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View Full Version : Using a 1/2 multi, why is this BAD?


newls1
07-05-05, 03:19 PM
I did some searching, but really could find my answer. I'm wanting to take my FSB (HTT) from 262Mhz, to 260MHz and increase my mutli from 11x to 11.5x. What are the dis-advantages when doing something like this? I read where is screws with your ram divider, etc.... but is all this true...? thank you

Riptide
07-05-05, 03:23 PM
It's not bad per-se. But if you use a half multiplier for your CPU you won't gain any extra bandwidth for your memory. IOW, 200x10 = the same bandwidth as 200x10.5.

newls1
07-05-05, 03:45 PM
It's not bad per-se. But if you use a half multiplier for your CPU you won't gain any extra bandwidth for your memory. IOW, 200x10 = the same bandwidth as 200x10.5.
OK, with that said, would you agree with this: "IF" 1 "JUMP UP" in a multiplier = 200Mhz, then a half multi = 100Mhz, then this mean that if I can GAIN 100more MHz (stability being of a concern) and still use my 260+FSB for my memory bandwidth, then wouldn't that 100MHz increase be benificial?

$n][pErMan
07-05-05, 06:32 PM
OK, with that said, would you agree with this: "IF" 1 "JUMP UP" in a multiplier = 200Mhz, then a half multi = 100Mhz, then this mean that if I can GAIN 100more MHz (stability being of a concern) and still use my 260+FSB for my memory bandwidth, then wouldn't that 100MHz increase be benificial?
Ok .. I think what your saying is if you wanna keep the same FSB (for stability reasons) and up the multiplier on the CPU to only gain frequency increase in the CPU and not the FSB... if thats good? Assuming you cant increase your FSB more but can still be stable at a higher multiplier with that FSB .. then yes... its good.

newls1
07-05-05, 06:50 PM
**UPDATE** I tried to use the 11.5x multi, but the computer wouldn't post. The CPU really needs more Vcore, but 1.636 is all I can do with my cooling. Ol-well, it was worth a try.....

rflair
07-05-05, 07:30 PM
This nice chart shows you why you shouldn't, or should

http://www.xtremesystems.org/forums/showthread.php?t=41595

You lose memory bandwidth with half multipliers in the higher FSB range.

newls1
07-05-05, 07:38 PM
thanks, that is a great chart....

nIghtorius
07-06-05, 11:44 AM
The Atlhon64's memorycontroller has a divider..

memory speed=

("FSB" * Multiplier) / (memdivider) = xxx Mhz

memdivider ~= Multiplier, but when multiplier is 10.5x then memdivider will be 11.
when multiplier is 11.5, memdivider = 12, etc.. only when multiplier is xx.0 then memdivider will be xx.0 (equal)

so when running a 260 Mhz "FSB" @ 10.5 multiplier your memory speed is.
memspeed = (260 * 10.5) / 11 = 248Mhz

and @ 10.0 multiplier it is.
memspeed = (260 * 10) / 10 = 260Mhz

see?

john19055
07-24-05, 12:10 AM
I can't never get it to come out right when I try to use half multiplers.

Lfctony
07-25-05, 08:47 PM
Using a half-multi suits mine as I'm using the 1.5 bios for my mobo, which doesn't allow me to post with HTT at above 230. I can't be bothered to flash back to 1.2 again, so I'm running at 10.5x229, ram is at 200 exactly, system seems stable so far.

rflair
07-26-05, 09:02 AM
Using a half-multi suits mine as I'm using the 1.5 bios for my mobo, which doesn't allow me to post with HTT at above 230. I can't be bothered to flash back to 1.2 again, so I'm running at 10.5x229, ram is at 200 exactly, system seems stable so far.

And thats all that really matter, a nice stable system. :)

Lfctony
07-26-05, 09:20 AM
Well, it was stable, I'm back to stock again. System failed to boot and the screen was garbled in Windows. I restarted and Windows reported a critical error on any of 4 things including CPU and motherboard. So it seems it's not stable after all. :(

jAkUp
07-26-05, 01:01 PM
Yea, don't use half multi's. They cut your memory speed. I really don't understand why though...

nIghtorius
07-26-05, 02:37 PM
Yea, don't use half multi's. They cut your memory speed. I really don't understand why though...

I thought I had explained this?!... :eek:

wait.. :P

I did..

The Atlhon64's memorycontroller has a divider..

memory speed=

("FSB" * Multiplier) / (memdivider) = xxx Mhz

memdivider ~= Multiplier, but when multiplier is 10.5x then memdivider will be 11.
when multiplier is 11.5, memdivider = 12, etc.. only when multiplier is xx.0 then memdivider will be xx.0 (equal)

so when running a 260 Mhz "FSB" @ 10.5 multiplier your memory speed is.
memspeed = (260 * 10.5) / 11 = 248Mhz

and @ 10.0 multiplier it is.
memspeed = (260 * 10) / 10 = 260Mhz

see?

The AMD's memory controller has only full multipliers.. that's why it does that..

jAkUp
07-26-05, 03:05 PM
lol sorry, I guess I should read past the first post :D