Matchbox sized 6502 / Z80 / 6809 Co Pro

discussion of games, software, hardware & emulators relating to the Acorn Atom
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hoglet
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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby hoglet » Sun Oct 22, 2017 11:31 am

vanekp wrote:But it’s starting to look like I have either a faulty CoPro or it has the wrong firmware in it as I think I am correct in saying they use much the same code as in the Pi CoPro.

No, they are actually very different:
- PiTubeDirect is emulating the processors in software, so the "firmware" is built from a mixture of C and Assembler files.
- Matchbox is a real hardware implementation, so the "firmware" is an FPGA bitstream that is built from VHDL (and some Verilog) which are hardware descriptions (i.e. registers and logic)

In fact, there is pretty much nothing in common between the two implementations.

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby BigEd » Sun Oct 22, 2017 11:56 am

I'm not confident from that photo that this board has the extra bypass capacitors on it - and we know that those extra capacitors are needed for stable operation.
[Edit: oops, not so]

On the subject of the DIP switches, I think I remember Jason saying that they were not all soldered in the same way around, which does mean that On vs Off is a different direction on different boards. Just try all on and all off - one of them will be right.
Last edited by BigEd on Sun Oct 22, 2017 5:52 pm, edited 1 time in total.

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vanekp
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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby vanekp » Sun Oct 22, 2017 12:02 pm

Ahhh okay my bad. just they both have the same switch/*FX setting for the different CoPro's and also emulate all the same CoPro's.
Anyway I have sent a PM to Jason and asked to post the info here or via PM.

Thanks BigEd will see what Jason has to say, maybe he has shipped me an old version of the LxCoPro then.
And Dave’s explanation cleared up the switch settings.

Peter.

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby DutchAcorn » Sun Oct 22, 2017 12:12 pm

BigEd wrote:I'm not confident from that photo that this board has the extra bypass capacitors on it - and we know that those extra capacitors are needed for stable operation.


I thought only the first batch needed extra caps (red PCB)?
Paul

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby BigEd » Sun Oct 22, 2017 12:19 pm

Ah, my mistake. I saw 'Rev A' and thought it might be an early board. I see now that Dave has already said he does see the extra capacitors.

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby vanekp » Sun Oct 22, 2017 12:39 pm

I think your right Dave looking at the photo here:-
Image
there is a cap solder across one of the ic’s and on my board it looks like that is implemented on the board.
Last edited by vanekp on Sun Oct 22, 2017 1:19 pm, edited 1 time in total.

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1024MAK
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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby 1024MAK » Sun Oct 22, 2017 12:53 pm

This is not aimed at anyone, it's just me on my soapbox...

hoglet wrote:Matchbox is a real hardware implementation, so the "firmware" is an FPGA bitstream that is built from VHDL (and some Verilog) which are hardware descriptions (i.e. registers and logic)

I still think that the use of the term "firmware" is misleading. ROM, PROM, EPROM, EEPROM chips can be used in digital electronics where there are no MPU's, CPU's, micro-controllers, or processors (executing instructions) of any kind connected to it.

For example, some of the 1970s and 1980s era computers used a ROM/PROM/EPROM for the data for the pixels in character data in the video system. This data is not IMHO 'firmware'.

So in my eyes, firmware should only be used to describe a software program (or a collection of software routines) for a MPU/CPU/micro-controller/processor that is executed as code, but stored in a non-volatile long term storage chip like a ROM/PROM/EPROM/EEPROM.

With a FPGA, most of the data in the EEPROM is configuration information, so that the individual hardware gates can be set up to form the logical circuits required to "build" the wanted system. In this regard, it is no different to sending someone the schematic showing how to wire up and construct a single board computer by storing this information in a EPROM/EEPROM...

So I call the data for a FPGA configuration data.

Note that in the above text, you can substitute flash ROM for EEPROM.

<gets off soapbox (again!)>

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby vanekp » Sun Oct 22, 2017 1:30 pm

Elite running on Pi 3 CoPro for 3hrs now, not a single pixel out of place, so guess my hardware is fine :D
Now just to get to the bottom of the LxCoPro problem :wink:
Peter.

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby hoglet » Sun Oct 22, 2017 2:35 pm

vanekp wrote:Elite running on Pi 3 CoPro for 3hrs now, not a single pixel out of place, so guess my hardware is fine :D

I think all you can say for sure is that your system is fine for Pi Tube Direct. There are so many differences between the implementations of Pi Tube Direct and Matchbox that it's dangerous to generalise from this one data point. It could still be something amiss in the Beeb is causing the problem, but that the problem only manifests with the Matchbox. That's where being able to test in other Beebs would be useful. If it fails similarly in a second one, the it becomes much more clear cut.

