Trying to use this old DT375

I've acquired a few re-branded DT375s. They have pxa255A0c400
processors and they run WinCE 4.2. I want to run netbsd on them.

I've tried using hpcboot, If I try to use the 'serial console' option,
hpcboot will stop after posting "BaudRate 19200, ByteSize 0x8, Parity
0, StopBits 0" on the hpcboot console window.
When I turn the serial console option off, I more or less get the
following regardless of which system I choose.

BOOT START
[progress] 0
[progress] 1
ARM architecture.
MemoryManager: LockPages
FileManager: FAT
hpcboot build number: 14
HP Jornada 820 (cpu=0x0c104000 machine=0x02c20301)
[progress] 2
[0] 0xc0000000 size 0x08000000
[1] 0xc8000000 size 0x08000000
[2] 0xd0000000 size 0x08000000
[3] 0xd8000000 size 0x08000000
_WIN32_WCE = 211
GetVersionEx
Windows CE 4.20
GetSystemInfo:
wProcessorArchitecture      0x5
wProcessorLevel             0x4
wProcessorRevision          0x6
dwPageSize                  0x1000