Partially Working A4000 - Help!!

discuss the archimedes & risc pc, peripherals and risc os/risc os on pi
User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Partially Working A4000 - Help!!

Post by hoglet » Thu Jul 04, 2013 7:22 pm

Hi all,

I've just received delivery of a A4000 from Ebay, that seems to have a few issues :lol: I've never owned an Archimedes, so I'll need a bit of help with this.

I've got it connected to:
- a modern LCD monitor, which seems to be happy to display 640x480@60Hz
- PS2 mouse/keyboard via a experimental PIC based adapter (see this thread

It sort of seems to be working, but generally seems to crash during the boot phase (usually with Error: UndefinedInstruction) and I end up at the supervisor prompt. Doesn't seem to be any battery damage.

At this point, sometimes the keyboard works, and I can type in * Commands. For example, I've managed to format and verify a floppy, so I know the floppy drive is working. But the floppy does not always seem to initialize properly.

It had an 80MB hard drive which I think is probably broken, so I've disconnected this.

Just once, the desktop started to launch, but crashed out.

Here's a few pictures..

The A4000 itself:
IMG_0197.JPG
IMG_0197.JPG (454.85 KiB) Viewed 2493 times
The PS2 Mouse/Keyboard adapter:
IMG_0196.JPG
IMG_0196.JPG (317.44 KiB) Viewed 2493 times
The supervisor screen, note the Error at the top, one of several I see:
IMG_0199.JPG
IMG_0199.JPG (487.68 KiB) Viewed 2493 times
Another failure mode:
IMG_0203.JPG
IMG_0203.JPG (253.09 KiB) Viewed 2493 times
Any ideas where I should go from here?

Anyone have an image of the diagnostics disk?

Dave

User avatar
danielj
Posts: 7962
Joined: Thu Oct 02, 2008 5:51 pm
Location: Manchester
Contact:

Re: Partially Working A4000 - Help!!

Post by danielj » Thu Jul 04, 2013 7:42 pm

Firstly, switch it on holding delete. This will reset the CMOS. Have you changed the CMOS battery?

d.

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Thu Jul 04, 2013 7:53 pm

danielj wrote:Firstly, switch it on holding delete. This will reset the CMOS. Have you changed the CMOS battery?

d.
I've tried the Delete reset thing, but it made no difference. I'm not 100% convinced that the PS2 keyboard adapter is passing this thought. Is there anything other way to reset the CMOS RAM?

I've got one of these, but not fitted it yet:
DSC0250813341509664f8587362a282.jpg
DSC0250813341509664f8587362a282.jpg (43.77 KiB) Viewed 2484 times
http://spiratronics.com/nickel-metal-hy ... 50mah.html

I'll probably try this next....

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Thu Jul 04, 2013 7:56 pm

I think a found a zip image of the diagnostics disk on here:
http://www.lewisgilbert.co.uk/archiolog ... discs.html
Test-Disc.zip
(620.04 KiB) Downloaded 99 times
I just need to figure out how to
- Convert it to an ADFS image
- Write it to a 3.5" ADFS Floppy

Any suggestions?

A beeb and a serial cable?

I'm good with Linux as well.....

Dave

User avatar
flaxcottage
Posts: 4025
Joined: Thu Dec 13, 2012 8:46 pm
Location: Derbyshire
Contact:

Re: Partially Working A4000 - Help!!

Post by flaxcottage » Thu Jul 04, 2013 9:02 pm

The way I did this was;

1. save the zip file to a 1.44Mb PC format floppy disc
2. read the file into my A3020
3. used !SparkFS to extract the Acorn files from the zip
4. wrote the files to an Archimedes format 800K floppy
5. read the Archimedes floppy using OmniFlop to create a digital image of the physical disc which I called TestDisc.adl
6. zipped the .adl image into a zip file posted below.

To extract the disc from the image you will need OmniFlop to write the .adl image to a formatted 800K E format disc from your A4000 (you say you have a formatted disc) or use OmniFlop to format a DD (not HD) floppy to 800K E format and then copy the data from the .adl file to the disc.

Hope it works for you.

Cheers,
John

If all goes well you will have a real, physical Archimedes format test disc.

Good luck.

PS. Thanks for this. It gave me an excuse to get my Archimedes out. :D :D :D
Attachments
TestDisc.zip
(231.05 KiB) Downloaded 84 times
- John

Image

User avatar
IanB
Posts: 539
Joined: Sun Sep 04, 2011 8:28 pm
Location: South Wales
Contact:

Re: Partially Working A4000 - Help!!

