No, IDE drives are supported internally on all Ultra model e4s. It's the FAT32 compatible disc formatting that's only supported in EOS 4.7. EOS under 4.7 can still format an internal IDE in the regular EOS file system... but only able to address a maximum of 18Gb of disc (whether it's IDE or SCSI).
EOS 4.7 introduced support for FAT32 formatting, the same disc format used on PCs. It allows addressing of much larger hard drives, beyond the 18Gb limit of the EOS formatting system, and makes swapping Zip disks between an E-mu and a PC much simpler.
Below 4.7, you're limited to 18Gb... even if you put in a much larger IDE hard drive, like a 40Gb, you'll only see 18Gb in the E-mu.
If you are installing an IDE drive yourself, without the E-mu Systems IDE mounting kit, you do need to be aware of one important point about connecting the power to the hard drive internally. In order to "encourage" people to buy the mounting kit from E-mu, they reversed the power connector polarity on the E-mu sampler main board. You have to custom rig a power cable to connect the drive, or it might get fried.
Check out
http://www.peterandrew.com/music/studio/sampler/harddrive.html for instructions about modifying the power cable. Note, while his page is about installing an internal SCSI drive in an Ultra, the instructions are the same for an internal IDE (except that you connect the drive control cable to the IDE connector instead of the SCSI connector on the main board... the drive mounting and power connection are identical).
