New Oric Project. The OriClone-1

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.
DigitalDunc
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New Oric Project. The OriClone-1

Post by DigitalDunc »

Hello forum!

Firstly, I'm newly joined up here and haven't messaged before so I apologise in advance for any fluff-ups I may make. Now, I've been playing around with Oric's since I was a nipper just last week decided to make myself a new one based roughly on Manoel Trapier's excellent schematic. I'm in the process of schematic capture using EAGLE (Should have used KiCAD but hey ho) and have gotten as far as the video portion. Next up is the CPU and 6522 portion. I'm not going with the W65C02TPG-14's I have lying around in this case as some people have used illegal opcodes in their code but can anybody see a reason why I shouldn't use the WDC version of the 6522? I'm aware they've beefed up the output buffers somewhat since the old originals came out.

Also, why did they go with a 7905!!?

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Re: New Oric Project. The OriClone-1

Post by Dbug »

Welcome,
I'm not an hardware specialist, so I'll let the other answer you, good luck :)

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Re: New Oric Project. The OriClone-1

Post by mikeb »

DigitalDunc wrote:
Sun Jan 05, 2020 3:32 pm
Also, why did they go with a 7905!!?
The 7905 has a lower overhead (difference between the input and output voltage), which means it can still deliver 5v at a lower input than a 7805 would.

So they stuck it in the ground leg, and regulated that instead of the +5v rail.

The only time this causes a problem is when either someone replaces the regulator and pays no attention, "assuming" that 7905 must be a typo/equivalent to 7805wrongly fitted part.

Or, when someone powers an Oric from a non-floating PSU (e.g. a bench supply, ex PC power supply), that has *its* ground referenced to mains earth/other equipment that is earthed, and then plugs something grounded/earthed into the printer, cassette, expansion, video or UHF port.

Bypassing the regulator, and providing approx 9v to all the TTL bits.

If you're feeling adventurous, and wish to drag Oric into the 21st Century, you could provide a "Universal" voltage input: A bridge rectifier (now you can use AC, DC, any polarity, who cares?) followed by a "5-24v input, 5V output Dc-DC Buck converter" (plenty of small modules on eBay), and then all this will go away.

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Re: New Oric Project. The OriClone-1

Post by DigitalDunc »

Well, certainly I think switch mode is the way to go given how, um, warm the standard 7905 runs. Good call that! I was leaving the PSU section to nearer completion as I've been considering adding a few other goodies meaning I don't quite know what I'm going to want. A joystick port or two seems an attractive addition also.

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Re: New Oric Project. The OriClone-1

Post by DigitalDunc »

I've made some progress, but of course, there are probably many faults in it. Anyway, I thought I'd share my progress with the community and ask that if you think I've made a mistake so far that you give me a heads-up! I have been giving some thought to the signal names and how the Oric busses particular operation differs from that of other 6502 systems I've worked on but this is my first Oric hardware project.
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OriClone-1 EAGLE project.zip
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DigitalDunc
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Re: New Oric Project. The OriClone-1

Post by DigitalDunc »

Whilst I haven't seen anybody reply, I did find some issues and further the schematic. I've made the updates available. Another couple of weeks and I might even have a working board. Did I just jinx myself?
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OriClone-1 EAGLE project.zip
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Chema
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Re: New Oric Project. The OriClone-1

Post by Chema »

A quick post to state I am following your project. I find it really interesting and I am impressed by the talent you hardware people are showing lately with your projects.

Unfortunately, my knowledge about hardware is nearly zero, so I won't be able to help at all... :(

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Dbug
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Re: New Oric Project. The OriClone-1

Post by Dbug »

Regarding feedback, things here seems to obey no clear logic: Sometimes there are no messages for a number of days, and then (like yesterday) there's an avalanche of answers all over the place :)

Now, specifically regarding your project, it's generally easier to attract people by having pictures, because only a limited number of people happen to use model software (like Eagle or other).

The tendency is also to have some online repository with the updates there, and link to it - because at some point you will hit the forum limitations on file size -

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Re: New Oric Project. The OriClone-1

Post by DigitalDunc »

Well! You’re right of course, and I should really chuck it on github or suchlike. I didn’t give it enough thought on how I might generate engagement to spur the project along and add value to those that might have an interest. Pictures are a great idea.

EDIT:-

I’m going to set up a repo and come back with a link. This way, I won’t need to keep posting updates.

EDIT 2:-

Right, It's committed to github now. :)
https://github.com/DigitalDunc/OriClone-1.git

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Re: New Oric Project. The OriClone-1

Post by Dbug »

Good!

Now, I would recommend that you add some information to the readme, so people who reach the github page knows what the project is, the intended result, current state of the project, known issues and things to implement, etc...

Basically, on all these things you need to give all the overview information, so people ask you important things instead of "what's this project about exactly"?

Since you mentioned the inspiration from Manoel, don't hesitate to also add a section with links to relevant materials, etc...

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Re: New Oric Project. The OriClone-1

Post by Godzil »

DigitalDunc wrote:
Sun Jan 05, 2020 3:32 pm
Hello forum!

