# 533mhz bus chips hard to OC ?

#### Takumi

##### Registered
I want to hit 3ghz as easily as possible. I've been thinking about buying a 2.53ghz or 2.66ghz chip to do it... but I think I've calculated some bus speeds that scare me...

2.53 x 119 = 3010.7
Memory 333x119=396
FSB 533x119=634

2.66 x 113 = 3005.8
Memory 333x113=376
FSB 533x112=602

Any suggestions ? or this a piece of cake ?

#### batboy

##### Senior Moment
First off, I don't have a clue what you're trying to calculate.

2.53 gig=2530 MHz=19X133 FSB (19X is multiplier)

So, 19X158 FSB=3002 MHz or 3 gig

2.66 gig=2666 MHz=20X133 FSB (20X is multiplier)

So, 20X150 FSB=3000 MHz or 3 gig

Now, for memory... DDR memory is Double Data Rate, so 133 FSBX2=266 or you need to use PC2100 at 1:1 memory ratio. Of course you'll actually want to use 3:4 setting for better performance and you'll want to overclock too. So, if you are running 150 FSB and want to use the 3:4 ratio, you'll have the memory bus at 200 MHz. Therefore, you'll need at least PC3200. If you want a little more magin for overclocking and error, than use a higher rated DDR.

Here are what the DDR modules are rated for:

PC2100 - 133 FSB
PC2700 - 166 FSB
PC3000 - 183 FSB
PC3200 - 200 FSB

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#### Takumi

##### Registered
So... 533mhz fsb isn't really 533, but 133 ? So, taking a 2.66ghz chip to 3ghz does not increase the fsb from 533 to 600 ?

Or the 2.53ghz chip to 634mhz fsb ?

Aside from the numbers... if I want a reasonably priced chip to hit 3ghz, what's my best bet ? Is there the 2.66ghz chip worth an extra \$67 over the 2.53ghz chip, if 3ghz is my goal ?

#### batboy

##### Senior Moment
The P-4 has a quad pumped bus, so 133 FSB is 533 MHz bus speed, but you'll confuse yourself worrying about all that, because the FSB is still 133 MHz (133X4=533). Just use the FSB to calculate stuff and you'll be ok.

I'd save your cash and get the 2.53 CPU if you can find a C1 stepping (1.525v default voltage). All 2.66 CPUs are C1 stepping. I have a 2.66 and most will easily do 3+ gig. Think about getting some good Corsair XMS DDR memory regardless of which CPU you choose.

##### Member
pentium 4 bus is "quad pumped". 100 x 4 = 400. 133 x 4 = 533.

so thats 600 and 632, yes.

my guess would be that a 2.26 would be best. but i dont know p4s that well.

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#### Takumi

##### Registered
Based on what I've read about hard to get C1 stepping 2.53ghz from discount places like Newegg, Googlegear, etc... and the cost difference between them and the local store...

If ALL 2.66ghz chips are C1 stepping and seemingly easier to hit 3ghz with...

I'm guessing I can get a 2.66ghz from Newegg, etc for what I could find a C1 2.53ghz at a local store, etc...

#### Jupiler

##### Registered
Personnaly, I'd go for a 2.66 Ghz then.
If you say that the price difference between a 2.53 from your local store and a 2.66 from newegg or other store is so small, then the choice isn't that diffcult, IMO.

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#### Takumi

##### Registered
Just making sure I wasn't making some dumb mistake... I've been out of the o/c "scene" for a while...

And just when I was ready to order a 2.66ghz, I remembered back to the days when buying a 333mhz or 366mhz Celeron instead of a 300a was not only a waste but really had less potential.

There are rare occasions when cheaper is better, just thought I'd look before I lept. Also I considered that maybe 133/533 bus speed could be near the upper limit of fsb and maybe I'd be better off getting a 100/400mhz proc.

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