The mysterious mezzanine
Soon after the iMac shipped, enterprising geeks took theirs apart to find out what that plate below the port array was hiding, and were surprised to find that on the underside of the logic board there was a connecter labeled "Mezzanine" that Apple hadn't trumpeted in its promo materials or spec sheets.
The slot turned out to be a proprietary PCI connector — the iMac's Motorola XPC106 bridge chip (aka "Grackle") supports PCI. Its usage by Apple was, to my knowledge, never officially confirmed, but the word on the street is that Apple techs used it to test, monitor, and diagnose the logic board and other system functions.
This slot has absolutely nothing to do with Nicholson Baker's novel (click to enlarge)
A PCI slot in an otherwise expansion-hobbled iMac begged for third-party devices to be plugged into it — but both the cramped location of the slot and its access difficulty for the average user kept the upgrade aftermarket small.
That said, the now-defunct Formac* made a TV tuner–SCSI adapter mashup called the iProTVRAID that fit into the slot. Another now-defunct outfit, Micro Conversions, was said to have announced a mezzanine slot version of its Game Wizard 3DFX VooDoo graphics card, though I've been unable to find out if that card ever shipped.
Nestled next to the mezzanine slot on the bottom of the logic board, by the way, lived the 56Kbps modem I mentioned earlier, powered by a Rockwell L2800-38 and R6764-62 chip pairing.
When stripped of the daughter card and its cage, plus the modem, the Bondi Blue iMac's logicboard is a clean design with no "whoops" do-over traces — at least none that I could spot.
The top of the Bondi Blue iMac's logic board, with the ATI Rage Pro to the left of center (click to enlarge)
Next page: Spinning stuff and nifty speakers
You so nearly got through without your inner fanboi escaping but fluffed it at the end:
"I'm surrounded by the guts of the personal computer that saved Apple, arguably jump-started the internet age, helped kill off the floppy, and brought translucency to everything from George Foreman grills to Rowenta Surfline steam irons."
Jump-started the internet age? My arse. I'd love to see any accurate statistics you may have for the number of people who first experienced the internet or first had the internet at home on an iMac. I'd be prepared to make a healthy wager that the true figure is vanishingly small.
Helped kill off the floppy I can't really sit still for either. Yes it helped but so did about a billion other factors. Claiming the iMac was significant is like trying to take credit for keeping the worlds trees alive because *I* produce CO2. The iMac is way down the list behind CD-R, CD-RW, freefalling drive prices, USB memory sticks, software bloat etc.
You probably deliberately left out the 'i'. We're into our second decade of marketing wonks insisting that anything can be cool if you put an 'i' in front of it. Shoot them, shoot them all.
Translucent everything - oh yes, that's thanks to the iMac for sure which is a marmite thing in itself but you should have highlighted the bigger truth I'd credit the iMac with. It started a revolution in design. We see attempts at aesthetically pleasing design in the most mundane of items these days from cheap radios to phones to, well, you name it. Nothing in a poorly designed or plain beige box stands a prayer. Much as I dislike Apple the iMac deserves a beer for that so here's one.
@Christian Berger re: 56k
It's all comparative.
If you had moved up from 1200/75b/s, through V.22bis, V.32 and V.32bis, then V.90 was fast.
If you were using it for commercial use, then it was almost certainly the upload speed that was your issue, as it was asymmetric and the upload channel was a fraction of the download speed. IIRC, if you did V.90 modem to V.90 modem directly, you could only get 33.6kb/s anyway. You needed something like a DS0 setup, which could directly inject digital signals into the phone system, to give you the 56k download speed to end-users.
Most home users mostly downloaded data, so this was not a big issue.
Don't compare your 20Mb/s ADSL line, or even channel-bonded ISDN with what home users had available at the time, because ISDN was far too expensive for home users to consider, even the 'reduced-cost' Home Highway that BT tried to sell.
I wan my whole household (several computers with thin-wire Ethernet, and then wireless as it became available - we're a techie household) on a dial-on-demand 56K modem for several years, until BT got round to upgrading our exchange to ADSL.
The best-selling computer of all time is the Commodore 64 - by a significant amount.
There's a tendency amongst both Apple execs and fans to re-write history in their favour - Commodore had the best-selling computer ever with the 64, and the first colour DTP machine with the Amiga.