Jason does usually soak test each board with Tube Elite, but I'm not sure for how long.

What's your plan now? Return it?

Dave

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby vanekp » Sun Oct 22, 2017 3:05 pm

I don't have another BBC to try it in so that is not an option.
Well I am waiting on Jason at this point to see what he has to say about it.
And think it was his last LxCoPro in stock, not sure if he is going to make more in the near future.

Edit to my post :- Just put the LxCoPro in, the BBC has been on for more than 4 hrs with Pi 3 CoPro (no problems)
It crashed a couple of time and now its been running for some 10 min already without a problem.
So something is very borderline.

Peter.

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby flynnjs » Sun Oct 22, 2017 5:43 pm

Peter's green board has all the required extra capacitors on it.
Only the red boards need extra caps added.

The only difference with this one is it is the first I have sent out
with Dave's latest bitware (there is a better word then firmware! ) :
LX9CoProCombined_20171007_0719_dmb

I did test this briefly in 6502 mode and also it booted DOS (I always
do this to ensure the 16bit RAM is working too).

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby vanekp » Sun Oct 22, 2017 6:06 pm

BBC runs fine with Pi 3 CoPro from cold ran elite for 5 hours on it.
If I start the BBC up cold with the LXCoPro it runs for about 5 min then crashes, once they have both warmed up then it appears to run okay has now been running for 3Hrs no problem but the BBC was already warm it did crash a few times at 1st till the CoPro had warmed up (it seems).
What is the way forward with this problem? as it’s not really usable or reliable like this.
I don't have another BBC to try it in only the Pi 3 with level converter, is there any other things I can try to resolve the problem?

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby flynnjs » Sun Oct 22, 2017 6:10 pm

You can return it for a bitware downgrade to see if that helps.

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby hoglet » Sun Oct 22, 2017 6:16 pm

flynnjs wrote:The only difference with this one is it is the first I have sent out
with Dave's latest bitware (there is a better word then firmware! ) :
LX9CoProCombined_20171007_0719_dmb

OK, that's very interesting.

There have only been 7 downloads of that version, so it's possible there is a stability issue.

I'll run the Tube Elite attract loop for the next couple of hours and see if I see any problems.

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby vanekp » Sun Oct 22, 2017 6:24 pm

Lets see what Dave comes up with 1st, take it your testing this in a BBC Model B Dave.
I take it it requires special software to program the device?

Peter.

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby hoglet » Sun Oct 22, 2017 6:39 pm

vanekp wrote:Lets see what Dave comes up with 1st, take it your testing this in a BBC Model B Dave.

Yes, and it's been OK for 30 minutes.
vanekp wrote:I take it it requires special software to program the device?

It needs Xilinx Impact (freely downloadable) plus a cable like this:
http://www.ebay.co.uk/itm/Xilinx-Platfo ... 2154533106

This will program pretty much any Xilinx based FPGA board.

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby vanekp » Sun Oct 22, 2017 7:26 pm

For something I may use once or twice.

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby hoglet » Sun Oct 22, 2017 7:35 pm

I know Trixter and RobC are running the latest firmware (that's what I choose to call it, as it's stored in non-volatile memory!)

Anyone else updated yet?

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby vanekp » Sun Oct 22, 2017 8:44 pm

Dave do you have a 6502 CPU in your BBC or a 65C02 ?
Have just put a 65C02 in mine (as that’s the only other processor I have) to test it so far so good (10min).
Will check again tomorrow when it has cooled right down to see.

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby hoglet » Sun Oct 22, 2017 9:14 pm

vanekp wrote:Dave do you have a 6502 CPU in your BBC or a 65C02 ?

I have a SY6502A date code 8337 (identical to yours which is a bit spooky)

Tube Elite has been running 3 hours now.
vanekp wrote:Have just put a 65C02 in mine (as that’s the only other processor I have) to test it so far so good (10min).
Will check again tomorrow when it has cooled right down to see.

That's also Interesting.

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby vanekp » Mon Oct 23, 2017 4:33 am

Switched it on this Am its been running without a problem for 30 min no crashing not even once with a 65C02 processor in the BBC.
and the 6502 I had in was new (couple of years ago now) as when I got the BBC it had a 65C02 in it which works just some games will not load as they use unofficial op codes.
pick the bones out of that :wink:

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby hoglet » Mon Oct 23, 2017 7:36 am

vanekp wrote:and the 6502 I had in was new (couple of years ago now) as when I got the BBC it had a 65C02 in it which works just some games will not load as they use unofficial op codes.

Can you post a photo of the markings on the underside of the 6502?

The 65C02 will be able to drive the data bus to higher levels, so maybe that's what's making the difference.

