Author: Christophe Theron
Date: 10:27:00 07/14/98
Go up one level in this thread
On July 14, 1998 at 13:01:37, Amir Ban wrote:
>On July 14, 1998 at 12:24:08, Christophe Theron wrote:
>
>>On July 13, 1998 at 22:45:02, SEAN EVANS wrote:
>>
>>>Hello Amir Ban,
>>>
>>>Will the next verision of Junior be called 5.32 making it a True 32 bit Chess
>>>engine which can utilize the larger BUS.
>>>
>>>Here is a good Newbie question for you! Is it faster for a Chess engine like
>>>Rebel or Mchess to run under a DOS system or a program like CM5500 to run under
>>>a 32 bit system??? It would seem to me the "Newbie" that 32 bits is faster than
>>>16 bits.
>>
>>Chess Tiger is a 32 bits application and exists both in DOS and Win95 versions.
>>
>>The DOS version is compiled with the (free) Gnu C Compiler, which includes a DOS
>>extender. The extender makes 32 bits DOS applications possible. This version can
>>be run under pure DOS, or in a Win95 DOS box.
>>
>>The Win95 version can be compiled either with Microsoft C Compiler (version 4 or
>>5) or with the Borland Compilers. The fastest engine is obtained by using the
>>Microsoft Visual C version 5.
>>
>>Running the DOS version under pure DOS is as fast as running the Win95 version
>>under Win95.
>>
>>That is to say: the environment you are using (DOS or Windows) makes very little
>>difference. Pure DOS should theorically be slightly faster than Windows, because
>>of Windows real time multitasking overhead. In pratice, the MSVC5 compiler is
>>slightly better in producing optimized code, and I see no difference between DOS
>>and Windows.
>>
>>So I keep using DOS for my competition engine, because with the same amount of
>>available RAM I can get more hash (Windows is not eating memory).
>>
>>If I released Tiger, I would certainly do it as a Windows application, because I
>>don't want people to say: "Hey, this is a crappy DOS program!". Yeah, some
>>people really react like that...
>>
>>And one more thing: I'm quite sure that Tiger would be a little bit faster if it
>>was a 16 bits (DOS or Windows) application. So why did I use 32 bits? Because it
>>is a little bit trickier to program a large application in 16 bits, and I was a
>>little bit too lazy for that.
>>
>>As you see, things are not as simple as: "16 bits DOS programs suck".
>>
>>
>> Christophe
>
>
>This is not too clear to me.
>
>Is your program a 16-bit program or a true 32-bit program ? The division is not
>sharp because even in real-mode you can use many of the processors 32-bit
>features, such as the extended common registers. So I will clarify: A true
>32-bit program uses a 32-bit stack and has ESP as the stack pointer. A 16-bit
>program uses a 16-bit stack and SP as the stack pointer.
The GCC compiler creates true 32 bits programs. And with the provided DOS
extender, it even brings virtual memory (with swapping to disk if necessary) to
these "DOS" applications.
>A DOS program can't possibly be a true 32-bit program. If you are using a DOS
>extender, then you are really not really using DOS. The extender creates an
>environment that is really a different O/S, and the DOS interface is a
>simulation. If the extender is 32-bit flat (some extenders are not), and the
>program is 32-bit, then it's just as good as running on Win32.
That's the case.
Of course the extender is somehow a different OS, essentially taking care of
linear memory organization, but the 32 bits applications end up using the DOS
file system for example. And from the programmer's point of view, it's just DOS
applications without the segmented memory limitations...
>You can use the full instruction set and addressing modes of the CPU only in
>32-bit programs. This, and the fact that Intel is optimizing for years for
>32-bit, makes 32-bit programs generally faster, sometimes much faster.
Maybe 16 bits applications will be penalized with the new processors. But the P5
runs 16 bits applications as fast as previous processors. And the fact that 16
bits code is a little bit more compact can make a real difference in L1 cache
performance. Especially on a chess engine.
Christophe
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