CT60 replacement flash chip

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wthorbjo
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CT60 replacement flash chip

Post by wthorbjo »

As chronicled in a previous thread, my CT60 Falcon refuses to boot in 060 mode, but boots and works fine in 030 mode. I also cannot program the flash ROM with any version of TOS, using any version of FLASH060.PRG.

I'm able to program and verify ABE and SDR without issues, both using FLASH060.PRG and Xilinx tools from a PC, so I believe the CPLD chips are OK.

By process of elimination, I concluded that the CT60 flash chip likely was bad. I replaced the flash chip with what I believe is an equivalent part from a different supplier (original chip AM29F800BB made by AMD, replacement is M29F800FB made by Alliance Memory). AMD stopped manufacturing this part many years ago, so this was as close as I could get.

Now I have a new problem, which hopefully is a sign of progress: When I try to flash TOS using FLASH060.PRG, I now get the error message "Unknown flash device! ($21CD21CD)" (with the old chip I got "Error while programming flash!").

I believe that FLASH060.PRG checks the ID code of the flash chip before programming, and since the new chip has a different ID code it refuses to program it. The datasheets indicate that the new chip works the same as the old chip, so hopefully it's just a question of patching FLASH060.PRG to recognize the new ID code. I've looked through the source code for FLASH060.PRG, but I don't know how to make the appropriate changes and re-compile. Can someone help with this?

I might also be barking up the wrong tree entirely, so any other troubleshooting suggestions are welcome!
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Re: CT60 replacement flash chip

Post by mpattonm »

Do you have an access to some EPROM programmer? I could send you a binary image of fully configured ROM. And/or try flash060.prg from CT60e
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Re: CT60 replacement flash chip

Post by sety »

wthorbjo wrote: Fri Apr 01, 2022 8:53 pm Now I have a new problem, which hopefully is a sign of progress: When I try to flash TOS using FLASH060.PRG, I now get the error message "Unknown flash device! ($21CD21CD)" (with the old chip I got "Error while programming flash!").
Are you using the correct version of FLASH060.PRG? The flash rom in the ct60's design changed at some stage due to part availability and there are different versions of FLASH060.PRG out there.

I had the exact same issue when I swapped out my flash rom chip. After a delicate job like that, it was very easy to spend a long time thinking I'd made a mistake when the problem was actually something very simple.
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Re: CT60 replacement flash chip

Post by sety »

PS: Just looked at mine and the 29F800 I used is made by Macronix so can confirm aftermarket works.
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Re: CT60 replacement flash chip

Post by mpattonm »

Alternatively, if you have no luck flashing it in the system, I can send you pre-programmed chip.
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wthorbjo
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Re: CT60 replacement flash chip

Post by wthorbjo »

mpattonm wrote: Fri Apr 01, 2022 9:52 pm Do you have an access to some EPROM programmer? I could send you a binary image of fully configured ROM. And/or try flash060.prg from CT60e
I have a programmer, but no suitable adapter for the TSOP-48 package. I can easily get a breakout PCB, though.
mpattonm wrote: Sat Apr 02, 2022 6:41 am Alternatively, if you have no luck flashing it in the system, I can send you pre-programmed chip.
Honestly, if you have a chip on hand, that would be extremely helpful! Sending you a PM.
sety wrote: Sat Apr 02, 2022 2:23 am Are you using the correct version of FLASH060.PRG? The flash rom in the ct60's design changed at some stage due to part availability and there are different versions of FLASH060.PRG out there.

I had the exact same issue when I swapped out my flash rom chip. After a delicate job like that, it was very easy to spend a long time thinking I'd made a mistake when the problem was actually something very simple.
Good point! I've tried all the different versions I could find, including the FLASH060.PRG from Didier's original 1.03c bundle, the one from the 2.01 (CTPCI) bundle, Willy's 1.05, Mikro's "reloaded" version, and the CT60e bundle. All with the same result.
sety wrote: Sat Apr 02, 2022 2:34 am PS: Just looked at mine and the 29F800 I used is made by Macronix so can confirm aftermarket works.
That's very interesting! I went back and studied the different datasheets again, and it turns out that at least the low byte of the chip ID should be the same for all the varieties (0x58), but from what I can see the high byte and manufacturer codes vary. Looking at the most recent source from Mikro's github, the comments indicate that the program only should be looking at the low byte anyway, so there might be something else going on here...

