Re: Intel releases 64bit Xeon

From: Dan Foster (usenet_at_evilphb.org)
Date: 03/04/04 

Date: Thu, 4 Mar 2004 06:31:24 +0000 (UTC)

In article <4046C790.253C5463@istop.com>, JF Mezei
<jfmezei.spamnot@istop.com> wrote:
> Bill Todd wrote:
>> > Note that the 370 architecture doesn't have a bright future since IBM
>> > is porting MVS over to POWER. (or has that been cancelled ?)
>>
>> Nobody's talking about the 370 architecture, JF.
>
> Isn't that what the p390 systems are ????? I realise that since the
> 370s, IBM has managed to go to 31 bit adressing (from 24), but isn't it
> the same assembler instructions with a few additions ??

There are three addressing modes (due to historical growth) for current
mainframe processors:

24 bit, 31 bit, *and* the current 64 bit.

The zSeries systems are based on a 64 bit architecture that is a superset
of ESA/390. Perhaps this is the port you were thinking of? If so, it was
completed a while ago.

The zSeries 990 contains MCMs (multi-chip modules, similar to POWER4), LPAR
support, high speed interconnectivity, and a lot of other stuff you'd
expect with high end hardware.

I'm not clear on the exact relationship between POWER and the mainframe
CPUs but it seems that there is a fair amount of common stuff between
POWER4 and the current mainframe CPUs.

It may be partly due to the in-house reorganization IBM did a few years ago
where they ordered their engineers from various teams to collaborate more
in-house to share talent, resources, and adapt the best ideas to products
that they could adapt for their product family or to introduce an
one-size-fits-all product.

A perfect example is the ESS (Shark) disk subsystem that was originally
designed for the mainframe but adapted with lower-end features and
qualified for lower end hardware without having to come out with four
separate disk products.

At any rate... IBM is big on maintaining compatibility modes throughout
decades of advances in hardware (and software) so it seems rather unlikely
the old architectures will be dropped; more likely it will continue to run
on newer/current hardware in some sort of compatibility mode. It's
impressive when I see a number of older mainframe programs, some about 40
years old, continue to compile and execute correctly on modern hardware.

VMS is nearly as good... I say 'nearly' because there are RTL lib changes
that sometimes breaks application behavior and VMS hasn't been around for
the same 40+ years... but it's still pretty good where you can often
recompile programs from much older VMS versions and still have it run well
today on modern hardware.

So getting back to this thread... I honestly don't think that IBM's going
to suddenly drop older architectures because it would be a major selling
point for their competitors, and IBM prides themselves on giving customers
a good feeling of 'can plan on their current apps working for many years,
even across hardware families' -- which is a major selling point for the
mainframe market. IBM would find a way to make older stuff work on newer
hardware, and it seems that they have done so.

If you ever want to find *the* definitive mainframe information, you could
ask one of the long-time IBM mainframe people... such as Mr. Lynn Wheeler
(now retired) whom typically hangs out in comp.arch and is full of
interesting details about the evolution of the mainframe hardware and
software, and would know this stuff very well.

Also: http://www-1.ibm.com/servers/eserver/zseries/

-Dan

Disclaimer: I don't work for any computer manufacturer or vendor. :-)

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