Marty
 
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Okay so.. on the 8080 front.. I discovered something. Because fooling with the crystal seemed to get it going I decided to pull the crystal to see what happens. On the z80 if there's no crystal you get a screen full of random junk. But on the 8080.. I get exactly the same Initialize screen! So maybe the board isn't really running? Not sure how it even gets a msg up on screen.. but yeah.. crystal is having no effect.

New problem.. in trying to load MaxiBasic and other software with the z80.. I am now getting ....'s when the first row of 0s appears during the load process. It starts off normal and goes one round of 1 through 7s before that happens. I'm not exactly 100% on what the numbers represent.. Marty you said 0-3 = 1 k, 4-7 = the next 1k, then 0-3 again is the third k? Did I read that right? Based on that I went thru row 3 (er.. I guess that would be row 2 since it starts at 0.. in other words third row up fr bottom on right hand side) of the first memory card with known good but no change.. so I'm thinking I read that wrong.
 
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Hi All;

Brad, But on the 8080.. I get exactly the same Initialize screen! So maybe the board isn't really running? Not sure how it even gets a msg up on screen.. but yeah.. crystal is having no effect. ""
I don't Understand That at all ??? So, I would guess that somehow a Crystal type of signal is getting thru to the 8080..
Also, remember that the Crystal in the 8080 is 18.00 Mhz which is divided by about 9 and is converted to a two phase clock signal..
"" Not sure how it even gets a msg up on screen.. " Somehow it's being written to the 2102's in the Cassette/64 Character card..
Possibly the Eprom is constantly being Written / Addressed by the counting circuitry in the TVT circuitry, the inputs and outputs from the 1702 Eprom are constantly, being turned on and off and so are NOT controlled by the 8080..

"" New problem.. in trying to load MaxiBasic and other software with the z80.. I am now getting ....'s when the first row of 0s appears during the load process. It starts off normal and goes one round of 1 through 7s before that happens. I'm not exactly 100% on what the numbers represent.. Marty you said 0-3 = 1 k, 4-7 = the next 1k, then 0-3 again is the third k? Did I read that right? Based on that I went thru row 3 (er.. I guess that would be row 2 since it starts at 0.. in other words third row up fr bottom on right hand side) of the first memory card with known good but no change.. so I'm thinking I read that wrong. ""
"" Marty you said 0-3 = 1 k, 4-7 = the next 1k, then 0-3 again is the third k? Did I read that right? ""
YES !!!
My guess is that You need to Re-Seat Your Memory, And OR Check all of Your Memory..
The Other Possibility, that I mentioned Before, is that Your Cassette Reading Circuitry needs Tweaking !!!!!
Read the Manual for the TVT-64 for Setting up the OP Amps to correctly Read Your Cassettes !!!!

THANK YOU Marty
 
We'll have to put this one down to 'operator error'. I noticed even if I let it keep going after the bad '0s' it would be fine until it hit 0 again. I then realized one of the 7404 sockets on the board were empty. This was due to my troubleshooting with the 8080 board. Soon as I put that in, everything's working fine again on the Z80 side.

And the 8080 is progressing a bit. I tapped the crystal a couple times on my workbench and now, amazingly, it consistently produces activity when I run the tape. Wish I had an 8080 tape to work with.. that would tell me if those random characters after the init message are a symptom of something serious.
 
Hi All;

Brad, Congratulations on getting things to work !!!
I hope in the sometime future to get You a Digital copy from Audacity and once I FIND my tapes..
I still think Glitch has a copy of ICOSE which is an 8080 tape.. And Maybe He could make a Digital Copy of it for You..
"" that would tell me if those random characters after the init message are a symptom of something serious. ""
Not Necessarily, as stated in a posting above.. You need to have an 1702 Reprogrammed with the value, that I told You about above..
Then, If there are still random characters, after changing to the Fixed Eprom, then I would say 'You have a problem' ..

THANK YOU Marty
 
Hi All;

I Found the Cassettes, and much to my shagrin, I have both of my 8080 Tapes, a well as some of the other ICOSE Tapes..
Now, I have to find the correct cables..

THANK YOU Marty
 
Hi All;

Hopefully, I can copy the .wav file for download and Someone can try it, and tell me IF it is OK..

No, I Don't know How to save a .wav file to here.. Maybe someone can let me know if it is possible and How to do it..

THANK YOU Marty
 
You could just email it to me Marty and then I can find a place to post it. Or just reemail it to other DG users. My email can handle up to 50mb attachments.
 
Hi Brad;

It's not Your End, it's my end..
The file is about 31mb and my email will Only do files smaller than 10kb..
I already tried to send You the file, and I found out it was about 30 times toooo big to send to You..

THANK YOU Marty
 
Hi All;

Glitch, Please Email me and tell me what and how to do this..

But, remember, that this is a trial Run, and it may not work, or it could be a corrupted file..

THANK YOU Marty
 
Email sent! No worries about it maybe being a dud, I own the server and it doesn't cost me anything to move a few files around.
 
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