68kMLA Classic Interface

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68040 processor speed only 6 Mhz?
Posted by: djorud on 2023-04-28 15:06:33
Is this a capacitor issue? According to Norton Utilities test, the 68040 processor on my LC575 is operating at a speed of only 6 Mhz. Not 66, but only 6. Would this be indicative of a capacitor issue or possibly something else?
Posted by: Phipli on 2023-04-28 16:00:06
Is this a capacitor issue? According to Norton Utilities test, the 68040 processor on my LC575 is operating at a speed of only 6 Mhz. Not 66, but only 6. Would this be indicative of a capacitor issue or possibly something else?
Most likely just Norton misreporting, which usually means you have a version of Norton that is older than your computer. Run Norton System Info's CPU benchmark - how does it score?
Posted by: Iesca on 2023-04-28 16:38:36
Seems to me that any software meant for an 040 would be pretty much inoperable at 6MHz.
Posted by: ymk on 2023-04-28 17:15:03
Is the real time clock working correctly?
Posted by: djorud on 2023-04-28 17:22:45
Update: To double check the possibility of Norton being the problem, I switched out the questionable logic board with another LC575 board I had on hand that has been recently recapped. With the replacement board, Norton reports the 68040 running at 33 Mhz, as expected. Put the other board back in, and it reads as before, 6 Mhz. With that, it seems like it would be a logic board issue rather than a Norton problem.
Posted by: Phipli on 2023-04-28 22:42:55
Update: To double check the possibility of Norton being the problem, I switched out the questionable logic board with another LC575 board I had on hand that has been recently recapped. With the replacement board, Norton reports the 68040 running at 33 Mhz, as expected. Put the other board back in, and it reads as before, 6 Mhz. With that, it seems like it would be a logic board issue rather than a Norton problem.
Yes, but how fast did it benchmark?
Posted by: djorud on 2023-04-29 09:44:02
Norton Utilities benchmark rating for the LC575 is 6.87. To compare, my stock original Color Classic benchmark rating is 10. Modified with a 68040 accelerator, the Color Classic benchmark rating is 60. Seems like the LC575 should have been higher….
Posted by: djorud on 2023-04-29 09:47:25
Correction: the Color Classic is not “stock original”. It has an LC550 logic board. I added the accelerator to that when in “modified” state.
Posted by: Phipli on 2023-04-29 09:52:32
I'd suggest checking that these resistors are OK, and where you'd expect them to be :
Posted by: Phipli on 2023-04-29 09:55:07
After that you'll want to verify the path from the clock. The actual clock itself is OK because other hardware like video is derived from that, but if it is like the LC475, it goes... through two chips before the CPU I think?

Have you tried swapping in another CPU to test?
Posted by: Phipli on 2023-04-29 09:58:39
Can you provide a well lit, high resolution, close up photo of this area? It's where issues are most likely.

Has this board been recapped?

Screenshot_20230429_175658_Firefox.jpg
Posted by: djorud on 2023-04-29 14:23:38
Soldering on boards is not in my wheelhouse, so prefer someone else do those tasks for me. I have learned that my skills lie elsewhere. 🙂 Here are a closeup photos of the board in question. Also a couple of shots of test results: first, Norton, and second, Speedometer. Apologies for the bars on the photos. My phone camera has no manual controls to prevent their capture. But, the numbers can be seen if you squint a bit.
Posted by: Phipli on 2023-04-29 14:37:31
My phone camera has no manual controls to prevent their capture. But, the numbers can be seen if you squint a bit.
If you turn the screen brightness down it helps with taking photos.
Posted by: Phipli on 2023-04-29 14:40:42
Screenshot_20230429_223847_Firefox.jpg
Hum, I suggest getting all of your 68k boards with SMD caps recapped.

Looks like they're leaking already. The electrolyte is corrosive.
Posted by: djorud on 2023-04-29 15:14:45
Yes, had five of them done within the past few months. This is the only one remaining, having been kept as a spare should it be needed. Are you thinking the caps are responsible for the weak CPU performance or perhaps other components as well?
Posted by: Phipli on 2023-04-29 15:20:35
Yes, had five of them done within the past few months. This is the only one remaining, having been kept as a spare should it be needed. Are you thinking the caps are responsible for the weak CPU performance or perhaps other components as well?
The cap juice is corrosive and conductive, and capacitors missing their juice have reduced or no capacitance, leading to irratic behaviour. It might be the cause, and replacing them and cleaning the board might solve your issues, or perhaps it needs further repair.

But, its a good thing to start with because the condition of the board is only going to get worse until its done. This board has the look of one that has been in storage and then used for the first time in a while fairly recently? Lots of liquid, but not too much corrosion visible. Very much worth getting it sorted.
Posted by: djorud on 2023-04-29 16:05:18
Yes, it had been in dry, room temperature storage for more than ten years. Just found it recently and put it into my LC575 to see if it was functional or not. Turns out it it is, but slower than it should be by a factor of 10. Will be pursuing a good cleaning and recapping of it. Thanks for the help and advice in diagnosing this one. Much appreciated!
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