🚀 go-pugleaf

Lawrence Kirby <fred@genesis.demon.co.uk> wrote:
>In article <4rkkhn$54@natasha.rmii.com> underwoe@rmii.com "Edmond" writes:
>
>>Lawrence Kirby <fred@genesis.demon.co.uk> wrote:
>>
>>>Certainly, they are 32 bit applications even running under DOS (they use
>>>32 bit DOS extenders). Only things like disk I/O have o use 16 bit code
>>>and CPU speed isn't particularly relevat there since it is waiting for the
>>>disk most of the time.
>>>
>>
>>32-bit doesn't mean that you are using a flat memory model.
>
>In theory no. In practice with current OSs and extenders that is
>exactly what is means.
>

I disagree.  

>> The latter is 
>>just as important as using 32-bit registers for data.  Segmented memory 
>>causes you to subvert the branch prediction model of the P-PRO which 
>>causes all sorts of processor stalls apparently.  
>
>That and register aliasing are the main things that have given the Ppro a

Register renaming hasn't done this for other processors.  

>bad name for 16 bit apps. 32 bit code give you more flexibility in the
>use of registers and until a 4GB address space ceases to be adequate
>code can use a 'small' memory model.

Segmented pointers are terrible for the PRO.  It kills the branch prediction 
model.  32-bit code is probably less flexible (you can't chop registers in half 
like mov 8,al etc.), but more predictable.  

>>>>And wait for a 
>>>>Pentium Pro built version of Quake for NT 4.0 with Xdirect video and 
>>>>sound. 
>>>
>>>The only reason an NT version would run faster in normal play is if it
>>>were able to use some of the features of the graphics/sound cards better.
>>>This is relevant but not a 16 vs 32 bit code issue.
>>
>>Not exactly.  If the drivers and the graphics API are all fully 32-bit, 
>>you'll get better performance from the 32-bit versions.  Win95 uses 16-bit 
>>graphics (and some video/sound drivers are still 16-bit), so your doomed 
>>to slowdom on a Pentium PRO.
>
>Possibly for some of the control functions but those should have
>insignificant overhead anyway. Access to the screen memory is 32 bit.

Win95 thunks it's 32-bit API down to 16-bit.  You'll see slowdown no matter 
what.  

>Under DOS I would expect it to deal with VGA modes directly, with
>possibly some 16 bit calls for VESA modes.
>

Doesn't matter.  If the data that your using is 16-bit segmented, then you'll 
get a slow down.  

>> WinNT 4.0 would give you much superior 
>>graphics performance under the PRO.  
>
>I doubt whether the difference would be noticable, possibly not even
>measurable except, as stated above, where it is able to take better
>advantage of the graphics/sound card features.

Since I have both Win95 and NT 4.0b2 on my system, I have very few doubts.

-----------------------------------------------------------------------
Edmond Underwood
E-mail:  underwoe@rmii.com
Bench32 1.20 - The new threshhold in system benchmarking.
Bench32 web site:  http://www.rmii.com/~underwoe/bench32.html.