ITT2020

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ITT2020

I am hoping someone can advice me. I have two questions.

I have an ITT2020 which is a 1979 Apple II clone. I am about to attempt to get this one in to fully working order. I have two question which I am hoping you guys may be able to help with.

1) my computer came with a disk drive but no controller card. I have been reading this little line "ITT also supplied a floppy disk drive that was identical to the Apple II disk drive with 13 sectors and DOS 3.2. They never supplied the upgrade to 16 sectors and DOS." here . . http://www.computinghistory.org.uk/det/31495/ITT-2020-Computer-Apple-II-Clone/.

I am trying to workout if this means I can get a standard Apple II disc controller card or do I need a specific one. Any ideas gratefully received.

 

Additionally when the machine boots I see gibberish, i get a beep and then a cursor. I can use CTRL + B then RETURN to get to a basic prompt. Is that normal or should it boot to something else?

 

 

Any help appriciated.

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Photos

Someone posted this link a while ago, which also has high resolution photos of the ITT's original disk controller:

http://quartdepomme.fr/quartdepomme/Hardware_Apple_II_Clones/Pages/ITT_2020.html#16

http://quartdepomme.fr/quartdepomme/Hardware_Apple_II_Clones/Pages/ITT_2020.html#17

It certainly looks extremely similar - same components. If you were unsure, you could even compare whether the pinout of the connectors matches the original...

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I guess I am 99% sure the pin

I guess I am 99% sure the pin out will be the same. It's this comment about "ITT also supplied a floppy disk drive that was identical to the Apple II disk drive with 13 sectors and DOS 3.2. They never supplied the upgrade to 16 sectors and DOS." .  . I presume that upgrade came in the form of a rom. However I am unclear if this was to the main mother board rom, the controller card rom or rom inside the disc drive.

This link mentions it a bit but I am just not 100% clear on what it means for my set up. . .http://fileformats.archiveteam.org/wiki/Apple_II_16_sector_disk

 

 

 

 

 

 

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Controller ROMs

There are no ROMs within the disk drive. The disk drive is "stupid" and simply inputs and outputs the current "magnetic state" of the read/write head to the controller card. There is a simple state machine controlled by a logic PROM (the P6A) on the controller card, which converts the input/output signal from the disk drive to a byte. Everything else is done by software - motor controls, even the precise timing for the read/write heads.

That was the magic Woz way of doing things: simple and cheap - but still smart and fast. Compare this to the complicated design of other computers - like the C64's disk drive, which even had its own 6502 processor to control the drive - and was still slower...

The P6A PROM on the controller card differs between the 13/16 sector mode - that's the little device controlling the bit encoding. Also the little 256 byte (firmware) ROM on the controller card differs. The rest is all done by software (DOS).

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Haha, yep I was one of those

Haha, yep I was one of those suckers who paid more for a Commodore 1541 than I paid for my c64 only to discover it was barely faster than tape :)

 

Ok so it seems logical that if I buy any Dsik II controller card it will work, and my drive should be dumb and just do what it is told. I now await the postal service :).

 

I had another quation is my original message realating to the gibberish at boot up. Is that normal in an earlier Apple II / clone?

 

Joe

 

 

 

 

 

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You can use a standard Disk ]

You can use a standard Disk ][ controller in the ITT 2020. One issue that you will face is tha it will not run all Apple ][ software. The Integer BASIC in the ITT 2020 was itself custom, an not entirely compatible. The ITT had a uniue software catalogue that can only run on the ITT, so you hae a few programmes that are speciically designed for it, but quite a lot of software may not work properly, or may not work at all, that was releaed after the Europlus. 

 

Other than that, the ITT is a phenominally good system. 

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Probably not
arkleyjoe wrote:

I had another quation is my original message realating to the gibberish at boot up. Is that normal in an earlier Apple II / clone?

The thumbnail images are really tiny and hard to see, and I don't know the ITT, but it doesn't look normal. The Apple would just print its "Apple ][" boot message and enter a basic prompt. The clones often changed the "Apple ][" boot message to their own name. But why should a clone, especially one which was obviously designed to make hardware improvements, intentionally output gibberish?

Do you have any cards installed in any of the slots?

The Apple ROM checks each slot and if it finds a slot with a boot ROM, it just executes its code. The disk controller card contains a boot ROM (that's the little 256 byte firmware ROM). So once installed, an Apple no longer boots to basic prompt, but whacks the disk's head against the mechanical stop (the famous "brrrrrrrt!") and then starts loading the disk. You could press "Control-RESET" to keep the Apple from executing the slot boot ROMs, so it would again boot to basic prompt.

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Ok thanks for all of the help

Ok thanks for all of the help so far guys.

I did not realise those thumbs were so tiny. Here is the full size image of what I get at boot. As I mentioned I can get a basic prompt with CTRL B + ENTER

Re: "But why should a clone, especially one which was obviously designed to make hardware improvements, intentionally output gibberish?"

In this post >https://www.applefritter.com/content/gibberish-video-upon-bootup-early-series-apple-ii

It mentoned early systems booted to gibberish, although maybe I am taking it too litterally?

Assuming this is a error  . .  do you have any pointers as to where I may start looking (maybe RAM or ROM fault?) or is it a case of just working though everything?

 

 

 

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Ahh and I missed your

Ahh and I missed your question "Do you have any cards installed in any of the slots?" no none at all currently.

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Anything really...

No cards, ok, so it cannot be an issue with any boot ROM in any of the slots...

I'm not aware of the rev 0 mainboard gibberish issue. But the other post says that there was "no beep". That suggests the rev 0 mainboards sometimes did not do a proper reset at power-up. You said you do get a beep though - so yours is cleary running its boot sequence.

But it's impossible to guess what would cause this at this point. If this was an error at all, it could be anything really. RAM/ROM - or any other interfering logic chip... See if you can find any system diagnostics software for the ITT - to test ROM/RAM. Or maybe it has a way to trigger a self-test (like the Apple's Both-Apple-keys-Control-Reset diagnostics).

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I'll go out on a limb here...

I'm relatively new to the Apple II scene, but I have seen similar on my Europlus. 

My order of attack would be:

  1. check for discoloured / corroded pins on any chips. My europlus had a HEAP of components where the legs were an interesting tarry black. I carefully cleaned them in an ESD area with an ink eraser. (the 6502 looked hideous, in particular)
  2. Depending on how much RAM you have, remove half, then swap the halves. Easy on an Apple (and my clones) as everything is socketed. There's a little MC "memory test" you can enter in this thread that I used to help me diagnose my Apple II - https://www.applefritter.com/content/testing-ram-apple-ii-plus

Good luck!

 

Chesh

 

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I immediately suspect faulty

I immediately suspect faulty RAM here. I haven;t touched an ITT 2020 for over 25 years, so, this is had to diagnose. I hae run into similar issued with defective language/RAM cads and Videx cards, but not bare board. I agree though: Check for oxidation on components. 

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