Post by IanB » Thu Jul 04, 2013 10:17 pm

hoglet wrote: PS2 mouse/keyboard via a experimental PIC based adapter

I've tried the Delete reset thing, but it made no difference. I'm not 100% convinced that the PS2 keyboard adapter is passing this thought. Is there anything other way to reset the CMOS RAM?
Dave
Wow, that was a quick test of the PS/2 adapter and on a PCB too!

I hadn't previously tested any of the keydown on powerup options but having tried them now, you are correct that they don't work with the adapter so I'll fix that in the next beta release.

Ian

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Thu Jul 04, 2013 10:55 pm

IanB wrote: I hadn't previously tested any of the keydown on powerup options but having tried them now, you are correct that they don't work with the adapter so I'll fix that in the next beta release.
It was hard for me to tell whether R break was doing anything. I was sort of convinced that it was.

I look forward to the next beta release. The seems to be mostly working. Occasionally I'll get one of the error lights coming on, but that may be the dodgy A4000.

So, part of my problems might just be messed up CMOS settings.

Is there any other way to reset these?

Dave
Last edited by hoglet on Thu Jul 04, 2013 11:05 pm, edited 1 time in total.

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Thu Jul 04, 2013 10:59 pm

flaxcottage wrote: To extract the disc from the image you will need OmniFlop to write the .adl image to a formatted 800K E format disc from your A4000 (you say you have a formatted disc) or use OmniFlop to format a DD (not HD) floppy to 800K E format and then copy the data from the .adl file to the disc.
This worked perfectly - so I now have a test disk.

Unfortunately, the machine is not quite reliable enough to run it.

When I do get to the Supervisor * Prompt with a working drive, entering !Boot seems to start loading the test disk, but then I just get a blank screen. Maybe it's changing to one of the lower scan rate 15KHz modes that modern LCD monitors can't handle. I'll need to dig out an old scan convertor I have.

Dave
Last edited by hoglet on Thu Jul 04, 2013 11:05 pm, edited 1 time in total.

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Thu Jul 04, 2013 11:03 pm

danielj wrote:Firstly, switch it on holding delete. This will reset the CMOS. Have you changed the CMOS battery?
I've now changed the CMOS battery, but I'm not 100% sure whether I'm able to properly reset the CMOS settings, because Ian says the Delete while Powering Up may not actually be getting through his protocol converter.

Is it possible that duff CMOS settings could cause the problems I'm seeing? What exactly do these settings control? Is it things like memory timings?

A few times now it has actually booted successfully to the RISC OS Desktop, and once there it seems pretty reliable, rather than crashing immediately.

Thanks everyone for the help so far.

Dave

User avatar
paulv
Posts: 3854
Joined: Tue Jan 25, 2011 6:37 pm
Location: Leicestershire
Contact:

Re: Partially Working A4000 - Help!!

Post by paulv » Fri Jul 05, 2013 12:38 am

hoglet wrote:A few times now it has actually booted successfully to the RISC OS Desktop, and once there it seems pretty reliable, rather than crashing immediately.

Thanks everyone for the help so far.
If you have a Uniboot type sequence on the HDD, hold shift whilst resetting to stop it from running. It may be that your particular combination of modules aren't quite as stable as the versions in the RISC OS ROM. You will at least get a stable desktop by bypassing any boot sequence and rule out any other issues. If it's still not stable then we need to look elsewhere.

Paul

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Fri Jul 05, 2013 8:05 am

paulv wrote:[If you have a Uniboot type sequence on the HDD, hold shift whilst resetting to stop it from running. It may be that your particular combination of modules aren't quite as stable as the versions in the RISC OS ROM. You will at least get a stable desktop by bypassing any boot sequence and rule out any other issues. If it's still not stable then we need to look elsewhere.
There is no hard drive at present.

Once I get to the desktop, it seems 100% stable. It's just that 9 times out of 10 it will crash out before it reaches the desk top.

Is there a program that will reset the CMOS to the factory settings? I'm not sure whether the keyboard adapter I have is passing R powerup break through correctly. Ian thinks it probably isn't.

