The 5170 AT hard disk controller is limping along now, so I'm getting ready for a 1.15.4 release

Some other interesting bugs were fixed along the way:
the Video component incorrectly assumed that masking a negative number with 0x80000000 would yield 0x80000000 (it actually yields -0x80000000, thank you JavaScript);
the ChipSet component provides a new addCMOSMemory() interface that RAM objects can use to bump the CMOS total to match the actual total;
the CPU properly implements INSW and OUTSW instructions now (kind of important for the AT hard disk controller)

my_modules/pcjs-client/lib/x86seg.js

@@ -123,9 +123,15 @@ X86Seg.loadProt = function loadProt(sel, fSuppress)
          */
         this.cpu.nStepCycles -= 15;
         
+        /*
+         * TODO: Use (direct) Bus memory interfaces instead of (indirect) CPU memory interfaces here?
+         */
         var limit = this.cpu.getWord(offDT + X86.DESC.LIMIT.OFFSET);
         var acc = this.cpu.getWord(offDT + X86.DESC.ACC.OFFSET);
         var base = this.cpu.getWord(offDT + X86.DESC.BASE.OFFSET) | ((acc & X86.DESC.ACC.BASE1623) << 16);
+        
+        Component.assert(this.cpu.getWord(offDT + 0x06) == 0);
+        
         /*
          * For LSL (which uses fSuppress), we must support X86.DESC.ACC.TYPE.SEG as well as TSS and LDT.
          */