I spent some time fixing the latter because browsers have started warning that synchronous XMLHttpRequest calls on the "main thread" (as Firefox calls it) are deprecated. Since the days of such calls seems to be numbered, I decided to act sooner rather than later. All PCjs XMLHttpRequests go through a single library function (weblib.loadResource), which accepts an fAsync parameter, and the only code that is still allowed to pass false for that parameter are "emergency" shutdown requests (which I believe browsers must still allow).
What this means is that XDF disk images formatted as 80-track 23-sector-per-track images will work with XDF code that honors that format; however, I've not yet been able to test with "real" XDF disk images (ie, disk images created with DiskDump using the experimental --xdf flag). "Real" XDF disk images almost certainly need more work (eg, setting all the sector IDs properly), but the groundwork has been laid.
However, performance will suffer until I can implement RTC interrupts;
also, there may be a problem exposed by the BIOS memory test following a soft reset
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)
