Finally finished my SXL2-90 build based on the results from this thread.
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Decided to go all SCSI (AHA-1520B):
ACARD 7722 with HDD firmware swap + custom 50-pin narrow SCSI PCB to terminate the high byte+ Sandisk 8 GB CF + CF-IDE slot bracket
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NEC SCSI CD-ROM
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ZIP 100 SCSI
Yeah, it would have been much easier to just use a SCSI2SD or subsequent clones, but I wanted a system with swap-able CF cards. And my other SXL2-66 system already uses SCSI2SD. Notice how only one CF-IDE slot-bracket is actually connected. The other CF-IDE slot bracket is just a holder for swapping CF cards. Otherwise, the secondary CF card could accidentally get used for another system or lost.
I ran out of slots, so decided to drill out one of the CF-IDE brackets to run the PS/2 mouse port.
Added 3C509B ethernet, serial/parallel, Cirrus Logic GD-5434 video, ES1868 sound w/Dreamblaster X2. Also added a Floppy-Max controller card for the LS-120 superdisk drive. This lets me boot to 1.44 MB and 120 MB floppies directly.
Unfortunately, the CPU location is directly under the HDD caddie. This means I would have to disassemble the whole system to swap the CPU. I decided to leave the 99 cent buck regulator in series with the interposer's linear VRM. If it fails, I can still directly connect the 12 V rail to the interposer. The buck is set to output 6.2 V, the linear is set to output 5.20 V.
The 461 northbridge was running at about 50 C with sustained uptime. This seemed a bit warm to me when compared to other 386 chipsets, thus I added a heatsink. The heatsink stays at under 32 C. Also, the DRAM gets to about 50 C in the centre after sustained uptime (30 minutes). This seems a bit hot for a 386. Not sure if this means anything?
Plan your life wisely, you'll be dead before you know it.