The first Mac I owned was a used SE with a 40 MB HD, the model that could read 1.44 MB and MS-DOS diskettes as well as the 800K diskettes.
When it became old enough to feel slow and short on RAM, I souped it up with an Applied Engineering TransWarp '030 board running at 40 MHz. It was like turning it into a IIfx! More interesting, in retrospect, is what it did for my RAM situation. The SE is natively limited to 4 MB. System 7 had been out long enough that a lot of new apps were too RAM-hungry for a 4 MB box to thrive and make use of multitasking. I stuck with System 6 (in mono-Finder mode) but more and more apps required 7 so that wasn't a good long-term strategy either. The AE TransWarp board had its own separate array of 4 30-pin SIMMS slots, each of which could take up to 4 MB, at least in theory.
In practice, when the board first shipped, Applied Engineering warned me that until they ironed out some bugs and released a patch, I'd be limited to 4 MB. I bought it anyway, AND optimistically shelled out for the full 16 MB, which was more expensive than the accelerator board itself! I'm not sure that's a good comment on my judgment, but I did it.
It took something like 18 months but eventually they sent out an email about getting the update to be able to use the full 16. It wasn't a software patch; I had to remove the accelerator board and mail it to them and they'd alter it physically in some unspecified fashion and mail it back.
It worked! Not only did I have 16 MB of RAM on a Mac SE, I had 16 MB of RAM even under System 6! The largest contiguous chunk of RAM was 4 MB (or lower if I launched enough apps to eat more than 12 MB). That gives some clue as to how they did it. But I had a blisteringly fast little toasterMac with enough RAM to thrive under 6.0.8 (with MultiFinder, finally) and, 7.1.
Some time around 1996, I was trying to clean some corrosion off the pins and somehow managed to damage something and the board never worked again. Discarded it sadly a few years later.
It seems like Applied Engineering went out of business in less than a year after they patched my accelerator to enable the 16 MB of RAM to actually be available. That doesn't bode well for finding one for nostalgic retro-computing. Indeed, I've never seen one advertised on eBay or elsewhere and I never see it discussed in forums online. Whenever I see Applied Engineering and/or TransWarp mentioned, it's always, invariably, the Apple II accelerator that's being discussed.
I sure would like to get my hands on a working AE TW board like that again, and snag an SE. That Mac is the only one I ever owned for which I have neither the original nor a replacement in my little Mac mini-museum.
Anyone here recall this board, have one or remember the ads or see someone else with it?