Dave

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Fri Jul 05, 2013 8:45 am

One more small step forward....When the test disk goes black, I've confirmed it is actually changing to a menu, but in a mode that my LCD monitor doesn't support. My GBS8200 doesn't lock to this properly either. Time to make a DSUB -> SCART Cable.

Dave

User avatar
danielj
Posts: 7962
Joined: Thu Oct 02, 2008 5:51 pm
Location: Manchester
Contact:

Re: Partially Working A4000 - Help!!

Post by danielj » Fri Jul 05, 2013 9:45 am

hoglet wrote:One more small step forward....When the test disk goes black, I've confirmed it is actually changing to a menu, but in a mode that my LCD monitor doesn't support. My GBS8200 doesn't lock to this properly either. Time to make a DSUB -> SCART Cable.

Dave
The sync on the arc doesn't come out of the pin you think it should...

http://www.stardot.org.uk/forums/viewto ... 026#p53026

That might help :) - I have had an A3020 which is basically the same machine outputting through a 8200...

d.

steve3000
Posts: 2160
Joined: Sun Nov 25, 2012 12:43 am
Contact:

Re: Partially Working A4000 - Help!!

Post by steve3000 » Fri Jul 05, 2013 10:11 am

I expect your monitortype is set incorrectly (as a 'multisycn' monitor, rather than a SVGA/VGA screen) and so the test disc is entering a 15KHz mode...either that or your test disc is for an early Archimedes and not compatible with the A4000.

To rule out the first, try booting to supervisor, using your LCD screen, then type:

*Configure Monitortype 4

This sets the CMOS monitor settings to SVGA/VGA, and by doing this, RISC OS will not allow any (correctly written) programmes to enter 15KHz screen modes any more.

Now reset and try your test disc now and it should be visible.


Note: if you later change to use a SCART cable, you'll need to change the MonitorType to 0, to enable 15KHz modes again.

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Fri Jul 05, 2013 10:45 am

Thanks for the suggestions, will try this evening.

This is fun! :lol: :lol: :lol:

Dave

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Fri Jul 05, 2013 6:49 pm

A bit more tinkering....

*CONFIGURE MONITORTYPE 4 allowed me to get a bit further with the test disk. I now get a menu in VGA mode, but when I try to run an individual test (e.g. memory test) it will crash with an Illegal Instruction (or and address exception).

I've configured it to boot into Basic (*CONFIGURE LANGUAGE 18) and have written a simple pseudo random RAM test. This is running now, so we'll see how things go over the next hour.

I'm a bit flummoxed with this. Once I'm in Basic, things seem quite stable. I'm beginning to think this might be a bit trickier to fix than I first thought.

Looking closely around the battery areas, there are some signs that the battery has leaked at some point (i.e. a couple of the traces are the copper oxide coloured), but it does seem very localized.

Can anyone suggest any other diagnostics programs that I could try running?

Dave

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Fri Jul 05, 2013 7:52 pm

Memory test ran for an hour or so without error.

However, I was trying a few other things from BASIC, and changing Screen mode does seem to induce a failure very quickly.

For example, if I type MODE 12 a few times, I'll eventually get an error like:

Internal error: undefined instruction at &0381CF90

This is the same location I frequently see a failure on during the boot sequence.

The A4000 motherboard is labelled:

0194,600 Iss. 1
ED3270

Any known issues with this version?

I did find this:
http://acorn.riscos.com/fco/fco2028.txt

The ROMS are labelled:

0296,061-02
(C) AND TM ACORN 1992
RISC OS 3
ROM 1
RL080

0296,062-02
(C) AND TM ACORN 1992
RISC OS 3
ROM 2
RL080

Which I think is RISCOS 3.11, the expected version for the A4000, correct?

Dave

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Fri Jul 05, 2013 8:54 pm

Digging in to the most common error I am seeing:

Internal error: undefined instruction at &0381CF90

Disassembling this, the instructions look just fine.

So, I'm wondering if this is starting to point the finger at something like excessive power supply noise, maybe down to old electrolytic capacitors not doing their job any more.

I might start replacing some of these.

Dave

User avatar
1024MAK
Posts: 9906
Joined: Mon Apr 18, 2011 5:46 pm
Location: Looking forward to summer in Somerset, UK...
Contact:

Re: Partially Working A4000 - Help!!

Post by 1024MAK » Fri Jul 05, 2013 9:00 pm

You can use a oscilloscope to check the power supplies for ripple and noise, or failing that, use a good multimeter (one that has a wide ac bandwidth and reads true RMS) on the mV ac range.

