grub boot to usb on old non usb boot hardware?

[Xamindar]

I have an old machine that I'm pretty sure has only usb 1.1 and it will not allow booting directly to a usb stick. The machine already has gentoo running on it on the hard drive with grub. Is there a way to have grub come up like normal from the internal hdd and provide a selection to forward booting to a usb flash drive?

[cyrillic]

As far as I know, since grub uses the BIOS to access the drives, grub can only boot from devices that the BIOS can boot from.