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I think I found the beginning of the response. As you can notice on the picture below, Signals E, /AS, /RST and A19-A22 are duplicated on the same row and linked together. All signals from the CPU are routed to column A pins and outputted on column B. Interestingly, signals on column B are...

My question was about the original Apple motherboard too

The problem I'm trying to address is that ADB chip are not easy to find nowadays. And the PIC replacement does not work with all 16F88 (I didn't found any). Same problem with the FDHD ROMs. They are difficult to source. So a direct fit for 27c010 EPROMs seems to me a clean solution. Same thing...

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).

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...

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...

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.

Thank you ! I will dig a bit deeper.

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.

Did you look at cpld source at https://github.com/garrettsworkshop/WarpSE-firmware ? I did a quick scan of the code and it seems to be matching the latest PCB.

I haven't a serial cable to test my fix on the serial port. But here is the mod : For the SCSI port, I found the simplest solution. Just remove the pin from the SCSI connector. SCSI is still working after this mod.

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...

Hello, A long time passed since the last PCB revision. I found 2 errors : • pin12 from 26L32 (C3) is not connected to GND. It may cause some instability on serial ports. • pin 25 on internal SCSI connector (J5) is connected to GND. Normally, it should not be connected to GND to prevent a drama...