Microsoft's 64 bit transition was more awkward with more compatibility breaks, compared to Apple. Microsoft sold separate Windows 32 bit and 64 bit versions, u

Microsoft's 64 bit transition was more awkward with more compatibility breaks, compared to Apple. Microsoft sold separate Windows 32 bit and 64 bit versions, under different SKUs. The 64 bit version broke compatibility with 32 bit drivers, but not all software would work on 32 bit, so it was important to know which version you had. Many computers advertised as 64 bit were sold with 32 bit Windows, so it was possible to download an incompatible app version. It was a confusing time. Apple had only one SKU. Applications had 32 bit and 64 bit versions in the same binary, so there was only one version to download. The kernel supported 64 bit addressing and 32 bit drivers, so there was no hardware compatibility break. It was invisible to users.