BTW, I've checked the three bus driver ICs on the CT60 with my oscilloscope, and as far as I can determine the bus signals are getting through. I've also tried replacing the chips with new parts, but nothing changed. I've checked the clock signal too, and tried several different options (CTCM, Exxos' clock module, 66MHz crystal). I've wondered if the 68060 might have been damaged somehow, but I don't think that would have affected the ability to flash the boot ROM.

Thanks everyone for the very good suggestions! Any further ideas are most welcome.
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Re: CT60 replacement flash chip

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Update: After double-checking with a multimeter today, I've found that at least six PCB traces are broken (or cut?) under the 29F800 flash chip. According to the schematics, these are address lines. Clearly, there's more going on here than just a bad ROM chip - I assume these lines should be connected as per the CT60 schematic. I've removed the new flash chip from the board, and now I'm contemplating how to repair the PCB traces, if that's even possible. I have a good soldering station, but no microscope. My hands aren't the steadiest either. Any tips or tricks?

Image

Looks like this board has led a rough life. I remember sending it back to Rodolphe Czuba for repairs shortly after I bought it, many years ago now, but I can't remember what he said he fixed. Edit: I found an old email from Rodolphe:
> After a long delay and many investigations on the board, I finally found the problem... on the PCB under the flash. I replaced the flash too.
The board worked fine for a while after I got it back, though it didn't get very much use. I'm wondering if the same issue has re-surfaced...
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Re: CT60 replacement flash chip

Post by ragnar76 »

My first shot to fix this would be a thin wire but maybe a bit of flux, some solder and dragsolder the pads could help too.

have you noticed that the resistor/diode is burned too and that the 6th and 7th pad (counted from bottom) doesnt look good?
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Re: CT60 replacement flash chip

Post by wthorbjo »

ragnar76 wrote: Sat Apr 02, 2022 9:40 pm have you noticed that the resistor/diode is burned too and that the 6th and 7th pad (counted from bottom) doesnt look good?
The resistor is actually ok, it’s just covered in a blob of flux residue. There’s several pads that are a little worse for wear, but with a little care they should be ok. This board was not made for repeated soldering and unsoldering, and it’s getting pretty fragile. Hopefully it’s still salvageable, otherwise I’ll have to go looking for a new CT60 PCB. I’ve heard rumours that someone will be making them available pretty soon. :wink:

Hopefully that precious rev. 6 68060 is still okay!
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Re: CT60 replacement flash chip

Post by sety »

You could try offsetting the flash chip to the right so that the left legs cover both the pad and the trace. It looks like this may have been how Radolphe fixed it as the traces have been tinned. You would want to be accurate though.

Alternatively you could just run some bodge wires (40awg enameled cu) to the vias perhaps joining back to the traces just North of the flash chip (easier but won't look as nice)
wthorbjo wrote: Sat Apr 02, 2022 8:10 pm My hands aren't the steadiest either. Any tips or tricks?
Probably not the most responsible advice, but I find a few stiff whiskies makes soldering a lot easier.
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Re: CT60 replacement flash chip

Post by TheNameOfTheGame »

sety wrote: Sun Apr 03, 2022 12:59 am Y
wthorbjo wrote: Sat Apr 02, 2022 8:10 pm My hands aren't the steadiest either. Any tips or tricks?
Probably not the most responsible advice, but I find a few stiff whiskies makes soldering a lot easier.
haha I hear you brother. Although I substitute liqour for a few cold ones. I solder much better then. :D
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Re: CT60 replacement flash chip

Post by mpattonm »

Alternatively, you could jumper wire these broken tracks from the via eyelets (left to the flash IC) to the IC5 (middle 74LV245) legs. That should be much easier than to spend eternity trying to solder jumper these tracks below an actual flash IC.
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Re: CT60 replacement flash chip

Post by wthorbjo »

Quick update: I was able to read the contents of the original flash chip from my CT60 using an EPROM programmer. The chip seems to be working, and the data on it seems to be valid. Definitely looks like the broken PCB traces are the problem. I have a couple of ideas for repairing them, and will report back. Thanks again to everyone for the help and suggestions.
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