[Info-vax] Intel proposal to simplify x86-64

[Johnny Billquist]

On 2023-06-07 19:58, Simon Clubley wrote:
> On 2023-06-07, Johnny Billquist <bqt at softjar.se> wrote:
>>
>> Slightly related, I could argue that RSX (and maybe to some extent VMS)
>> are already slightly down the path of microkernels.
>>
>> In RSX, the file system operations are done in a separate user level
>> process, which is the F11ACP. And networking is done in yet another user
>> level process, the NETACP. Task activation as well as rundown are yet
>> again done by other user level processes (INS and TKTN).
>>
>> This also means that in theory adding support for new file systems is
>> just a question of writing another ACP and off you go. Unfortunately
>> there are a few places where there are some assumptions in the system,
>> making it not that easy to do absolutely everything in another file
>> system. But for normal file accesses, it works just fine. (In RSX, the
>> problem is that task checkpointing is done outside of the ACP, but to
>> the file system.)
>>
>> Which is way more separation than you'll find in any kind of Unix like
>> system. But it's not as far as true microkernels go.
>>
> 
> User mode filesystems are available for a subset of Unix systems however:
> 
> https://en.wikipedia.org/wiki/Filesystem_in_Userspace
> 
> You can also access some USB devices from user mode as well:
> 
> https://libusb.info/
> 
> And finally, you can implement network protocols in user mode using
> the TUN/TAP device drivers.

Fair enough. *These days*, *some* Unix-like systems do allow you to 
implement parts in user space.

Definitely wasn't the case 30 years ago... :-)

   Johnny