From: ADUNSMUI@TOROLAB6.VNET.IBM.COM (Al Dunsmuir)
Date: Fri, 28 Aug 92 16:18:21 EDT
Newsgroups: comp.os.os2.misc
Subject: Re: OS/2 Win3.1 support *better* than MS!
Organization: IBM Canada Laboratory Ltd, Toronto, CANADA
Disclaimer: This posting represents the poster's views, not those of IBM
News-Software: UReply 3.0
            <pathak-280892123631@virtual.mitre.org>

In <pathak-280892123631@virtual.mitre.org> Heeren Pathak writes:
>In article <1992Aug28.044505.2361@news.Hawaii.Edu>,
>tholen@galileo.ifa.hawaii.edu (Dave Tholen) wrote:
>
>> You know, every once in a while, I'd really like to find out exactly why it
>> is that one company is able to do something that another company can't.  This
>> is a case in point.  If IBM is able to make OS/2 run Windows 3.0 applications
>> that Windows 3.1 can't run, why or how are they able to do it?  Does IBM
>> know something that Microsoft doesn't?  Or does Microsoft know something
>> that IBM doesn't?  Will OS/2 users run into hidden gotchas that Microsoft
>> already knows about, which might be why they designed Windows 3.1 to be
>> incompatible with some Windows 3.0 applications?  Or has IBM found a clever
>> solution to a problem that Microsoft couldn't solve?
>>
>
>From what I understand, MS was forced to make Windows 3.1 incompatible with
>some Windows 3.0 apps to protect Windows from a misbehaved application.
>Since the Windows kernel is located in the same memory space as a Windows
>app, the app can cause the entire environment to crash.  MS put firewalls
>around the kernel to trap a "bad" application.  This firewall doesn't make
>Windows crash proof, it just makes it a bit more crash resistant.
>
>OS/2 doesn't need this "extra" protection.  It all ready gives each process
>a separate, protected address space which is enforced by the hardware.
>Thus, IBM can keep the code which lets Windows 3.1 run faster while
>throwing out the firewall code.
>
>> Another case in point is memory boards for PS/2s.  IBM says that the system
>> maximum memory for a Model 70-A21 is 16 Mbytes, yet there is a large number
>> of third party vendors who will sell Microchannel memory boards that support
>> more than 16 Mbytes on this model.  How do they do it?  Do they know something
>> IBM doesn't know?  Or does IBM know something that the third party vendors
>> don't know, like some sort of hidden gotcha when dealing with more than
>> 16 Mbytes on such a machine?  I've asked a local IBMer why these third party
>> folks are able to provide more than 16 Mbytes, whereas IBM says 16 Mbytes is
>> the maximum, but I didn't get an answer.  Why is it so hard to get a straight
>> answer to a simple question?
>
>This is probably more a marketing thing.  A vendors product line is
>generally designed so a certain class of users buy a certain type of
>machine.  By limiting the Model 70 to 16M, IBM is trying to encourage
>people who need more than 16M to buy a different machine.
>
>-------------------------------------------------------------------------
>Heeren Pathak                      | Millions long for immortality who do
>pathak@mitre.org                   | not know what to do with themselves
>Mitre Corporation                  | on a rainy Sunday afternoon.
>(617) 271-7465                     |                      -- Susan Ertz
>-------------------------------------------------------------------------
>Disclaimer: Mine not Mitre's.
>

  It's a wee bit simpler than that...

  When the marketting announcement for an IBM PS/2 (or PC) is published,
it contains the specifications for that unit.  IBM will only publish specs
for those features which have been fully tested _at_the_time_of_announce.
If IBM didn't make a memory card which supported more than X MBytes when
the Model 70-A21 was announced, the announcement can show the maximum
configuration which was tested.

  As various feature cards (such as memory) are produced, their respective
announcments will show the machines in which they are supported.  Systems
like the PC/AT "grew" from supporting fairly small amounts of memory to
supporting a full 16M as time went on.  Sometimes system board, BIOS or
reference disk changes were required to make it all happen.  Combinations
of feature cards and systems not in the announcments _may_ work to various
degrees: 100%, mostly, or not at all.

  As other postings have noted, many of the older Model 70's and 80's use
a DMA channel for memory refresh, and since the DMA channel was limited
to 16 MBytes any additional storage must be refreshed by circuitry on the
memory card. The BIOS (or ABIOS for OS/2) routines probably would also
have to be updated to support that extra memory too.  At some point, the
upgrade process becomes too comples/costly and you either accept the
limitations, or buy a new motherboard/machine.

Al Dunsmuir                       Internet: adunsmui@torolab6.vnet.ibm.com
CODE Development II + TEAM OS/2      Voice: (416) 448-3315
IBM Canada Laboratory Ltd, Toronto, CANADA

OS/2 V2: Why settle for anything less?
Newsgroups: comp.os.os2.misc