[robespierre]

Why won't the Fuel DVD work in the Indigo?  I know I used a Pioneer slot-load DVD-ROM drive to install IRIX on my R4K Indigo.

The R3000 Indigo (IP12) has an older PROM version and doesn't understand optical media. The CDROMs that support it have special firmware (when appropriately jumpered) that pretends to be a hard disk.
The R4000 Indigo (IP20) is more similar to an Indigo2 or Indy in this regard and will work with a wider set of optical devices.

You can refer to the Texas A&M University SGI FAQs for questions like this.
https://www.siliconbunny.com/mirrors/www...index.html

So, from research since I have a DAT drive in my Fuel, I can make a tape to load IRIX from.

Beware, I think the boottape tools weren't supported after 5.3.

IRIX 5.3 would be best and avoid 6.2 or 6.3 which I think was the last release to support the Indigo.

The last release with support for the R3000 Indigo is 5.3 w/ XFS.
The last release with support for the R4000 Indigo is 6.5.22.