However, it's possible to upgrade an 800k-drive SE with a Superdrive. To do this you need the drive and three replacement chips for the SE motherboard. Apple used to sell an upgrade kit that included a drive and the chips, and you might still be able to find one from a supplier that specialises in old Mac stuff. See the links page for a list of suppliers. For details on opening up an SE and removing the motherboard, click here.
According to Larry Pina's book, Mac Classic & SE Repair and Upgrade Secrets, the chips you need to swap are these:
original chip replace with 342-0352-A HI ROM 342-0701 HI ROM 342-0353-A LO ROM 342-0702 LO ROM 344-0043-A IWM 344-0062-01 SWM
One visitor to these pages tells me there is an alternative chip set, whose numbers start with 341 rather than 342.
A simple way to upgrade is to get a motherboard from an SE that had a Superdrive and swap it with your SE's board. Then remove the old floppy drive and install a 1.4MB Superdrive. Note that there are two kinds of high-density drive, 'manual insert' and 'auto insert'. You need auto insert, the kind that grabs the disk from you when you put it in the slot. There are suppliers who sometimes have motherboards and drives for sale, or you could advertise on the net in a newsgroup or mailing list - again, see the links page for suppliers and online resources. Alternatively, if you can find a non-working Superdrive SE, you could cannibalise the three chips and drive, assuming that they're not damaged.
The 800K drives have Sony part numbers like MP-F51W-23 (on the bottom), while Superdrives have numbers like MP-F75W-10G. The easiest way to tell them apart is to look at the front where you put the disk in - 800K drives have two tiny lever-type switches, while Superdrives have three switches with cylindrical push-buttons.
When installing a new drive, it's important to position it so that the disk-insert slot in the drive lines up exactly with the one in the SE's case - and there's a lug on the drive cage that engages with the drive to ensure that happens.
Applied Engineering used to make a high-density drive called the AE HD+ (it says "AE PlusDrive" on the box) which works with any Mac. It plugs into the floppy port of a Plus or SE and there's an extension which installs a driver to handle the high-density format for Macs without the necessary chips. If you have the drive but no software for it, download it from The Mac Driver Museum.
Watch out though, because AE made two other external floppy drives for Macintosh and Apple ][ computers - a standard 1.4MB drive and a standard 800k drive. Neither will read or write 1.4MB disks on an SE or Plus not originally equipped to do so.
Another solution is the old "floptical" format drive, if you can still find one. Here's one user's experience:
"I used a genuine 'Iomega Mac Floptical Subsystem' with my old SE. This allowed me to read 1.4MB Mac and DOS disks, and 720k DOS disks. So along with the SE's built-in 800k drive, I was pretty much set for anything.
"Of course, the Floptical's main attraction was its 21MB 'VHD' disks. Nobody is making floptical drives anymore, and the VHD disks (when you can find them) are no bargain. The only vendors of Floptical drives I can think of were Iomega, PLI, and Liberty. I also know that many Apple ][ people like flopticals".
On a Superdrive-capable SE you can connect the drive externally, via the floppy port at the back of the Mac. But you'll need a cable, and it would be nice to have it cased. Here's one user's tip:
"We found that the lead from a very old (and very free) 400k drive fits and works with a Superdrive. You now have a working external disk drive, but what about a case? With major modification to the 400k case you can jam the Superdrive in (be careful not to twist the main chassis as it will affect reliability). To perform the mods use a hacksaw, chisel, whatever turns you on".
If this works with a Superdrive, it might also work with an 800k drive if you have a spare one lying around unused.