I have a TiVo Series 3 HD (TCD652160) whose hard drive died a horrible grinding death. Unable to use MFSLive to backup/restore to another hard drive (seemingly infinite read errors on the drive).
Enter InstantCake (yay!). I bought a 1TB WD "red" SATA drive and plugged it in to my SATA-to-USB interface adapter on my iMac. I downloaded the InstantCake ISO for my TiVo (it won't let me post a link but go to dvrupgrade dot com) and then in Fusion created a new VM guest and pointed to the ISO as the boot device.
New virtual machine booted fine, but it became apparent to me I had no idea how to tell it what the CD-ROM device was. There's no apparent mount point for /.
Short version...use the command "dmesg | grep CD" and it will spit out the device that the CD-ROM (or the ISO image) is mounted on, in my case it was hdc--so that also told me that I need to specify it as a PATA device.
Then, in Fusion, logically "connect" the SATA drive to the guest VM. That will result in some console messages that will make it obvious which device the SATA disk is appearing on (in my case it was sda). This will be a SATA device for InstantCake.
Then, in the InstantCake installer (which you either cancelled out of after boot with Ctrl-C, or you let it fail to a # prompt; you can restart it with the command PTVbake3), I told it my CD-ROM was a PATA device on hdc, and my SATA drive was a SATA device on sda.
The installer worked perfectly after that.