Well, that stinkx.

[Doug Sutherland]

This shows exactly what is included in the slackware 11 speakup.s kernel
http://gulus.usherbrooke.ca/pub/distro/slackware/slackware-11.0/kernels/speakup.s/config

CONFIG_IDE=y
CONFIG_BLK_DEV_IDE=y
CONFIG_BLK_DEV_IDEDISK=y
CONFIG_BLK_DEV_IDECS=m
CONFIG_BLK_DEV_DELKIN=m
CONFIG_BLK_DEV_IDECD=y
CONFIG_BLK_DEV_IDEFLOPPY=y

Further down you see it includes SCSI basically for SATA support.
The changelog for slackware 11 states
bootdisks/speakup.s:  Added SATA support.
kernels/speakup.s/*:  Added SATA support.

It appears to support IDE. And you said it installed yes?
It must have IDE support or it wouldn't have worked at all.

I started using slackware at version 7 and and I love it.

  -- Doug