View Full Version : processors multiplier or DIP switches: who takes precedence?
reupbert
10-14-2002, 05:39 AM
Originally posted on OCF (http://overclockersforum.com) and slightly modified with new information...
I recently purchased a Compaq Deskpro EP on eBay. It has the 440EX chipset, meaning a front side bus of 66mhz. The DIP switches on the motherboard allow for slot 1 processors up to 400mhz. Now, if I were to purchase a socket 370 celeron 766mhz (66mhz FSB) and use a slocket converter, would the locked multiplier on the celeron override the DIP switch maximums? Or would I have a seriously underclocked machine? Is there any way to mod a slocket or motherboard to accept higher multipliers than the DIP switches allow for?
My friend said it was impossible and explained it to me like this: If you throw in a PC133 stick in a 100mhz FSB system, it doesn't raise the FSB. My viewpoint is too skewed - I want this to work badly. So I'm asking someone to explain this to me :(
reupbert,
Welcome to Xtreme :)
I don't think you can use a CPU w/ a higher multiplier than that board will support. If it works at all, it will prolly default to the highest mult available. And as far as the memory, your friend is correct. If you put PC133 in a system that only supports PC100, it will run @ PC100 speeds :(
reupbert
10-14-2002, 06:30 AM
NB, thanks for the fast response. The more I thought about it, the more I realised how unrealistic my hopes where; my friend's analogy brought me down to earth. It's the classic example why my other system can only take an AMD XP 2000+ because the highest multiplier on it is 12.5 times 133mhz FSB equals 1,662.5mhz - if I threw in an XP 2100+ it would be underclocked :eek:
docah
10-14-2002, 06:38 AM
The cpu is locked. the multiplier will not change.
If it's a 66mhz fsb chip and you put it on a 66mhz fsb board it will either post at rated speed or the motherboard will not post because it doesen't recognize the cpu. It's that simple.
Your AXP board won't make a locked chip run a lower multi because it can't support it. It either won't post or will run rated speed.
reupbert
10-14-2002, 08:24 AM
Ok... I'm confused again then. Back to the Compaq Deskpro EP, if I throw a socket 370 celeron 766mhz (66 FSB) into a slocket for the slot 1 on the motherboard, it will either run at 766mhz or not run at all? It won't underclock to the highest multiplier?
If the CPU has a locked multiplier, which it sounds like it does, nope...won't work, sorry.
reupbert
10-14-2002, 10:04 AM
Gotcha. By the way, thanks for helping out a neophyte. I read somewhere that BIOS updates can fix limited multiplier options - although I highly doubt Compaq would go to the trouble of writing a new ROM to allow for newer celerons. And, since I'm insane, how hard would it actually be to write a ROM for a BIOS? I know I would have to have intimate knowledge of how the 440EX chipset works and so forth - are they written in assembler? Should I hire a guru? :p
MrIcee
10-14-2002, 10:21 AM
Let me add in a little insight on this:
I have a Compaq Presario that I wanted to update the CPU in...it's currently a 450 P2. After much research I found the definitive answer directly from Compaq.
The multiplier adjustents on the early boards were implemented because obviously the P2's had multiplier adjustments, which the P3's did not.
With a flash of the last latest bios, which supported P3's, I am able to use any P3 with a 100Mhz FSB...including the P3 1000/100. I had not upgraded as I built my AMD system at about that time, but read many other users successlly running 800-1000Mhz 100Mhz FSB P3's s in their original Compaq's equipped with P2 400-450's(100Mhz FSB) The locked multiplier supercedes the multiplier adjustment of the mainboard.
The same could also be the case with your 66Mhz CPU.
Randi:D
reupbert
10-17-2002, 08:41 AM
Well, some hopefull news. I read in some off-site (read: third party) website that at least 500mhz is attainable with the Deskpro EP (thats the 440EX chipset mobo, with 66mhz fsb). So that means a multiplier of 7.5, which justifies buying a slocket converter for a 500mhz celeron (socket 370) :D
I am going to try flashing the BIOS :flame: with the one intended for the 440BX version... In that case, I could run the highest chip I wanted on 66mhz fsb <evil grin> but then again, I may get screwed over :smileysex and have to remove the CMOS battery and go back to normal BIOS.
docah
10-17-2002, 10:17 AM
Reup ... if you mis flash the bios i have a feeling it will be a little harder to recover than removing the cmos battery. If i recall the bios is stored in some form of programable typically read only memory. Which means you would need to swap it with a bios chip on another board while running to reflash it. (i think, i've never done that though...)