IRIX versions for SGIs can be a pain. The easiest recommendation is as follows For Indigo2 forget 5.3 unless you're running a minimum system. There are many many different versions for specific hardware and they are hard to get a hold of the right one. Doesn't run at all on anything other than IP22 (R4400) on the I2, not POSIX complient so you'll have trouble building your own S/W. For most Indigo2s what you want is IRIX 6.2- fast, POSIX/Y2k complient (when patched) and smallish. It also has 64-bit XFS. You want at least 64 MB. For Indigo2 R10000 you need a special release (th only one for 6.2), IRIX 6.2 with Indigo2 IMPACT 10000 (this release will run on all Indigo2s and Indys, can't remember about Indigo R4ks, but NOT any big system.) Forget about 6.3&6.4, these are HW specific for O2 and Octane/Onyx2/Origins. 6.0 and 6.1 likewise, buggy and only for the R8000. Fast R4400 and R10000 systems probably benefit from IRIX 6.5.x, any version will run on them (I've heard that 6.5.14 and 6.5.22 are the best, I run .22, last version for pre O2/Octane equipment.) .22 seems faster than .17 to me. Disadvantage - somewhat pricey on the "grey market" (bought seperate from a system). You will want more than 128 MB of RAM, though. They will boot from any disk (default is system disk: ID1, CDROM id#3, but they aren't so fussy as Suns. As has been said, SGI decided to be "different" and make the host adapter 0 instead of 7). Mine is perfectly happy with a SCA adapted disk on the sled. Indigo2 might look bad next to an Octane, but in many things it will trash or keep up with O2, so don't knock it yet. Where are these $100 Octanes? I want one! Scott Quinn