Well, then what is a 3/90?

[dupuy at cs.columbia.edu]

A 3/90 is probably a Sun-4/390, but someone forgot to say "four".  The
complete range of Suns are

Sun-1           Sun-3           Sun-3(x)          Sun-4         Sun-4(c)

 100             50              80                110          *05
 150             60             ~460               150          *10
                 75              470               260           20 (SLC)
Sun-2            110             480               280          *30
                 140                              ^310           40 (IPC)
 50              150                               330          *45
 120             160                              ^360          *50
 160             180            Sun-386i           370           60 (SS1)
 170             260                              ^380           65 (SS1+)
                 280             150               470           70 (SS2)
                                 250              ^480          *75
                                #350 (486i)        490          *85

Notes:
        # never released
        ~ upgrade model with 68030 CPU and 3/160 or 3/260 chassis
        ^ upgrade model with 4300 or 4400 SPARC CPU board (by first digit)
          and 4/110, 3/160. 3/260, 3/280 or 4/280  chassis (by last two digits)
        * not yet released, machine type from <sun4c/cpu.h> in 4.1

By the way, if you're not totally humor-blind (like me) <sun4c/cpu.h> has
a very funny little joke in it.  I really had to kick myself when I
finally got it.

@alex