My 21.5-inch iMac has been my faithful productivity workhorse for close to six years. And each time that Apple has refreshed this all-in-one (AIO) computer, I have resisted the urge to upgrade.

But the new Apple iMac 21.5-inch with Retina 4K display (mid-2017) might turn out to be my next iMac.

The iMac lineup has been updated with the seventh-generation Kaby Lake processors of up to 4.2GHz and twice the memory from its 2015 predecessors. It is also packed with up to three times more powerful graphics and brighter Retina displays.

The review unit is the top-end model that comes with 3.4GHz quad-core Kaby Lake Intel Core i5 processor, 8GB of system memory, a 1TB Fusion Drive and a Radeon Pro 560 graphics card with 4GB of video memory.

Design wise, the iMac is virtually unchanged from the last refresh in 2015. It retains the same beautiful physical design of its predecessor. It is still an aluminium body with a curved back that tapers to a 5mm-thick edge.

But this also means all its ports are still sited at the back. Having to reach behind to insert an SD card or USB cable is a major inconvenience.

However, instead of Thunderbolt 2 ports, it now features two Thunderbolt 3 or USB-C ports.

The Retina 4K display is rated at 500nits, which is around 43 per cent brighter than the previous generations.

It also comes with support for up to one billion colours for more vivid colours and realistic details.

I connected the iMac to my full high-definition monitor and found the difference in the brightness and details to be quite obvious. Especially so when editing photos.

In terms of speed, Apple claims the 21.5-inch model delivers up to three times faster performance compared with the previous model.

In the Geekbench 4 benchmark tests, the review iMac scored 4,889 and 14,079 points in the single and multi-core Geekbench 4 tests, respectively. In comparison, the 2015 21.5-inch iMac with 4K Retina display scored 4,190 (single-core) and 11,526 (multi-core) points.

In terms of graphics performance, the review iMac scored a whopping 94 frames per second (fps) in the CineBench R15 OpenGL benchmark tests. The 2015 21.5-inch iMac could muster only 47fps.

While the performance boost in the new iMac is a given, I would recommend that buyers increase the system memory to future-proof their purchase. I found the review iMac already using up nearly 7GB of the system memory when I had Mail, Safari, Chrome and Word running at the same time.

Maxing the iMac's system memory to 32GB will cost you an additional $840. But I think it will still be money well-spent.

On the downside, there is no option to increase the capacity of the Fusion Drive for the 21.5-inch iMac. I would have preferred being able to upgrade the Fusion Drive to at least 2TB.

But the 21.5-inch iMac is cheaper now, compared with its 2015 models. Previously, the 2015 21.5-inch iMac with Retina 4K display started at $2,288. Now, it starts from $1,898. Even this review model costs only $2,188.

Trevor Tan

•Verdict: The Apple iMac 21.5-inch with Retina 4K display (mid-2017) might not be much of an upgrade for those using the 2015 model. But if you are using an older iMac, it is time to part with your cash.