ITT2020

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...

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).

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. 

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.

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).

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

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. 

I have a functional ITT 2020 with EPROMS on board, when it's booted  up it shows APPLE II at the top of the screen. Then you press ctrl+ reset you get Applesoft prompt "]" I hope it helps.

Regards.

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?

This is the normal behaviour for the old F8 ROM. Before the later Autostart ROM, booting the Apple will drop you into the monitor (the * prompt). Pressing CTRL+B (BASIC) will let you enter into BASIC.

If you add a Disk II controller, the old F8 ROM won't boot it automatically. You either have to type 6 CTRL+P and Enter from the monitor or PR#6 and Enter from the BASIC prompt. Hence the Autostart name :-)

amauget wrote:

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?

 

This is the normal behaviour for the old F8 ROM. Before the later Autostart ROM, booting the Apple will drop you into the monitor (the * prompt). Pressing CTRL

True, but IDR a huge block of ? symbols before the prompt. Was that normal, too?

Timelord wrote:

 

True, but IDR a huge block of ? symbols before the prompt. Was that normal, too?

Absolutely. The Apple displays what is in memory at boot. Since the RAM isn't initialized...

Excerpt from The Red Book :

"Now turn on the power switch on the back of the Apple. The indicatorlight (it's not a switch) on the keyboard should now be ON. Ifnot, check A.C. connections. Press and release the "Reset" buttonon the keyboard. The following should happen: the Apple's internalspeaker should beep, an asterisk ("*") prompt character should appearat the lower left hand corner of your TV, and a flashing white squareshould appear just to the right of the asterisk. The rest of theTV screen will be made up of radom text characters (typically question marks)."

The original ITT 2020 had no AutoStart ROMs, so if you turn it on you see the screen full of signs and in the last line you see the asterix and a cursor. This is normal behaviour. You can of course replace the F8 ROM with an AutoStart ROM from an Apple ][ Plus but then it is not longer original. The ITT 2020 had a modified AppleSoft called PalSoft in the D000-F7FF ROMs. The main difference in hardware was the high horizontal resolution of 360 pixels instead of 280 in the Apple ][.