Perhaps that issue is mitigated by the G3 upgrade?
The PBX chip, which manages the physical to physical mapping, is on the Motherboard. So, if the Ram is plugged in the normal way, which I think it must be, then the limit must still be 64MB. To repeat. PBX is a 32-entry array of nibbles; one entry per 2MB of physical memory the motherboard can manage. 32 entries x 2MB = 64MB.
Each entry is 3-bits, representing 8 select lines and each select line selects a bank of RAM from 2MB to 16MB. There's 8MB of Motherboard RAM (bank 0); then there's 4MB or 8MB of RAM in bank 1 for the Factory slot (though I think 16MB might be possible). Then bank selects 2..4 pass to the lower RAM card and 5..7 pass to the upper one.
So, you could do 32MB as 2x 16MB banks 2 and 3; while the second 32MB uses 5 and 6. Mac OS might think there's 80MB (8MB Soldered, 8MB factory, 32MB expansions), but 16MB will physically overlap with Factory RAM. e.g. you access the address 0x4000000, but the hardware performs an access to both bank 6 (as intended) and bank 0 (as it wraps around). Because 16MB of memory is aliased, it doesn't really work as intended (and there might be chip timing differences). It might be that the banks aren't allocated as I've described, but the problem will still be as I've described and I guess it's possible you could put a higher load on some RAM or two simultaneously accessed banks will output different data at some point.
It would be wise for you to remove one of the 32MB expansions, taking your PB1400 back down to 48MB. Sell the 32MB and buy a 16MB expansion to take you back up to 64MB. I have 56MB on my PB1400, so I'm OK, very OK - I can run Mac OS 8.1 with VM off and run SoftWindows 3.1 on top of that; and run Turbo C++ 4.5 for Windows usably on top of that too (it worked fine in 32MB on my PM4400/160 in the day, so 56MB is a luxury [he says in a Yorkshire accent]).
Addendum
How is it that Mac OS could think there's 80MB, but really there's only 64MB? The answer is how Mac OS or the ROM measures RAM. 8MB is soldered in, so Bank 0 can be set up immediately. Then all the other banks can be tested by allocating them to the same physical address range: 16MB to 24MB. The Mac finds that select line 1 has 8MB installed (factory RAM). Then it finds individual select lines 2, 3, 5 and 6 all contain 16MB of RAM too, so it adds it all up to 80MB. So it maps them, but it's not real, there's a discrepancy between the PBX mapping and the OS RAM allocation as described above.
surprise # 3. So what i thought was a $120 kick to the crotch was actually a good deal. Now my good 1400c 166 is maxed out.