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby vanekp » Mon Oct 23, 2017 4:17 pm

Here are the photos of the chip both sides, the numbers on the bottom are a bit worn out hope you can read them.
20171023_175606.jpg

20171023_180426.jpg

As a matter of intrest I left the BBC on all day (soak test) with the 65C02 in and its still runnig the Elite test without any problems 12Hrs +.
What I find curious why does the LxCoPro work for most others and not for me? maybe I have something borderline on my BBC but what then?
Just checked again but don't have another 6502 to try only a 2nd 65C02 :(

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby hoglet » Mon Oct 23, 2017 5:07 pm

vanekp wrote:What I find curious why does the LxCoPro work for most others and not for me? maybe I have something borderline on my BBC but what then?

As ICs age, their timing characteristics and logic thresholds will change. So no two Beebs will be identical. Also, as ICs fail, they sometimes do that in very subtle ways. You only have to read some of the Beeb trouble-shooting threads to observe that in practice.

The Model B is a particularly harsh electrical environment, because the data bus is unbuffered and there are (I think) 18 loads. The tube is simply an extension of the data bus, without any additional buffering.

Correctly designed hardware systems should be resilient to this normal variation (i.e. there should be a certain amount of margin for error), but there will always be limits.

In your case, something is pushing the system as a whole over that limit, resulting in marginal operation.

It could be any number of things:
- power supply noise (due to degraded electrolytic capacitors)
- the SY6502A being out of spec timing wise
- some other component starting to fail in a way that places additional load on the data bus
- the particular Lx9CoPro being slightly more sensitive to noise

Recently when working with Dave Hitchins on the Electron AP5 which includes a Tube interface we saw some examples where the Matchbox would fail, yet PiTubeDirect worked perfectly. Changing almost anything in the system fixed the problem. e.g. using a shorter cable, removing an unrelated piece of hardware, leaving the system on for a while, etc. After a lot of debugging, this turned out to be crosstalk from the data bus switching inducing noise onto the reset line into the Matchbox, causing the Matchbox to very occasionally be randomly reset. I'll try to dig out a photo of this happening.

This is just an example, it's probably not what happening on your system.

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby hoglet » Mon Oct 23, 2017 5:30 pm

This was the photo of the reset related failure on the Electron:
IMG_0952.JPG


The top signal is nRST and the bottom signal is the regenerated Phi2.

nRST is dipping down to about 1.7v (maybe lower, because the scope probe will be dampening it). That's low enough to occasionally reset the Matchbox, which is what's causing the general unreliability.

The cause is basically crosstalk from other signals (probably the data bus) on the Matchbox cable. That's why it goes away when the Matchbox is plugged in directly.

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby flynnjs » Mon Oct 23, 2017 6:22 pm

Reminds me, I've seen lots of funnys with IDE cables that have been repurposed, including
it working with the cable one way around but not the other, I kid you not!
I too would recommend your testing with it directly connected under the keyboard
rather than using a ribbon.

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby vanekp » Mon Oct 23, 2017 6:25 pm

The only other hardware I have is this Rom/Ram board I got off fleBay:-
20171023_193215RomRamBoard.jpg

This is the ripple I see on the 5v at the user port about 15mv
20171023_195414UserPort.jpg

Across the Rom Socket also around 15mv
20171023_200004RomChip.jpg

And across the smothing cap where the power comes in on the middle connectors of the main board.
20171023_195618C26.jpg

as you say it could be many diffrent things.

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby 1024MAK » Mon Oct 23, 2017 7:03 pm

Temperture can play a role in lots of marginal cases of strange symptoms. As the temperature goes up, so bipolar transistors conduct more.

And as the temperature changes, so the actual switching levels will change slightly. Also the switching speed of semiconductors is affected.

In the case of modern expansions, these will use newer chips, and this can affect or be affected by slight differences. As modern CMOS chips have different switching levels compared to TTL and 5V NMOS chips.

Modern CMOS chips also are far more aggressive in the speed (rate of change) that they drive their outputs at.

As Dave says above, from the outside, the design of the Beeb appears great, but the poor old 6502 outputs are driving more of a load than the chip was intended to drive.

Even the Z80 was supposed to be connected to line driver buffer chips, rather than directly driving the bus like in most home computers...

Mark
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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby BigEd » Mon Oct 23, 2017 7:17 pm

Don't forget the mystery of the RP1 pull-down resistors, acting as virtual Furber Fingers. (The Beeb's design was a rush job, tweaked until it seemed to work.)

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Re: Matchbox sized 6502 / Z80 / 6809 Co Pro

Postby vanekp » Mon Oct 23, 2017 8:07 pm

Yet they are very reliable machines.


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