Mark

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Fri Jul 05, 2013 9:42 pm

1024MAK wrote:You can use a oscilloscope to check the power supplies for ripple and noise, or failing that, use a good multimeter (one that has a wide ac bandwidth and reads true RMS) on the mV ac range.]
Measured with an Oscilloscope, there is about 25mV pk-to-pk ripple on the +5V rail. I doubt this is causing the problem, so back to square one again.

Dave

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Fri Jul 05, 2013 10:58 pm

Another question.....

Any idea what supplies the A4000 needs to boot, and whether there are any sequencing requirements?

The PSU has +12V, -12V and +5V rails. Looking at the schematics, -12V doesn't seem to be used for much.

I was thinking of wiring it up to my Bench power supply (which does 0-15V at up to 4A, times two), and seeing if the fault showed any sensitivity to supply voltage, by varying the +5V rail between, say 4.8 and 5.2 volts.

Dave

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Sat Jul 06, 2013 9:02 am

It gets stranger and stranger :shock: :shock: :shock:

I'm running it off my bench power supply now.

At 5V, the behaviour is very similar.

At 5.2V (as high as I dare), it's not any better.

But if I reduce the voltage to 4.4V (way too low I know!!!), the problem is significantly reduced.

My test program is:
10 I=0
20 MODE 12
30 PRINT I
40 I=I+1
50 GOTO 20

At 5V, this will crash on the first couple of iterations.

At 4.5V, this will run for ~50 iterations before crashing.

Not sure if this help, but it's another data point....

Dave

steve3000
Posts: 2160
Joined: Sun Nov 25, 2012 12:43 am
Contact:

Re: Partially Working A4000 - Help!!

Post by steve3000 » Sat Jul 06, 2013 9:54 am

hoglet wrote:So, I'm wondering if this is starting to point the finger at something like excessive power supply noise, maybe down to old electrolytic capacitors not doing their job any more.
My A4000 has so much noise on its power lines it keeps the house next door up at night. I really should replace its caps...

Your fault, however, does seem rather random, but I'm sure we can narrow it down a little further.

What mode do you start up in (type 'PRINT MODE')?

When you enter BASIC on start up, how much memory is free? (it should be around 1600k). If you do not change screen mode, and just test this memory, is everything fine - with no crashing?

Assuming the computer is stable after the memory test - try changing mode once - to the same mode you've started in, and rerun the tests. Is it still stable?

Next try changing to a different mode, say Mode 12 or Mode 8. Now rerun the test... repeat this with a few different modes, eg. 25, 27, 15...

When it does crash, is this on the Mode change itself or some time after?

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Sat Jul 06, 2013 10:33 am

Hi Steve,
steve3000 wrote: What mode do you start up in (type 'PRINT MODE')?
Mode 27
steve3000 wrote: When you enter BASIC on start up, how much memory is free? (it should be around 1600k). If you do not change screen mode, and just test this memory, is everything fine - with no crashing?
1683708 bytes
steve3000 wrote: Assuming the computer is stable after the memory test - try changing mode once - to the same mode you've started in, and rerun the tests. Is it still stable?

Next try changing to a different mode, say Mode 12 or Mode 8. Now rerun the test... repeat this with a few different modes, eg. 25, 27, 15...

When it does crash, is this on the Mode change itself or some time after?
I can make it crash easily, regardless of the mode:

10 CLS
20 GOTO 10

It seems that an intense burst of RAM writes (such as clearing the screen)
is somehow affecting instruction execution from the OS ROM, causing an the processor to think it's seeing an undefined instruction.

As you suggest, I really need to get hold of a simple memory test program, ideally written in assembler.

Can anyone suggest one?

Keep the suggestions coming

Dave

steve3000
Posts: 2160
Joined: Sun Nov 25, 2012 12:43 am
Contact:

Re: Partially Working A4000 - Help!!

Post by steve3000 » Sat Jul 06, 2013 10:57 am

hoglet wrote:I can make it crash easily, regardless of the mode:

10 CLS
20 GOTO 10
Yikes, that's not good at all.
hoglet wrote:It seems that an intense burst of RAM writes (such as clearing the screen) is somehow affecting instruction execution from the OS ROM, causing an the processor to think it's seeing an undefined instruction.
RISC OS performs a simple single pass memory test on start up (before displaying 2048 k), so at that stage it certainly thinks your memory is ok.

