Hi, I'm speaking under correction but I think CF cards do support three types of interface modes.
One of them is True-IDE mode. CF-USB card readers likely use memory mapped mode or sonething else.
I thus think that USB removable media support in the host OS is a limiting factor.
Or in other words, the CF card reader might behave more like an USB pen drive under Windows, macOS etc.

Jo22 wrote on 2025-01-26, 14:49:

Hi, I'm speaking under correction but I think CF cards do support three types of interface modes. One of them is True-IDE mode. […]
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Hi, I'm speaking under correction but I think CF cards do support three types of interface modes.
One of them is True-IDE mode. CF-USB card readers likely use memory mapped mode or sonething else.
I thus think that USB removable media support in the host OS is a limiting factor.
Or in other words, the CF card reader might behave more like an USB pen drive under Windows, macOS etc.

They appear as removal drives which I believe are different from your normal thumb drive.

They will always show even if there's no media inserted, once there is media it will mount and work. And you can then eject which will unmount. But the drive letter will still be taken up. It also shows as two drives separate drives so CF and SD can be mounted at the same time.

This is the same behavior as those external 13-in-1 USB card readers. I'm pretty sure the guts are the same. This is also how other other drive bay media card readers functioned as well. This just also includes a floppy drive in the same slot.

Card readers and thumb drives both use the exact same USB Mass Storage command set (based on SCSI), the same goes for HDDs and optical drives. The only typical difference is card readers will support more than one LUN (logical unit) to support the different interfaces. They're not the only devices that do this, some devices will have an extra LUN mapped to read-only flash storage that holds a PDF manual and/or drivers.

weedeewee wrote on 2025-01-24, 19:29:

I wasn't planning on opening it.

But you did, thanks. So it is a direct drive, just more compact, but the rear side of the drive looks almost like any other standard 3.5". Still PITA to service but at least no flimsy belt to replace.