With the Apple Silicon Macs, Apple has removed the ability to use an external graphics card, at least for now. But on Intel Macs, these eGPUs work perfectly and in some cases bring a gain that is sometimes very significant. Which case and which card to choose? What performance to expect? Is it a good cost-benefit ratio? Explanations in detail.
Before going any further, we must understand one thing: an external graphics card, in the broad sense of the term, is not something new. Thirty years ago, Radius sold an external SCSI graphics card (the PowerView), which could also be emulated with a RaSCSI. Later, Village Tronic offered the VTBook and IXMicro the Road Rocket, two CardBus graphics cards (the fast version of the PC Card). And from 2006, with the integration of the ExpressCard connector in certain MacBook Pros, external GPU solutions arrived on the market: Village Tronic (again) developed the ViDock, a box capable of accepting a standard graphics card.
But in any case, a problem arose: the link between the graphics card and the system was quite slow. The CardBus offered the bandwidth of the PCI (133 MB/s) when the AGP became common (533 MB/s in AGP 2x) and the ExpressCard a PCI-Express line (250 MB/s) when the graphics cards expected it sixteen (4 GB/s).