Also, there is fairly regular RAM access going on in the background of RISC OS, as a multitude of interrupt processes are present.

If you leave the computer without doing anything, does it crash eventually?

Also, does sound work (VDU 7)?

And does the pointer display correctly (*Pointer On)?

User avatar
1024MAK
Posts: 9906
Joined: Mon Apr 18, 2011 5:46 pm
Location: Looking forward to summer in Somerset, UK...
Contact:

Re: Partially Working A4000 - Help!!

Post by 1024MAK » Sat Jul 06, 2013 11:18 am

Are the OS ROM sockets okay? It is possible a high resistance connection is causing problems. While you have the ROMs out, check for damage to the board around the sockets.

Mark

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Sat Jul 06, 2013 5:18 pm

Hi Steve,

Thanks for sticking with me!
steve3000 wrote:Also, there is fairly regular RAM access going on in the background of RISC OS, as a multitude of interrupt processes are present.

If you leave the computer without doing anything, does it crash eventually?
It doesn't seem to crash when just left idling, but I'll leave it on overnight tonight.
steve3000 wrote: Also, does sound work (VDU 7)?
Sound works OK.
steve3000 wrote: And does the pointer display correctly (*Pointer On)?
*POINTER 1

seems to work.

I've just written a BASIC Memory Test

10 @=0
15 I%=1
20 S%=LOMEM
30 E%=HIMEM-&100
35 PRINT "TESTING MEMORY FROM "~S%" TO "~E%
40 REPEAT
50 X%=RND(-I%)
60 PRINT "WRITING: "I%
70 FOR A%=S% TO E% STEP 4
80 !A%=RND
90 NEXT
100 X%=RND(-I%)
110 PRINT "READING: "I%
120 FOR A%=S% TO E% STEP 4
130 IF !A%<>RND PRINT "ERROR AT"~A%
140 NEXT
150 I%=I%+1
160 UNTIL FALSE

It's testing &009008 TO &0019FF00, and has done three passes so far.

I'm going to leave this running for the next couple of hours and see how it goes.

What ever is wrong, is very selective :lol: :lol: :lol:

Dave

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Sat Jul 06, 2013 5:24 pm

Hi Mark,
1024MAK wrote:Are the OS ROM sockets okay? It is possible a high resistance connection is causing problems. While you have the ROMs out, check for damage to the board around the sockets.
The OS ROM sockets are very clean, with no signs of corrosion. Same goes for the OS ROM pins. I also can't see any damage to the board - it all looks in very good nick, albeit slightly grubby in places.

Dave

User avatar
hoglet
Posts: 9096
Joined: Sat Oct 13, 2012 7:21 pm
Location: Bristol
Contact:

Re: Partially Working A4000 - Help!!

Post by hoglet » Sat Jul 06, 2013 8:09 pm

Memory test has been running for 2.5 hours. 107 iterations and no errors.

Seems it is much more sensitive to screen memory being written to.

Dave

steve3000
Posts: 2160
Joined: Sun Nov 25, 2012 12:43 am
Contact:

Re: Partially Working A4000 - Help!!

Post by steve3000 » Sat Jul 06, 2013 8:13 pm

hoglet wrote:Hi Steve,

Thanks for sticking with me!
No problem, it's always fun trouble-shooting these old machines.

Sound and mouse pointer working is another good sign - both make intensive use of memory access to the first 1/2Mb of memory during interrupts, so if anything was wrong there, then the computer would crash.

Your memory test has confirmed the other 1.5Mb is good, so the problem isn't with the RAM.

But just if you want to check... the screen memory ends at &2000000, Mode 27 is 640*480/2 bytes large, so subtract this number from &2000000, then run your memory test over the screen - and watch the nice colours ;)

...but I think this will be fine, based on the sound and pointer result.

If it is ok, I'd have to go with Mark's hint about the ROMs now.

Take the two OS ROMs out, and put back in (while 'wiggling' them a bit in the socket). This will remove any surface corrosion - you may not even notice a low level of corrosion when looking. I really should have thought about that before - I had a BBC B which was always playing up with random freezes, but after much frustration inspecting and removing/replacing/refitting pretty much every chip on the board, just taking the BASIC rom out and putting it back in again solved the problem...

Post Reply

Return to “32-bit acorn hardware”