Firstly, I'm newly joined up here and haven't messaged before so I apologise in advance for any fluff-ups I may make. Now, I've been playing around with Oric's since I was a nipper just last week decided to make myself a new one based roughly on Manoel Trapier's excellent schematic.
Happy my schematic is helpful, if you find any mistake don't hesitate to report them :)
I'm not going with the W65C02TPG-14's I have lying around in this case as some people have used illegal opcodes in their code but can anybody see a reason why I shouldn't use the WDC version of the 6522? I'm aware they've beefed up the output buffers somewhat since the old originals came out.
If I remember one of the WDC chip have a hardware bug they never fixed, don't remember if it is the VIA or the PIA.

One potential "issue" is WDC chips are CMOS where the original Oric was using NMOS for both the 6502 and 6522 so voltage level are slightly different (and is cause of some of the issue we have with the expansion connector)
mikeb wrote:
Sun Jan 05, 2020 7:03 pm
DigitalDunc wrote:
Sun Jan 05, 2020 3:32 pm
Also, why did they go with a 7905!!?
Or, when someone powers an Oric from a non-floating PSU (e.g. a bench supply, ex PC power supply), that has *its* ground referenced to mains earth/other equipment that is earthed, and then plugs something grounded/earthed into the printer, cassette, expansion, video or UHF port.
Having the negative connected to earth is sadly common, especially with a TV (or monitor), and that's where the Oric speciality is annoying.

9V power supply tend to be isolated, but not most electrical equipment. It would work as long as the Oric power supply is an isolated one, but you will get some nice tingles when you touch both ground before both devices are connected. It can also cause some nasty issues.

Using the 7905 was a mistake, especially because using a 7805 would have not created any issue.
I really think that the choice of the 7905 was more for $$ than anything else (Like tangerine having ton of them in stock, or them being able to get them for cheaper, regardless to the type of issue it could create, that was a big overlook)
Last edited by Godzil on Thu Nov 05, 2020 12:05 pm, edited 1 time in total.

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Re: New Oric Project. The OriClone-1

Post by xahmol »

Cool! Only notice this one now. Absolutely zero hardware skills myself as well, so really can give no help.

But certainly a very interested potential customer if this project can provide the board for a 100% compatible Oric Atmos clone with the same look and feel if placed in an Atmos case/keyboard and all original connectivity with modern niceties as HDMI output (also for sound) and maybe disk emulation via USB ports, joystick port and network connectivity included......

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Re: New Oric Project. The OriClone-1

Post by mikeb »

Godzil wrote:
Wed Nov 04, 2020 11:36 pm
Using the 7905 was a mistake, especially because using a 7805 would have not created any issue.
I really think that the choice of the 7905 was more for $$ than anything else
Incorrect, at least, according to official answers and data. :)

The reason for the choice of 7905 over the 7805 was the lower "drop out voltage" on the 7905, meaning it can produce 5v at a lower input voltage than a comparable 7805. The way around that would be to start at a higher voltage -- which I think we know would mean more heat :)

Check the datasheets ... using Nat Semi parts as a guide.

LM7905: At 1A 1.1V (demanding at least 6.1v at input)
LM7805: At 1A 2.0V (demanding at least 7.0v at input)

That 0.9v must've made a difference to someone!

But yes, the consequences are a pain ...

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Re: New Oric Project. The OriClone-1

Post by kenneth »

A 5v positive regulator could be usable vith a 12v power with 1A diodes wired in serial, this voltage would feed the Scart without another tranformer.

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Re: New Oric Project. The OriClone-1

Post by Godzil »

mikeb wrote:
Fri Nov 06, 2020 5:44 pm
Godzil wrote:
Wed Nov 04, 2020 11:36 pm
Using the 7905 was a mistake, especially because using a 7805 would have not created any issue.
I really think that the choice of the 7905 was more for $$ than anything else
Incorrect, at least, according to official answers and data. :)

The reason for the choice of 7905 over the 7805 was the lower "drop out voltage" on the 7905, meaning it can produce 5v at a lower input voltage than a comparable 7805. The way around that would be to start at a higher voltage -- which I think we know would mean more heat :)

Check the datasheets ... using Nat Semi parts as a guide.

LM7905: At 1A 1.1V (demanding at least 6.1v at input)
LM7805: At 1A 2.0V (demanding at least 7.0v at input)

That 0.9v must've made a difference to someone!

But yes, the consequences are a pain ...
I know the datasheet, I also know that the 7905 can be cheaper in some conditions than the 7805.
Knowing that the common power supply (and official one) for the Oric were 9V one, this is non nonsensical to do that. In fact is it probably more easy to find a 7V power supply than a 6.1V

In fact for a linear power supply making a 6V, a 7V or a 9V do not change the price as long as the transformer is priced the same, so that's a weird excuse.

And yeah all official power supply were 9V:

http://www.48katmos.freeuk.com/psu.htm

Even the user manual (and service manual) are talking about 9V input:
Page 48: http://home.freeuk.net/48katmos/servman.pdf
Page 7: https://www.defence-force.org/computing ... _atmos.pdf

So that does not really hold up.

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