INITRD Basics

[GMN]

When using "initrd" to download a file, how is that file accessible in UEFI context?

I was expecting to see a new file system device created, but I find no new devices. For example.

initrd http:/blahblah/disk_image.dsk
kernel http:/blahblah/bootx64.efi /efi/boot/

At this point, UEFI is able to find and execute bootx64.efi (an OS loader), but how do I locate the prior initrd of disk_image.dsk?

I expected to find a UEFI RAMdisk or new file system device created, but I am not seeing this.

Obviously the file disk_image.dsk is in memory somewhere, but how does my OS loader find it? If not via memory address and size, then through what protocol?

Is there a detailed description somewhere of what is actually happening when iPXE pulls images down?