[selowitch]

The optical drive on my iMac (Intel C2D, October 2006) works only some of the time. I was thinking it might be a good idea to replace the optical drive with a smallish solid-state drive that would contain the System/boot software (SL) only, so I can boot quickly and quietly from that but continue to use the SATA drive for my apps and data. Is this doable or advisable?

[P]

There is a problem with that: The optical drive has a UATA connection in that model. All SSDs I know of use SATA. Converters exist, but UATA will limit performance significantly. One way around this would be to switch the connections, so you use a the SATA from the HD to the SSD and then use a converter from UATA to the existing HD, but it's not straightforward. Add to this the fact that the white Intel iMacs are very tricky to upgrade, and I'd just save the money and put it towards a replacement.

[mduell]

I say go for it. You'll probably want an adapter from the optical drive ATA connector to SATA, then you can use any SATA SSD.

Originally Posted by P 

There is a problem with that: The optical drive has a UATA connection in that model. All SSDs I know of use SATA. Converters exist, but UATA will limit performance significantly. One way around this would be to switch the connections, so you use a the SATA from the HD to the SSD and then use a converter from UATA to the existing HD, but it's not straightforward. Add to this the fact that the white Intel iMacs are very tricky to upgrade, and I'd just save the money and put it towards a replacement.

ATA will limit the speed of bulk transfers compared to SATA, but that's not what most people are after SSDs for. The difference you notice with an SSD is when you're getting 40MBps instead of 1MBps not 200MBps instead of 80MBps.

[P]

The point about SSDs is latency, not bandwidth - I'm well aware - but the converter adds some latency as well. Add in the fact that the replacement is hard even by iMac standards (this is the guide for the 20" model - the OP didn't mention which size he has), the iMac is 4 years old already, SSDs are still evolving quickly and OS X still doesn't have TRIM support, and it just doesn't make long term sense. I'd probably buy a new computer, or just buy an USB DVD (the one Apple sells for the MBA works with other Macs as well, but any USB DVD will work) and ignore the internal optical.

[Waragainstsleep]

If you're going to use an SSD on the ATA bus, I certainly wouldn't worry about TRIM. I saw a fascinating test of SSD performance degradation using the original MacBook Air which determined that TRIM was completely unnecessary for those machines. I imagine it might make a difference with a faster setup, those Air SSDs were not speed demons by any stretch. The testers were really amazed it didn't lose performance at all.

Also, you generally want to run apps from your boot drive IMO. Especially if its faster. Apps are the worst culprits when it comes to needing to load many many small files from various places on a disk.

You might consider putting a large (S)ATA drive on the optical drive bus with an adaptor for all your files, then either an SSD or maybe one of those Seagate Momentus XT hybrids on the SATA bus to boot from. It might be ever so slightly noisier than an SSD but it will probably be just as fast on that bus and give you more GB for less cash.

[selowitch]

Originally Posted by P 

the OP didn't mention which size he has)

You're right; it's a 20" display.