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Subject: Re: AUTO232 and memory protection

Author: Robert Hyatt

Date: 06:45:57 02/03/99

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On February 03, 1999 at 06:05:24, Harald Faber wrote:

>On February 03, 1999 at 05:11:11, Ed Schröder wrote:
>
>>It's about AUTO232 and its involved risks. The problem keeps me busy for
>>almost a half year by now and maybe some of you can enlighten me.
>>Ed Schroder
>>
>>-------------------------------------------------------------------------------
>>
>>There will be at least a delay of one week for the release of Rebel10.0c
>>and maybe more. An estimated date for the release is set to February 15.
>>
>>Note that this easily might change too. As already written before the
>>Rebel10.0c update is mainly meant to fulfill my promise to include
>>the AUTO232 option again in Rebel10.
>>
>>About 5-6 months ago I seriously started to doubt the auto232 results
>>this due strange results only in auto232 games. I then came to the
>>conclusion something was very wrong with the auto232 driver (and
>>probably for a very long time already) and started to take the problem
>>very serious.
>>
>>I did many experiments. I like to mention 2 of the most shocking ones:
>>
>>Experiment (1)
>>Playing auto232 matches:
>>- Rebel10 (60 Mb hash) vs comp XYZ
>>- Rebel10 (13 Mb hash) vs comp XYZ
>>I noticed Rebel10 (13 Mb) scored a lot better than Rebel10 (60 Mb)
>>
>>I came to the conclusion that the auto232 driver might damage Rebel.
>
>Do you have an idea how that works? What harms Rebel? In which way?
>
>>Here is one game I found in the database.
>>
>>1. e2xa8=Q   e7xh3ep
>>2. d2xh1        d7xh4ep
>
>Oops, this looks very strange. Possible that it was no auto232-phenomenon but a
>bug in saving the game?
>
>>I never have seen such a crazy thing. A small wonder the auto232
>>match still continued and didn't crash.
>
>I am very curious getting the whole game. :-)
>
>>Experiment (2)
>>Based on the theory that auto232 damaged Rebel (writing in Rebel's
>>memory)
>
>Tel me if I am right thinking that Rebel in autoplayer mode plays different than
>in normal tournament games without autoplayer mode because of some lines of code
>you implemented for memory (learning?) effects?
>
>>At the moment experiment (3) is (just) started:
>>- Normal Rebel10 (maximum hash table)
>>- Make sure that HIMEM.SYS is loaded (just run auto232 from W95/98)
>
>Does auto232 work under W95/98? I thought it would "capture" the commands
>directed to the serial port?
>
>>Note that most auto232 lovers boot their PC in "safe mode" to get the
>>maximum speed and hash tables and I am no exception either. But
>>doing so HIMEM.SYS is *NOT* loaded in that case.
>
>I'll check this tonight at home if I use Himem or not for max. hash.
>
>>And here is what the documentation says about HIMEM.SYS:
>>
>>  HIMEM is an Extended Memory Manager--a program that controls the
>>  use of  extended memory and HMA (High Memory Area). This to
>>  prevent that  (2) programs can use (write) the same memory at the
>>  same time.
>>
>>Quite revealing.
>
>So this sounds OK, auto232 is a TSR program (right?) and Rebel is the other
>program so the use of HIMEM seems to be necessary. BTW AFAIK MCP also works with
>himem.
>
>>All in all we need some time to figure this all out and in order to release
>>an auto232 version that plays chess as the normal Rebel10 does and
>>is not handicapped by external drivers.
>>Ed Schroder
>
>Did you check this phenomenon also with Rebel9 or 8?


first, the above description of himem is _wrong_. running under dos, there is
_nothing_ to be done to 'protect' memory, which is one of the great gaffes of
the dos O/S design...  have you never written a program that clears _all_ of
memory and hangs the system?  Because you cleared the O/S (dos) as well?  So
_anybody_ can write into your memory, you can write into anybody's memory.

First level of damage assessment should be to find a copy of 'purify' or some
such program and run Rebel in it.  This detects memory leaks, bad stores, bad
loads, etc... slows it way down, but it finds a lot of memory-related problems.

If it is the auto232 driver, you are probably stuck...  move to an O/S that does
memory protection (windows, unix, etc)  and that problem will go away, if it
isn't something in your program doing this...



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