You mean this, copied straight from the 5200/6200 Dev Note:
Yes it says the 68040 bus is 32 bits "wde", and that L2 cache is attached to the 603 bus and helps to "optomize" system performance. Typos and omissions aren't exactly foreign to these Dev Notes. Note my previous observation that there are exactly zero references to the system bus speed, only to processor internal clock and the 16MHz of the CS/LC PDS slots. It doesn't mention system RAM speed either.
Did you read previously where I noted that there existed ZERO 603 processors that could run at 1:1 processor:board speed exceeding 66MHz? I linked the 603 UM. It's not that many pages. That alone should be enough of a clue that anything physically external to the 75MHz processor on a 6200 is running at a lower rate, specifically no greater than half of that (which is 37.5, if you're curious).
Or maybe the fact that absolutely no Apple support chips produced in 1995 ran faster than about 50MHz, including Capella? Even if it did, there's the fact that neither the L2 chips or Capella changed with the increase to 100 or 120MHz 603e models. If the faster 603e chips ran their external L2 caches at 100 or 120MHz, why did they use exactly the same L2 cache modules from the 75MHz models? Were they somehow upward compatible with a >25% increase? And why did the faster 603e require a heatsink while Capella, now supposedly also running at 100 or 120MHz, didn't? It's because everything outside of the processor on the new models ran at 40MHz while the 603e ran at a multiple of that (2.5 or 3x) internally. Again, according to the documents from Motorola, there were exactly zero 603 or 603e chips that could exceed a 66MHz bus.
Go boot a 52/62/53/63xx, run TattleTech/Newer Gauge or Clockometer/Speedometer/Metronome/whatever and tell me what speed it has the system bus and L2 caches. I guarantee it's 37.5 on the 75MHz models and 40 on the 100/120MHz models.
Anyway going through my cache of Dev Notes, I don't have one for the 6300, only the 5260 which is basically the same as far as the board is concerned: it runs the 100MHz 603e instead of the 75MHz 603. I don't have any Dev Notes for any machines with the 120MHz 603e or the latest variants with soldered ROM and vacant L2 cache slots. These things don't have the greatest documentation.
I'll concede the CS/LC PDS thing as being a rare perfect storm, if it happens at all; I've never tried it because I have few non-Ethernet LC PDS cards. However, as you noted with the CS Ethernet and IIe card where "Apple says it won't work", I'll assume this is because the CS and LC PDS slot share the same 030 bus and only one can be active at a time. So basically choose one and forget the other (excepting CS modems, which are basically serial pass-through devices not on the 030 bus). Not that there were a ton of options outside of networking anyway.
Doh. Obviously I meant to include that the part I'm referring to starts on page 332.
There are references to other pieces of documentation in Inside Macintosh, technotes, etc. I still imagine it'd be a very tall order to implement a QC accelerator without some source code to reference. I am curious how other vendors that made accelerated cards pulled it off; the fact that they did does imply there's some kind of reference implementation? Question might be whether it required an NDA to see it.
I never upgraded the ram in my 4400, side effect of having too many Macs, but on a Beige G3 a similar problem exists, and the machine only saw half of the ram. I never had a problem with that anomaly though.
I generally remove cards on boot anyway, unless they're used for booting (which USB isn't on something that old). The 2400 (and 3400 on which it's based) is not supposed to have CardBus so there are probably some software routines that don't run properly. I don't consider it a problem big enough to find a solution.
Yeah I guess their marketing team decided that Vimage had brand recognition outside of Japan or something, so Interware used that name on their processor upgrades sold overseas (previously it was specifically applied to their video cards, while their processor upgrades were sold under the Booster name).
I prefer OS 8.6 to 8.1 for a number of reasons, but the main reason to use it here is the FW/USB combo card which doesn't have support on 8.1.