The NEC Slot-in PC has an SSD storage medium which is faster than the HDD storage medium found on most personal computers of this age and type. Solid State Drives (SSD) store information in transistors on a circuit board rather than on optical or magnetic media. This has the advantage of being much faster than a traditional HDD drive.
This desktop computer's storage speed (SSD) is actually the best storage speed amongst all few processor core PCs that were released around the same time as the Slot-in PC.
Amongst similar types of desktop computer the worst storage speed is HDD.