Oric Nova 64 display issue.

If you want to ask questions about how the machine works, peculiar details, the differences between models, here it is !
How to program the oric hardware (VIA, FDC, ...) is also welcome.
User avatar
Dbug
Site Admin
Posts: 4444
Joined: Fri Jan 06, 2006 10:00 pm
Location: Oslo, Norway
Contact:

Oric Nova 64 display issue.

Post by Dbug »

Since I spent the week-end with my soldering iron, I decided to take a look at the Oric Nova 64 which had a display problem.

I made a 10 minute video about it, including the use of a thermal camera and diagnostic cartridge.

My biggest question is: How are these two memory chips (TMS4464) used, do they each handle a nibble of each byte, or is one responsible for the bottom 32K and the other for the top 32K?

Anyway, here is the video, and all feedback is welcome!

User avatar
kenneth
Squad Leader
Posts: 515
Joined: Fri Nov 26, 2010 9:11 pm
Location: France PdD
Contact:

Re: Oric Nova 64 display issue.

Post by kenneth »

The memory chips are using 64k bits x 4 bits each. maybe you can fill the screen with the "50Hz value" ? If the memory chip is failed, you can exchange them, the "60Hz value" on the screen will disappear. Did you tried the RF antenna mode?
User avatar
Dbug
Site Admin
Posts: 4444
Joined: Fri Jan 06, 2006 10:00 pm
Location: Oslo, Norway
Contact:

Re: Oric Nova 64 display issue.

Post by Dbug »

I've not tried the RF, but I guess I can, does not hurt :)

So I've digged a bit more, and the motherboard is 100% identical to the 16K Oric 1 (with some white smudge to cover the 16K markings) where they replaced the TMS4416 by TMS4464.

Regarding the 64kbits*4bit each, does that mean that both chips are selected at the same time, one providing the bottom 4bit and the other the top 4bit?
User avatar
Dbug
Site Admin
Posts: 4444
Joined: Fri Jan 06, 2006 10:00 pm
Location: Oslo, Norway
Contact:

Re: Oric Nova 64 display issue.

Post by Dbug »

By the way, I'm documenting my findings on Twitter:


Since both "Buggy Boy" and "Pushing the Enveloppe" demos are both running fine (they use pretty much all of the memory, including the overlay), I'm feeling confident that the RAM and Multiplexers are just fine, else that would crash.

Looking like it's actually a problem inside the ULA.
User avatar
iss
Wing Commander
Posts: 1641
Joined: Sat Apr 03, 2010 5:43 pm
Location: Bulgaria
Contact:

Re: Oric Nova 64 display issue.

Post by iss »

My experience and fixing Oric Nova64 :D
In my case there ware garbage instead of characters.
For me this is ULA issue - try to change it with known working one.

About the RAM 4464: yes, its organization is 64k x 4bit. Although it's theoretically possible to be used as "one responsible for the bottom 32K and the other for the top 32K", such approach is too difficult from hardware point of view. So, I'm 100% sure that both chip are addressed together and one supplies low 4 bits and the other the high 4 bits.
User avatar
Silicebit.
Flight Lieutenant
Posts: 313
Joined: Thu Jan 12, 2006 10:18 pm
Location: Madrid, Spain
Contact:

Re: Oric Nova 64 display issue.

Post by Silicebit. »

iss wrote: Mon Jun 06, 2022 8:45 am .... I'm 100% sure that both chip are addressed together and one supplies low 4 bits and the other the high 4 bits.
iss, you’re right. :)
Oric user since 1984. YouTube
User avatar
Dbug
Site Admin
Posts: 4444
Joined: Fri Jan 06, 2006 10:00 pm
Location: Oslo, Norway
Contact:

Re: Oric Nova 64 display issue.

Post by Dbug »

The crazy thing is that I had already tried to swap the ULA, but I had only tried one, so looks like I should have tried with other but at that time I had not yet ordered a bunch of these.

And I tried again with the ones I received from eBay, and it's working!



That's one more Nova 64 in running order, so I guess time to do a part 2 of the video showing details.

I guess it also means I suck at using the diagnostic cartridge, and that the two green leds leans it did not find anything wrong.
User avatar
iss
Wing Commander
Posts: 1641
Joined: Sat Apr 03, 2010 5:43 pm
Location: Bulgaria
Contact:

Re: Oric Nova 64 display issue.

Post by iss »

Cool, one more Oric resurrected!
The key words here are (as you said) "partially damaged" chip - this is not a rare phenomena but difficult to diagnose. 8)
User avatar
kenneth
Squad Leader
Posts: 515
Joined: Fri Nov 26, 2010 9:11 pm
Location: France PdD
Contact:

Re: Oric Nova 64 display issue.

Post by kenneth »

The diagnostic cartidge can detect something wrong when reading the internal architecture by the expansion bus...but the rvb output is not reachable by the tool, this is the only failure undetectable.
User avatar
Dbug
Site Admin
Posts: 4444
Joined: Fri Jan 06, 2006 10:00 pm
Location: Oslo, Norway
Contact:

Re: Oric Nova 64 display issue.

Post by Dbug »

kenneth wrote: Mon Jun 06, 2022 10:03 am The diagnostic cartidge can detect something wrong when reading the internal architecture by the expansion bus...but the rvb output is not reachable by the tool, this is the only failure undetectable.
The main issue here is that the documentation is not clear at all.

I did not realize that the led was not showing an error code at all, but that instead it was just stopped on this test and waited for me to press the NMI button.

When the screen display works, it's super simple to use, but without display, not obvious at all, even with the printed out manual on my side.
User avatar
Chema
Game master
Posts: 3014
Joined: Tue Jan 17, 2006 10:55 am
Location: Gijón, SPAIN
Contact:

Re: Oric Nova 64 display issue.

Post by Chema »

Great! Another Nova running fine. Congratulations!
User avatar
Dbug
Site Admin
Posts: 4444
Joined: Fri Jan 06, 2006 10:00 pm
Location: Oslo, Norway
Contact:

Re: Oric Nova 64 display issue.

Post by Dbug »

Final video with also an demonstration of how the Diagnostic Cartridge actually works on a fully working machine.
User avatar
kenneth
Squad Leader
Posts: 515
Joined: Fri Nov 26, 2010 9:11 pm
Location: France PdD
Contact:

Re: Oric Nova 64 display issue.

Post by kenneth »

Well explained! I also use the large screwdriver for this. :mrgreen: Finally you need the screen for a complete diagnosis 8)
Хвала што сте поправили "NOVA" :wink:
User avatar
Dbug
Site Admin
Posts: 4444
Joined: Fri Jan 06, 2006 10:00 pm
Location: Oslo, Norway
Contact:

Re: Oric Nova 64 display issue.

Post by Dbug »

kenneth wrote: Mon Jun 06, 2022 7:37 pm Well explained! I also use the large screwdriver for this. :mrgreen: Finally you need the screen for a complete diagnosis 8)
Хвала што сте поправили "NOVA" :wink:
Нема на чему
User avatar
Silicebit.
Flight Lieutenant
Posts: 313
Joined: Thu Jan 12, 2006 10:18 pm
Location: Madrid, Spain
Contact:

Re: Oric Nova 64 display issue.

Post by Silicebit. »

Great, another Oric coming back to life! Congratulations Mike!
kenneth wrote: Mon Jun 06, 2022 7:37 pm ... I also use the large screwdriver for this. :mrgreen: ...
The large screwdriver is a powerful tool to remove chips, I use it too. :D
Oric user since 1984. YouTube
Post Reply