Trying to boot NetBSD on '97 Pentium I @ 200 MHz

Hello everyone,

I've found a '97 Pentium I @ 200 MHz machine sitting on top of the 
dumpster and I decided to give it a second chance. The HDD is gone, so 
the PC is diskless at the moment as I am waiting for an IDE to SD card 
adapter to arrive. I want to install an up-to-date OS on it, and I am 
trying out live distributions. The computer cannot boot from USB 
natively, but it can using the Plop boot utility. It can boot from a CD 
without any problems. I have tested the memory, and it's OK. I have 
managed to boot and successfully run the FreeDOS live CD. Let's move on 
to NetBSD.

I have created a NetBSD CD (from NetBSD-10.1-i386.iso) and I have tried 
to boot from it. During the boot, NetBSD displays only the following:

NetBSD/x86 cd9660 Primary Bootstrap

... and everything stops there. Not a single character more. The cursor 
is still blinking.

Later, I burned NetBSD-10.1-i386-install.img to USB and used the Plop 
utility to force the boot from USB. That part worked. Now I got the 
following displayed:

NetBSD MBR boot

NetBSD/x86 ffsv1 Primary Bootstrap

... and then everything stops, just like with the CD. The same happened 
with NetBSD versions 9.4 and 8.3.

I am not sure what could be causing the problem here. Could it be the 
fact that the PC has no disk at all? Is there a way to make the boot 
procedure more verbose to see what happens when stage 1 tries to run 
stage 2, or if stage 2 gets stuck somewhere?

Thanks for your suggestions!