And this guy calls himself a journalist? So much for research and fact checking.
Indeed.
And the Square chip is the (Fat) Agnus.
The 8520 are two serial+parallel port chips of which one parallel connections are used for the front Mouse/Joystick ports. Those things are hard to get if you blow one up ...
I have that model as well, bought originally in 1989 in Germany for 4000 Deutschmarks.
With Bridgeboard (8088/8086) and 20Mb Hardcard (HD) in XT Slot which required floppy boot to boot to an AMIGA partition on the PC Harddisk
Initially I had it seperated into two 10Mb partitions: on for DOS 3.2, one for AMIGADOS/Workbench.
I went through some HD's with SCSI controllers for native booting from HD, and it currently no longer holds the bridgeboard (got PC's in the house anyway), but a 800Mb SCSI HD and a SCSI CD-ROM I never got to working (missing the proper mountlist entries).
I should really start that beast up again sometime. It's still functional as far as I know, even if the clock battery is out by now.
