Yes, in your and only in your case (A4000).
The original poster has a no-go situation since all IDE adapters for A500 are no-DMA capable, meaning CPU is busted with IDE interrupts in every disk I/O operation. Also, those devices are non-buffered.
You have noticed performance upgrade (SCSI to IDE) because that SCSI is probably 3-4 years older design than IDE drive. While they probably have same rotational speed (7200 rpm), IDE is better due larger cache and like you said more dense platter. However, I doubt about those new drives since Zooro 3 bus troughoutput could became bootleneck.
In either way, those 2 devices sucks big time since solid-state-storage as primary permanent storage media slowly overtakes the ever lasting race. No mechanics - no heat, noise; shock resistant; small weight and overall more reliable.
