RE: Where is IBM?

> From: Hans Boldt

Hi Hans!

> Hi Joe! First of all, don't get me wrong - I think the iSeries is a
> great machine. But I have to take issue with some of your comments.

Of course you do <grin>.

> Regarding virtual memory, today, practically all operating systems
> (at least desktop level and above) implement virtual memory
> addressing.
>
> What OS/400 adds to that is the concept of single level store, in
> which the persistent store (hard disks) is basically considered one
> big swap file. Any address in any process can refer to any piece of
> memory anywhere within the (necessarily) large address space.

Thanks for a cogent explanation.  Single store is of course what I'm talking
about when I talk about virtual memory space.  But when the discussion
starts with "Windows supports more memory than the AS/400", the subtleties
are lost.  However, thanks again for this concise description of single
store.

> There's nothing
> really in RPG or COBOL that take advantage of the single level store
> concept!

Well, yes and no.  First, the obvious benefit is that the operating system
automatically handles really large files without you having to do anything
about it.  In desktop operating environments, terabyte files require some
serious manipulation in your application, if for nothing else than because
you have to deal with them as multi-volume files.

Second, and less obvious, is that since they use the large pointers, you
never have to hear about application programs having to be converted to use
"the new 16-bit", or "32-bit" or now "64-bit" architecture.  If Windows
moves to 64-bit pointers, that's a whole lot of application programs that
will need to change.

> What's my point in all this? Single level store is certainly an
> interesting idea. But in my opinion, it's not really that
> significant a factor in the success of the AS/400 and iSeries. And
> because of it's heavy resource requirements, it may have been a
> limiting factor, especially in the days of the S/38. But then who
> knows where we would be today if the S/38 had been designed with a
> more conventional architecture?

<laughing>

Other than stability and object-level security, you mean?  See, you and I
have a different opinion on what makes the midrange successful.  For me,
it's the fact that things are so encapsulated, including access to files and
programs.  The single store memory mechanism is a significant part of that
encapsulation, in my opinion.

But hey, opinions are like - well, everyone's got one, anyway <grin>.

Joe