The 27-inch 5K iMac was introduced in October and got a price cut in May, but it still hasn't been joined by a smaller, cheaper 4K iMac. According to references found in the latest OS X El Capitan developer beta, we may have one coming soon, and it could be using the quad-core Intel Broadwell processors that were introduced earlier this month.

A tipster pointed 9to5Mac toward the relevant text strings. One shows an Apple-made display with a resolution of 4096×2304, and another shows a reference to Broadwell's Iris Pro 6200 GPU. Most outlets, 9to5Mac included, have assumed that this is some kind of 21.5-inch 4K iMac, which makes sense since current iMacs use Iris Pro 5200 GPUs.

That said, if we are looking at a 4K iMac, that resolution would be an odd choice. The 5K iMac has a screen with exactly four times the number of pixels of the non-retina 27-inch iMac—5120×2880 compared to 2560×1440. 2015 Retina MacBook aside, that's how Apple has always added Retina displays to its Macs. By that logic, though, a 4K version of the current 21.5-inch iMac would use a 3840×2160 screen, four times the pixels in the current model's 1080p display. Some kind of 4K iMac is still the best general fit for these specs (and 4096×2304 is still a 16:9 aspect ratio), but the model could include other changes as well.

Also included in the beta are references to four new AMD GPU models, the Radeon R9 M380, M390, M395, and M395X. It's probable that these are just speed-bumped, rebadged older GPUs like the M370X in the 2015 Retina MacBook Pro or the desktop 300-series cards, but, in any case, as mid- to high-end mobile GPUs, these would be a good fit for new 21.5-inch and 27-inch iMacs with discrete GPUs.