@FiLiS @lw so without really knowing what I'm doing I grepped for 'BIOS drive.+: is' and 'Can not get information' and found bd_int13probe()

https://cgit.freebsd.org/src/tree/stand/i386/libi386/biosdisk.c#n604

/*
* Try to detect a device supported by the legacy int13 BIOS
*/
static bool
bd_int13probe(bdinfo_t *bd)
{

which is called from bd_init()

https://cgit.freebsd.org/src/tree/stand/i386/libi386/biosdisk.c#n336

which does for(.., PTOV(BIOS_NUMDRIVES))

which is 0x475 which appears to be a Magic Number pointing into the BIOS memory space which I guess returns more Magic Numbers from the BIOS already.

AFAICT the bd_int13probe() trucks along until it find a device# that doesn't return a response and then stops.

So device 36 appears to be listed in the PTOV(BIOS_NUMDRIVES) data, but on querying, doesn't have the info that the loader expects https://cgit.freebsd.org/src/tree/stand/i386/libi386/biosdisk.c#n661 so we return false to bd_init() and stop.

Rummaging around there the number of enumerable drives appears to be between 0x80 -> 0xff so 128 drives total, but who knows.

Also, I don't know what character it would try for 0xa7 (base of 0x80 + 37) in bd_init(), it's not even printable ASCII...

Toomas or Warner probably knows what actually happens here.