The term 'PDS-slot' covers not one but many possibilities. The SE/30 and the IIsi have a common arangement of their 120-pin female connector on their MLBs, known as an 030 PDS (slot), so what plugs into the one safely also plugs into the other. That, however, is where the cosy arrangement ends. A Processor-Direct Slot is just that, as contemplation of the IIci's adapter, which directly replaces the CPU (if that is removable), makes clear. The cache slot of the IIci (the IIci PDS) is the 'universal' receptacle that DayStar PowerCache and Turbo 040 cards were designed to plug into. The SE/30's and IIsi's PDS is not directly pin-compatible with the IIci's PDS, nor are most of the other Macintosh II (and some members of the LC) series PDSs. Enter The Adapters. Several makers (Apple and DayStar—of course—MicroMac, Radius, and so on) produced adapters for the IIsi, but not all of those were intended for processor-upgrading via a IIci PDS-adapter: some were to provide a NuBus slot, or a NIC connection (straight-through), or whatever. Unless an adapter in your possession has at least one slot clearly marked as 'Processor' or words that can reasonably be thought to imply the like, you risk losing the magic smoke by connecting your PowerCache card to the IIsi PDS, either directly or through an inappropriate adapter.

You can get some idea of the variety of adapters that was needed to suit all the Macs that could profit from the PowerCache card here. If you have no other source, it's worth an email to the eBay seller macmetex to see what he has at the moment.

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