Logic Board - Macintosh SE Reloaded

JDW

JDW

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@Kris92
@Kai Robinson

It would be greatly appreciated if one of you could please post photos or drawings of the precise location on the SE Reloaded motherboard and the exact pins that need to be either cut or jumpered, including the place where the jumper wire needs to be soldered to, taking into consideration that shorter leads are best.

If those 2 problems have indeed been 100% confirmed by Kai to affect all SE Reloaded motherboard revisions, I need to get this information out to people in a crystal clear and easy to understand way. I just don’t have time right now to analyze the board and make those photos or drawings myself.

Thank you.
 
Kris92

Kris92

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Jun 1, 2026
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JDW said:
@Kris92
@Kai Robinson

It would be greatly appreciated if one of you could please post photos or drawings of the precise location on the SE Reloaded motherboard and the exact pins that need to be either cut or jumpered, including the place where the jumper wire needs to be soldered to, taking into consideration that shorter leads are best.

If those 2 problems have indeed been 100% confirmed by Kai to affect all SE Reloaded motherboard revisions, I need to get this information out to people in a crystal clear and easy to understand way. I just don’t have time right now to analyze the board and make those photos or drawings myself.

Thank you.
Click to expand...
I will post a picture as soon as my board will be assembled (1 or 2 weeks maybe). But only one issue can be fix. The other one can't be fixed and is not critical...if you don't reverse the internal SCSI cable...
 
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JDW

JDW

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Kris92 said:
The other one can't be fixed and is not critical...if you don't reverse the internal SCSI cable...
Click to expand...
It’s actually pretty critical because I have accidentally reversed the cable I was inserting on the internal SCSI connector on my SE/30 more than once in the past.

I try to be extremely careful about that now, but since it’s happened more than once before, and since I am getting older and feel like I’m losing my mind at times, it’s not beyond the realm of the possible that it would never happen again.

in any case, I look forward to your photo to describe the one area that can be repaired.
 
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Kris92

Kris92

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JDW said:
It’s actually pretty critical because I have accidentally reversed the cable I was inserting on the internal SCSI connector on my SE/30 more than once in the past.

I try to be extremely careful about that now, but since it’s happened more than once before, and since I am getting older and feel like I’m losing my mind at times, it’s not beyond the realm of the possible that it would never happen again.

in any case, I look forward to your photo to describe the one area that can be repaired.
Click to expand...

I haven't a serial cable to test my fix on the serial port. But here is the mod :
IMG_3911.jpeg

For the SCSI port, I found the simplest solution. Just remove the pin from the SCSI connector. SCSI is still working after this mod.
IMG_3912.jpegIMG_3913.jpeg
 
Kris92

Kris92

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Can someone confirm that the finder report 4Mb with maceffects board 1.6b ?
Mine only report 2Mb. And I found different routings with 74F257 chip within the PCB, boman and retraced schematics. It may be the origin of my problem.
Or a defective BBU.

Before someone ask, J16 jumper is not set.
 
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P

pff000

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Oct 1, 2024
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Kris92 said:
Can someone confirm that the finder report 4Mb with maceffects board 1.6b ?
Mine only report 2Mb. And I found different routings with 74F257 chip within the PCB, boman and retraced schematics. It may be the origin of my problem.
Or a defective BBU.

Before someone ask, J16 jumper is not set.
Click to expand...
I can confirm in my board the finder reports 4Mb. Also maceffects 1.6b
 
Kris92

Kris92

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Kai Robinson said:
Just checking, you don't have the ram jumper set, do you?
Click to expand...
No of course. I tested all the ICs on another board and got the same problem.
I tested with different SIMMs. Curiously, a set of 4x256k SIMMs was recognized (1MB total).
I'm waiting for another BBU next week.
 
Kris92

Kris92

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Just fixed my problem with a new BBU.

BUT : New chip is 344S0603-B and previous was 344S0603-A. So was my 344S0603-A just partially broken (can't access more than 2M) ? Or not compatible with a reloaded board or SE board with jumper ?
I noticed JDW used a 344S0603-A for its YouTube build. But I don't know if this build did recognize 4M RAM ?
 
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Kai Robinson

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The A vs B is merely an erratum fix, it may have just partially died, as the A version can still address 4MB.
 
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Kris92

Kris92

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Does someone know why A19, A20, A21, A22 routing from the CPU to the PDS slot and the BBU use so a long path ? Is it to avoid a timing issue ? Here is an example of A22.
As you can see, the path do a full loop before being routed to the BBU...

Capture d’écran 2026-10-25 à 16.35.11.png
 
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Knife Cult

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This was probably routed before most of the CAD tools were in good shape. It looks like there is a lot of cleanup that could be done now. Even this little section is a mess:

It's a relatively simple design and just moving a few traces around clears up space for further cleanup and refinement.

It is disappointing to me that these reverse engineering projects don't lead to anything new/improved. For example, it seems to me that switching to 72-pin SIMM modules/sockets would be a simple improvement that would free up board space to directly incorporate some other new stuff.
 

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Kris92

Kris92

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Jun 1, 2026
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Knife Cult said:
This was probably routed before most of the CAD tools were in good shape. It looks like there is a lot of cleanup that could be done now. Even this little section is a mess:

It's a relatively simple design and just moving a few traces around clears up space for further cleanup and refinement.

It is disappointing to me that these reverse engineering projects don't lead to anything new/improved. For example, it seems to me that switching to 72-pin SIMM modules/sockets would be a simple improvement that would free up board space to directly incorporate some other new stuff.
Click to expand...
I'm working this way (a bit). I added direct support for both Apple ROMs and 27c010 EPROMS. RC filters can be originals ones or SMD version on the PCB. And I added the frequency divider for better 16F88 support (ADB).
 
JDW

JDW

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@Kai Robinson can correct me if I'm wrong, but I believe the SE Reloaded board layout began during the 2020 COVID lockdowns. The board has been through a few revisions now. I can only say that the SE Reloaded motherboard that I made a video series about continues to work flawlessly to this day.

I suppose we should always appreciate trace-refinements when someone offers to do that work, but seeing the current board functions just as the stock board did, any refinements are probably more along the lines of Steve Jobs trying to make "the unseen look perfect" more than resolving a particular problem or enhancing performance.

In regards to any disappointment expressed over a "cloning" project for not having deviated from the original (and thereby NOT being a clone), I can only suggest that any kind of "SE Motherboard ENHANCED" variants to a new development thread that doesn't try to be a clone of the stock motherboard. For example, something that remains largely an SE, yet isn't. LISA-FGPA isn't a clone of the LISA, but it's an important project that finally got a "LISA" into my hands. Because of that, I believe strongly that non-clone projects are important. But at the same time, I don't believe they really have anything to do with the importance or excellence of cloning products like SE Reloaded.
 
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