Furia addmem needs one reset with Amiga 600 Rev 1.1 (A300 board)

[turrican9]

So I recently got hold of an A600 Rev 1.1 (A300 motherboard) which I have repaired and is now fully working.

Using A Furia (the white PCB version) with SD to IDE and A604n. Funnily enough I had already removed C4 from this A604n from some previous troubleshooting with a Rev 1.5 board. C4 actually has to be removed for the A604n to boot with the older A600 (A300) motherboards. As they don't have a VBB Agnus.

Anyway, As far as I remember when using my Furia in my Rev 1.5 and Rev 2D motherboards and using the addmem in the startup sequence, classic workbench would boot up with the full mem from coldboot.

With this Rev 1.1 board it's booting without the full mem from coldboot when using addmem in startup. I have to do a quick reset and then it shows up with the full mem.

I'm guessing this is normal behaviour for this older revision motherboards. And it's not really a problem as it takes like 2 seconds with a quick reset before workbench is up again with the full mem.

I just wanted to know if other people with the Furia and older A300 rev 1 or rev 1.1 boards have the same thing happening?

[Superman]

I have exactly the same setup as you (mine is a Rev 1 A300 though) and it adds the memory first time.

[turrican9]

Originally Posted by Superman

I have exactly the same setup as you (mine is a Rev 1 A300 though) and it adds the memory first time.

Interesting. What is your startup line in boot sequence?

Here is mine: C:Furiatune addmem shadowrom cache on fpu on >NIL:

[Superman]

I have attached my startup sequence. I have everything on to the max

[turrican9]

Originally Posted by Superman

I have attached my startup sequence. I have everything on to the max

I see you have addmem last. I will try that and report back.

[turrican9]

Nope did not make a difference. Still have to give it one soft reset to get the memory added. Again, I don't think this happened on my Rev 1.5 and Rev 2D boards.

Maybe this is just a thing with the Rev 1.1 (A300 boards). You have the Rev 1.0

[Superman]

It’s strange for sure. Mines great as you can see from this video clip from cold boot.

[ Show youtube player ]

[turrican9]

Originally Posted by Superman

It’s strange for sure. Mines great as you can see from this video clip from cold boot.

[ Show youtube player ]

Very strange indeed. My board is working perfectly for everything I throw at it. Only thing I discovered was that I had to do a soft reset to get the full mem after cold boot.

I think I googled and found one guy telling the same thing in a post but I cannot find it again. So not sure.

[turrican9]

Think I found the thing I must have googled the other day.

First this post of a guy telling about a similar behaviour to mine. But he has more problems aswell.

Then this guy talking about a solution for 'the only showing 4MB at first boot' problem. Talking about replacing C611 and C613.



Interesting...

What makes this interesting is that I had to replace C305 which is also a ceramic cap. And it was bad and pulling voltage to the ground so my op amp did not get the voltage it needed. And C305 was right next to C306 which had leaked and caused corrosion on the solder joints of C305.

C611 and C613 are right next to C612 on either side of it which probably also had leaked prior to the recap. I will inspect this closer. I bet either one or both of these two ceramic caps are bad.

So that is probably the explanation as to why I get this strange behaviour. I'm glad I managed to find these forum posts again. Google is my friend.

So I donated C611 and C613 from my 2D board. Did not make a difference. Still will not show with full RAM from coldboot. Have to do a soft reset. The empty pads on the left side of C611 had fishy smell as I heated them up. So just aswell that I reworked the area around C612.

Could it be something wrong with the 555 timer perhaps?


The Solution:

Resistor R612 which is supposed to be 47K Ohms according to schematics and I measure that in my 2D board is only about 22K Ohms in my Rev 1.1 board. I have not found schematics for 1.1 boards but all other resistors in the 555 circuit are the same between 2D and Rev 1.1 board. And most other resistors I've seen so far on the board. So strange that R612 is only about 22K ohms in the 1.1 board. It has different markings than the 47K ohm resistor in the 2D board so I doubt it's out of spec. R612 is connected from VCC to C612 and pin 2 (TRIG) on the 555 timer. I wonder if this could be the cause as to why Furia will not activate the full mem after a coldboot.

I will try swapping it out for a 47K ohm and see what happens.

That was the issue! R612 was only 22K Ohm. Looked like it was this way from factory. Took the 47K Ohm resistor from the 2D board and soldered it in place of the 22K ohm in the 1.1 board and it's booting from coldboot and showing the full mem from the Furia without the need for a soft reset! Yes! Haha!

I believe smd resistor R612 in the Rev 1.1 board was actually marked with the number 243. That would equal to 24K Ohms. I measured close to 23K Ohms. 22.7K or something. Whilst the 47K Ohm in the 2D board and in the schematics are marked with the number 473 which of course is 47K ohms. Anyway, the 24K resistor in the 1.1 board was done by commodore with no doubt. Solder joints looked factory. If it was a mistake or if it was intended by commodore I don't know. Board was working fine with it. Appart from this little inconvenience with the Furia.

Here is the diagram I was using



Location of R612

[Boboo_SK]

@turrican9
GOOD JOB!!!

[Superman]

Great detective work

[turrican9]

Thanks.

Would be interesting to know if other people with Rev 1.1 boards has the same 24K resistor as R612.

@Superman I guess your Rev 1 board must have the 47K resistor at R612 since your Furia boots up with full mem from coldboot

[r.cade]

I think every single A300/A600 board is slightly different.

[amigappc]

I have the same situation with REV 1.3 A600 board.
It boots to 4mb and I have to reset to get full 9.5 MB

I checked, my R612 is 47K Ohm as it should be. So that solution is NOGO for me.

Originally Posted by turrican9

Thanks.

Would be interesting to know if other people with Rev 1.1 boards has the same 24K resistor as R612.

@Superman I guess your Rev 1 board must have the 47K resistor at R612 since your Furia boots up with full mem from coldboot

I got this message below from Boris Krizma.
However, my A600 did not suffer any leakage on that part of the board.
So now I wonder, should I try to replace those two caps, or live with one extra reset from now on.
It would be nice to be able to disable that 3 seconds hold CTRL+A+A function through firmware somehow.

From experience, I have found that some A600 boards are out of tune NE555 timing. When turned on, the C612 capacitor is charged, then flips and the processor starts. If this time circuit is disturbed, 4MB / 8MB will switch on incorrectly.
The NE555 timer and other parts are often damaged by electrolyte leakage. Often after ReCap the board does not come to the repair. It is necessary to deeper repair this circuit with NE555. It is recommended to replace C611 (100nF) and C613 (10nF) after replacing the capacitors it will time work properly.

This is appendix amiga 600 ;-)