I was hoping someone could just make sense of the strange phenomenon I describe below. I use four HDDs each on three PCs. I need to change between HDDs a lot, and I would rather avoid removing and replacing leads, so I bought 4-switch units with the form-factor of a strip such as is normally on the end of a PCI card. There is a LED indicator associated with each switch. After some weeks, the 4 switches lost their independence and so the unit became less useful. So I bought a number more of them but the experience was repeated with each 'set of 4 switches'. I have also bought one at twice the price of the originals - its form-factor resembles a floppy disc drive. So far it has behaved as required/desired, but it is early days. The difference experienced in the three PCs : PC1 - Four spinning-disk HDDs - the 'strip' switch works fine. PC2 - Three SSDs and one spinning-disk HDD - The strip-switch LEDs light up 'randomly'; the more expensive switch has worked up to now. PC3 - Three spinning-disk HDDs and one SSD - The strip-switch LEDs light up 'randomly'. Having figured that the mixture of SSDs and spining-disk HDDs on the same strip-switch spells trouble, I connected the strip-switch to only spinning-disk HDDs and so far it has behaved well. To be able to isolate the SSD, I fitted a molex-power switch between the SSD and the PSU, with (obviously) a molex-to-SATA power adapter to the SSD. The SSD ignored the On/Off setting of the molex-power-switch, and so the PC booted from the SSD irrespective of the molex-power-switch setting. I have tested the switch unit of the molex-power-switch with a digital multimeter which showed low resistance when closed and high resistance when open, so the switch WORKS. 1. It seems that an SSD remains powered, when a spinning-disk HDD would be off. 2. Swtching with both both SSDs and spinning-disk HDDs connected, causes problems EVENTUALLY. Any enlightenment would be welcome.