[Info-vax] openvms and xterm

[John Dallman]

In article <MPG.40a3022658647d279896e1 at news.zx.net.nz>,
david+usenet at zx.net.nz (David Goodwin) wrote:

> In article <v16nsc$1gbho$2 at dont-email.me>, ldo at nz.invalid says...

> > No, ARM and POWER and MIPS are all still very much here and 
> > continuing to be made and sold. And like I said, even with the 
> > massive popularity of ARM, Microsoft still can't get Windows 
> > running properly on it.

Oh, it runs, reasonably well. Microsoft are a bit confused about what
they should be doing with it, but they are gradually working towards it
being an all-purpose platform. Qualcomm seem to have convinced them at
one point that the hardware should be all be Qualcomm proprietor
platforms, but they seem to be climbing out of that hole now.

> Been a long time since I've seen PowerPC or MIPS PCs on store 
> shelves...
> 
> The PowerPC port ended when IBM stopped including ARC-compatible 
> firmware on new machines. The MIPS port ended when you could no 
> longer buy MIPS workstations with ARC firmware. Compatible hardware 
> was discontinued so the ports were discontinued.
> 
> Microsoft could have taken on supporting these platforms with 
> whatever random firmware they have like Linux does. But Microsoft 
> is selling a product here - if the number of sales to people who 
> want to run Windows rather than AIX on their brand new RS/6000 
> doesn't cover the costs its not worth doing.
> 
> That doesn't mean it can't be done or that Windows NT isn't 
> portable. It just means it doesn't make business sense to do it. 

My employer had an explanation for Windows NT platforms, back in the late
1990s:

  x86 is the default. If you don't have good reason for wanting 
  a different platform, you want x86. 
  
We supported it then, and still do to this day. 

  Alpha is the fastest. That's a good reason. 
  
We supported it until about 2000, by which time it was no longer the
fastest and was being dropped by Compaq. 

  PowerPC is what you want if you're very keen on IBM and believe 
  their claims of integration with AIX and MacOS.
  
We never supported this. We looked at it, but there was no significant
customer demand and the hardware was very expensive. 

  MIPS was used to develop Windows NT but doesn't have a reason as
  compelling as PowerPC. 
  
We worked on a port. We hit the same problem as we had on MIPS/Ultrix and
Irix, which seems to go back to MIPS' original code generator from
RISC/os (not to be confused with RISC OS). We had to get it fixed
separately on all three platforms. 

The compiler assumed that any C struct passed by value would have uniform
alignment requirements for all of its members. It simply pushed the
members onto the stack, ignoring any padding in the struct. It did not
pop the members into a buffer in the called function, it just used the
copy on the stack as the passed variable. If omitting padding had caused
any members to become misaligned, you got a SIGBUS as soon as you
accessed them. 

About the time we'd got MS to fix the Windows version of this bug, it
became clear the Pentium Pro had destroyed any performance advantage MIPS
held over x86, and the customer abandoned MIPS and decided to build x86
workstations instead. They went bust a year or so later. 

> Same goes for ARM - Windows runs on ARM devices built to run 
> Windows. For business reasons Microsoft doesn't spend money porting 
> Windows to any random ARM device thats designed and sold for some 
> other purpose.

There is also a distinct shortage of ARM SoCs with high performance-per-
thread suitable for development machines. The good ones are made by Apple,
and Microsoft don't seem to want to support them. 

> > The fact that every single one of those ports ran in into trouble 
> > clearly demonstrates that that ?portability? was more of a PR 
> > claim than practical.
> 
> None of them ran into technical problems. The ports exist and they 
> work. I have PowerPC and Alpha hardware here running Windows NT and 
> it works just fine. Only reason I don't have a MIPS is because 
> they're extremely rare. The operating system itself is 
> indistinguishable from the regular x86 version and all the included 
> utilities work just the same. The operating system is portable and 
> its a bit absurd to try and claim otherwise.

Yup. I've used it on x86, x86-64, Alpha, Itanium and Aarch64. The
problems have been with hardware performance/availability and marketing,
not the OS. 

Also, something Dave Cutler did while at Microsoft was very good for
everyone. When Intel had to admit that Itanium was not working out and
they needed to do a 64-bit x86, they initially wanted to use a different
instruction encoding from AMD, so that binaries could not be compatible
with both Intel and AMD. Dave Cutler's response was "You can do that if
you want, but you won't have Windows for it." Intel had to climb down. 

> Would be interested to see Linux using fat32 as the root 
> filesystem. Last I checked it wasn't possible due to missing 
> features in that filesystem.

I've done something similar to that on Android, on devices that didn't
have enough built-in storage so I had to use large micro-SD cards for
test data. You really do not want to see what FAT32 does to the
performance of directory seeks in directories with lots of files. 

John