Once again, there's talk that Apple may be considering ARM-based Macs.

This isn't a new idea, but it makes increasing sense.

Apple already has processor design capability (in part through its 2008 acquisition of PA Semi, which was founded by the lead designer of the StrongARM processor although he left a year after the acquisition) and iOS has a lot in common with OS X (indeed, Apple originally called the iPhone's system software OS X).

Announcing Bob Mansfield's new role - senior vice president, technologies - Apple officials stated that his group "combines all of Apple’s wireless teams across the company in one organization, fostering innovation in this area at an even higher level. This organization will also include the semiconductor teams, who have ambitious plans for the future."

You can't get much more ambitious than moving all Apple's hardware onto in-house processors.

We've already seen Apple manage two Mac hardware transitions remarkably successfully: from 680x0 to PowerPC, and PowerPC to x86. A key part of that success was the provision of mechanisms to keep old software working during the transition period.

But 'rusted on' Mac users have received relatively little attention in recent years, with Apple preferring to attend to the much greater number of newcomers, especially around the iPhone and iPad. So I have a nagging feeling that any ARM-based 'Mac' won't provide that same degree of backward compatibility, and instead will be more like an giant iPad with a keyboard and trackpad than what we currently think of as a Mac. Never mind Think Different, Think Launchpad.

For once, I'd be happy to be proved wrong.

Well, the rumours were correct: the new iMac does lack an optical drive. I still don't feel ready to do without one, but I know people that are.

Photo: Apple

I've heard some criticism of the new design along the lines of "what's the point of making a desktop even slimmer that the iMac was already?", but it seems to me that's missing the point. I've only seen pictures at this stage, but the industrial design seems to keep the good parts of the iMac look (which other companies have tried and failed to emulate) while picking up on current trends such as the elimination of bezels and thinness. Sure, the picture isn't edge to edge, but the removal of the aluminium frame around the black border is an improvement. But I would concede that this does seem to be a case of Apple following rather than setting trends.

Fusion Drive is an interesting idea, but details still seem sketchy. As far as I can see, the OS treats the hard drive and the flash drive as a single volume, with the most frequently used files kept on flash and the rest on the rotating media.

Combining the two drives rather than using flash as a cache maximises the available storage, but does assume that flash is at least as reliable as magnetic storage. I can't say I've heard complaints about reliability from those who have replaced or augmented their hard drive with flash, so maybe the fears being expressed in some quarters are ill-founded.

What might seem to be a problem for some is that Fusion Drive only allows the creation of two partitions on the hard drive. Only one works in conjunction with flash storage, which makes sense. The problem is if you need a Windows partition (created via Boot Camp) and you also prefer to keep certain items (perhaps the user folder or the iTunes library) on a separate volume.

This could be Apple's way of saying 'you don't really want to do that.' I used to be an advocate of drive partitioning, but in recent years I've found it more convenient to stick with one volume per drive (leaving aside the recovery partition). Even if you have to reinstall the OS from scratch - and that's very unusual - Time Machine makes it easy to recover everything else.

About the only situation I can think of where multiple partitions are necessary is if you need to boot from more than one version of the OS in order to run obsolete software, and you want to isolate the two versions as much as possible without going to the length of a separate drive. But since the new iMacs are highly unlikely to work with anything prior to Mountain Lion, that's not really a consideration here.

I like the idea of 8GB of RAM as the minimum as insufficient RAM appears to be one of the major causes of performance issues, but I'm not very happy with the way the 21.5in model is not upgradable in this regard and is instead another of Apple's 'decide what you need at the time of purchase as that's what you'll be stuck with' models. At least the 27in model has user-upgradable RAM.

So when all's said and done, there's not enough in the new iMac to make me rush to order one, but if I was forced to replace my mid-2007 iMac I think I'd be pleased with this year's version even if I did need to buy an external DVD burner.

The announcement of the iPad mini on October 23 seems almost certain now that we know Apple is holding a media event on that day.

But there are also rumours that new Macs will be announced on the same day, specifically a Retina version of the 13in MacBook Pro plus updates to the iMac and Mac mini lines - though details are much sketchier than those concerning the iPad mini.

One suggestion is that the optical drive may be absent from the 'late 2012' iMac and Mac mini. Apple's certainly moving in that direction, and it wouldn't surprise me if it comes to pass.

I'm not quite ready to do without a writable optical disc, so I'd hope Apple increases the number of open USB ports on the iMac to compensate. There are practical alternatives for most uses, but DVD is still one of the best ways of distributing home videos to family members that don't live online.

Thumb drives are cheap enough to use as DVD replacements when sending files by snail mail, and they don't need such careful packaging.

Want to watch a video on your reasonably new flat-screen TV? If you can't plug your computer into it or stream the video via the LAN, how about using a thumb drive?

Archiving? Hard disks are cheaper per gigabyte than blank DVDs, and (depending who you listen to) probably have similar shelf lives.

Ripping CDs? That's probably another deal-breaker. But it's a task you can do on just about any computer, and it's going to be several years before I discard the last of my optical drive equipped systems.

So I think we're now at a similar stage with optical storage as we were with floppies when Apple abruptly dropped them with the early iMac. You can buy an external drive if you think you need it (and get change from $40), but there's a good chance that you don't really need it.

That reminds me: I really should go through that box of floppies before my PowerBook 520c finally gives up the ghost. But then if I haven't needed any of the files in around 10 years, I probably never will.

PS: I'm 'on assignment' next week, so there may not be a post next Thursday.

I review a couple of printers or all-in-ones for APC magazine each month, and these days most of them feature network interfaces. Given that title's focus, I test the models with a Windows PC but sometimes have reason to connect them to a Mac.

Something I like about Lion and Mountain Lion is that in most cases I can hold down the + button (add a device) in the Print & Scan system preference and a list of new "nearby printers" appears.

When I select the required device, the OS checks for the presence of the relevant driver, offers to download it if necessary, and then sets everything up. It's simple, painless, and fairly quick. Perhaps not as simple as using an iPhone or iPad with a printer that supports AirPrint, but still pretty good.

In fact, short of a 'universal driver' approach like AirPrint, it's close to perfect - especially for the growing number of MacBook owners that can't use the CDs that accompany most printers.

So, which OS X feature makes you smile?

PS: Soon after last week's post about the OS X 10.7.5 'slow Time Machine' issue, Apple released the 10.7.5 Supplemental Update to address the problem.

The 10.7.5 update was supposed to "improve the stability, compatibility and security of your Mac" according to Apple. Frankly, I didn't notice any difference, but then I don't use any of the features that were specifically addressed, and Gatekeeper defaulted to its most permissive setting.

But some people have been bitten by a bug that dramatically slows Time Machine backups, though it seems the root cause is in Spotlight as the affected systems reportedly have unusually lengthy reindexing processes underway when slow backups are observed.

While only a minority of users have been affected, there are more complaints than you'd expect if the problem was limited to systems that had suffered minor file corruption. (I'm still amazed by the number of problems that can be fixed by trashing the relevant preferences file.) And there doesn't seem to be any pattern as far as hardware or installed applications are concerned.

There are reports that this is a 'known problem' at Apple and that work is underway on a fix. Meanwhile, various workaround have been proposed (eg, disabling Spotlight), but they don't seem to work for everyone - and in any case, you might need Spotlight.

If you'd like to see some of the discussions, try this thread at Apple Support Communities where there are 449 replies as of this writing, and it's been viewed more than 38,000 times - and it's not the only thread on the topic.

For those that are affected, here's hoping the fix appears sooner rather than later.