[Info-vax] New CEO of VMS Software

[Lawrence D'Oliveiro]

On Sat, 6 Jan 2024 15:30 +0000 (GMT Standard Time), John Dallman wrote:

> It can't be made fully 64-bit without breaking source-level
> compatibility with customer code.
> ...
> Obviously, DEC needed a 64-bit VMS. They also needed it /soon/, so they
> added 64-bit versions of the APIs that most needed to deal with lots of
> memory. Quite a lot of APIs that took pointers to user memory carried on
> taking 32-bit pointers, and thus could only deal with data in the bottom
> 2GB of a process address space. 
> 
> They probably intended to add 64-bit versions of all the other APIs, but
> this never happened, for reasons that probably included some of:
> 
> * Lack of budget: DEC was never as successful in the 1990s as it 
>   had been in the 1980s.

Yes, but remember, at the same time, they were able to bring out their own 
Unix OS for the same hardware, and make it fully 64-bit from the get-go.

Look at how the Linux kernel does it, on platforms (e.g. x86) where 32-bit 
code still matters: it is able to be fully 64-bit internally, yet offer 
both 32-bit and 64-bit APIs to userland.

By about 1996, there were 4 OSes that you might say were in common use on 
Alpha: DEC Unix, OpenVMS, Windows NT, and Linux. Two of them (Unix and 
Linux) were fully 64-bit; one (OpenVMS) was a hybrid of 32- and 64-bit 
code; and Windows NT was 32-bit only.