MTRR0, MTRR1... What do these do

Ye Olde Forum · Post by **Ye Olde Forum** » Sat Jun 02, 2001 11:20 pm

[Desert_Dog] Posted 6-1-2001 11:26 I have a K6-III+ chip and use Rob's CTU utility to tweak my settings and was wondering just what the MTRR0 and MTRR1 settings do and why only MTRR1 is activated on mine ?? I have done a search on Google and came up with squat for an indepth explanation on the 2 settings that I can understand. ____________________ From the Arizona Desert Where seldom is heard, a discouraging word, unless you connect @ 24000 all day. -------------------- AMD K6-III 450+ o/c to 550 @ 2.0 Vcore Tyan S1590S AT100 Award BIOS 162005096 1998 V90W116c Flash V90j116c Over Flash 3DFX Socket-AHO heatsink w/ADDA 28cfm fan 3DFX Case80HO 80mm front Fan Arctic Silver Thermal Compound 256MB Crucial CL2 PC100 Promise Ultra100 IDE Controller WD 300BB 30GB ATA-100/7200 Radeon VE 32MB DDR U.S.Robotics 56K Win Int 1125-04 R:2 SB Live X-Gamer USB Scanner/Printer Belkin 4 port USB hub Windows Millennium ____________________

Ye Olde Forum · Post by **Ye Olde Forum** » Sat Jun 02, 2001 11:21 pm

Posted 6-1-2001 13:08 write combining mtrr0 is for video memory write combining mtrr1 is for main memory & aperture size all of this is done in the cache basicly they tweak your video proformance and is yet another feature that the K6-2 does not suport.

Ye Olde Forum · Post by **Ye Olde Forum** » Sat Jun 02, 2001 11:22 pm

Posted 6-2-2001 04:06 Well, not quite true. The k6-2 actually DOES support the MTRR registers in the exact same fashion that a "+" CPU does (they are identical in functionality). The registers are used to define areas of memory where the memory writes are not cached so that video image updates are as quick as possible on the screen. Video drivers use the two registers interchangeably. Your ATI drivers use the MTRRs, and if you fire up an mpeg player, you'll probably see both registers in use (one is used for the LFB or linear frame buffer memory region normally mapped way above physical memory, and the second MTRR is used for "overlays" useful in displaying video). This is what I've noticed with my ATI rage128 drivers. Nvidia drivers also make use of the MTRR registers, so changing them to some value other than what the driver has setup is likely to harm the performance of your system. The above reasons are why I have not allowed the user to enter data for these registers with k6speed, too many simply do not need to alter the registers, or may actually do harm to their system performance (or cause other problems) by entering MTRR range/size values that are inappropriate or erroneous. I recognize that some video card drivers fail to setup these registers, but there are other tools available to set them up (best I've seen is setk6v2).

Ye Olde Forum · Post by **Ye Olde Forum** » Sat Jun 02, 2001 11:23 pm

Posted 6-2-2001 12:49 bronx69, kylesb Thank you both for you're responses, I'm another day smarter now and better understand the subject than I did before. I did enter a value for MTRR0 (just for shits and giggles) where Rob's CTU program had left it grayed out, and my screen went blank and my system auto rebooted. Yea, I read his warning about If you don't know what you're doing then leave it alone. Just wanted to see what would happen though, no damage done. What I find interesting is the fact that I got not much of a responce when I used GOOGLE to search on the subject, you guys are better than a search engine. When it comes to the in-depth stuff like this I'm afraid that I'm a little short on one end. I don't like to ask the same question that has been asked a hundred times before so I first tryed a search over at AMDZone, didn't know what happened, but I came up with ZERO response, After reading the other posts this morning though I see that things are kindof on tilt over there right now, but the search function always worked before. Again, THX guys for you're response. ____________________ From the Arizona Desert Where seldom is heard, a discouraging word, unless you connect @ 24000 all day. -------------------- AMD K6-III 450+ o/c to 550 @ 2.0 Vcore Tyan S1590S AT100 Award BIOS 162005096 1998 V90W116c Flash V90j116c Over Flash 3DFX Socket-AHO heatsink w/ADDA 28cfm fan 3DFX Case80HO 80mm front Fan Arctic Silver Thermal Compound 256MB Crucial CL2 PC100 Promise Ultra100 IDE Controller WD 300BB 30GB ATA-100/7200 Radeon VE 32MB DDR U.S.Robotics 56K Win Int 1125-04 R:2 SB Live X-Gamer USB Scanner/Printer Belkin 4 port USB hub Windows Millennium ____________________

kylesb · Post by **kylesb** » Sun Jun 03, 2001 9:37 am

Usually, for very technical info, a search of the Google-groups is worthwhile. Here's the URL I use (the advanced search page): <a href="http://groups.google.com/advanced_group ...

monaro327 · Post by **monaro327** » Mon Jun 04, 2001 4:23 am

my k6.2 will work with mtrro mtrr1 in ctu i think only the k6.2 with the cxt core support it i can not put them higher then 256kb is this normal

kylesb · Post by **kylesb** » Mon Jun 04, 2001 11:05 am

I may have failed to provide complete info. Yes, the CXT core and newer K6-2 CPU's (model 8 and above) are the only AMD CPUs to support MTRR regs. Further, the maximum programmable range for an MTRR register is 4 gig (yep, that's gig), minimum range size is 128 kb. Best regards,KyleK6speed URL:http://msnhomepages.talkcity.com/cerfst ...

monaro327 · Post by **monaro327** » Tue Jun 05, 2001 12:29 am

why can i only put it to 256k higher and it crashes

kylesb · Post by **kylesb** » Tue Jun 05, 2001 9:11 pm

What base address are you using with a range of 256Kb? My ATI Rage128 sets up a 128meg range register at base address E000000h. When I play Mpeg files, As I've said before, if your video driver is already setting up the registers (one or both), don't mess with them. Further, the code in CTU may be failing to properly setup the registers for you. Best regards,KyleK6speed URL:http://msnhomepages.talkcity.com/cerfst ...

RobM · Post by **RobM** » Mon Jun 11, 2001 11:27 am

<blockquote>Quote:<hr> Further, the code in CTU may be failing to properly setup the registers for you.<hr></blockquote> Please explain what you mean by this.

monaro327 · Post by **monaro327** » Tue Jun 12, 2001 1:59 am

yeah what do you mean and why is it stuffing up when i set it over 256k

K6Plus

MTRR0, MTRR1... What do these do

MTRR0, MTRR1... What do these do

[bronx69] write combining

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[Desert_Dog] MTRR0, MTRR1... What do these do

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