calculator_guy

Hey guys,

I'm not a hardware geek at all. I've been a software guy since the stone ages. Anyway, recently my beloved laptop started having heat problems. To make a long story short, I pulled out the heat sink, trying to apply some thermal paste and broke some pins off the CPU, got a used CPU on eBay for $21 and replaced it, and (miracle of miracles!) here I am two weeks later typin atcha on the laptop, which SEEMS(?) cool as a cucumber.

The CPU I put in is the same as what came with the puter. The whole process took me many hours of google research, and in the process I THINK I now know a better CPU to put in there. NOT ONE TO REST ON MY LAURELS!! I'll tell you what I think, and you tell me why I'm out to lunch.

My current CPU is a Celeron Northwood 2.70 GHz, 478 pin, 400 MHz bus, 128K L2 cache, SL77S. You can read all the specs here:
http://processorfinder.intel.com/Det...SL77S&OrdCode=

This laptop - a Systemax G732e -- is known to have heat issues because the processor is a desktop processor. The fan runs all the time (it's supposed to) and kicks into high couple times an hour at least. Still, it did last four years, and probably would have lasted years more, except I, being completely unconscious on hardware stuff, let it run overnight playing DVDs, more than once, sitting on a vinyl chair that impeded air flow to the fan.

I know I should search the ECS (real manufacturer) web site to find the motherboard #, but that ain't workin. It seems like they deleted all references to this motherboard.

So I THINK I can upgrade to one of the Centrino processors, as long as it has same or lower wattage (they all do) and the same bus speed and package type (478 pin AKA). Specifically I'm looking at something like this:
http://processorfinder.intel.com/Det...0&sSpec=SL7EN#

an SL7EN with 478 pin package (but no heat spreader) which draws about one-third the wattage and is rated to 100 degrees Centigrade instead of 74 in the SL77S.

These are rated almost the same speed, on CPUbanchmark.net, but the idea is to get something more laptopable in there. I'm betting that the 2M L2 cache won't cause a problem (compared to 128k on the Celeron) because the L2 cache is all on the chip, RIGHT? And I'm betting the new CPU will fit in OK with the big 'ol clunky heat sink that Systemax wisely incorporated.

I'm not looking for a guarantee. I just want someone to tell me if there's NO WAY it can work. Or you can just tell me I'm crazy to not let well enough alone.

Maybe I'm just all stoked up, man. Never fixed NOTHIN before. I'd appreciate an answer within 20 hours, if possible. Summer is comin!

TIA,
c_guy

Fox

I found a partial list of ECS boards on a socket 478 page here. It seems like most of those boards have a limitation of how much L2 cache they can address, and some have slower frontside bus speeds than might be required by a new centrino.

I would figure that the heatsink should be compatible, especially if it was made to handle the more power hungry, and hot-headed desktop chip that's currently in there. Of course, I would clean the old thermal compound off of it and reapply before installing the new CPU.

It's definitely not a guarantee that it'll work, or even that it's risk free (you might want to poke around a hardware IRC channel to see if anyone has done this before), but if it were me, I'd probably give it a try just to see if it works.

calculator_guy

Thanks Fox!

Hard to figure out which 478 socket MB goes with my comfuser. But you know, I saw 512k for L2 cache in the g732 manual, even though I know my CPU has a 128k L2. I never thought it through extra careful.

I was thinking the MB had nothing to do with it -- that the L2 just communicates with the CPU. But I see now the MB has to communicate parts of memory to the L2 cache on its way to the CPU, so the whole crazy scheme can hang together. Or at least, that makes more sense than the CPU handling it both ways.

So now I'm semi-sure the max L2 cache it can address is 512k. So that's going to put a serious crimp in the speed of the Centrino -- if it even works. Which it might not, cause I read somewhere the BIOS might hang if it's not written to look at the whole deal... whole cache I think.

Still, maybe I'll try it out if I can get one for under $30. WAIT! Change of plans! What I'll so is shoot for a Centrino or Celeron M with a 512k L2/478 pins. I'm sure I can get one of those on eBay for around $15. Then I can try it out, just to satisfy my curiousity, and if it works, I have a spare CPU on hand in case the Celeron gets fried again.

Thanks for the input. Keep 'em coming.

c_guy

calculator_guy

... of whether a motherboard must support a given L2 cache size. There is a lot of hokum on the internet about "backside" L2 caches as opposed to "inline" caches. I even saw scholarly looking papers with diagrams showing backside L2 caches connected EXCLUSIVELY to the CPU, with the CPU situated between cache and bus. Nonsense!

Here is the best article I found explaining the real connections:
http://lwn.net/Articles/252125/

There are diagrams with L1i, L1d, L2, L3 etc. in relation to the CPU core and the bus. There is also a section about two-thirds of the way down showing the importance of the bus speed for the operation of the caches -- with actual test results. The conclusion is inevitable that Intel L2 caches ARE NOT BACKSIDE CACHES, no matter what you may read. (Um, maybe AMD has backside caches -- not sure.) They are inline, even when the cache is inside the CPU housing.

Therefore, the motherboard, which provides the separate connections between the cache and the bus, MUST be compatible with the L1 and L2 cache sizes. So I'm now 92% sure that an L2 cache greater than 512 will be wasted on my laptop, and about 70% sure it'd hang at POST. So I'm not going to spend $35+ on that SL7EN. I'm not quite that rich. (No violin smilies?)

So that means I can take my time. No need to bid on the three SL7ENs coming up 2-3 minutes apart in 6 hours on eBay. (That's one of my secrets for getting great deals on eBay. Supply and demand -- think about it.)

More comments are welcome. No time pressure.

Thanx,
google_weary_guy

calculator_guy

I settled on a SL73Y 478 pin, 2.20 GHz Celeron with 400 MHz FSB, and 256 KB L2 cache. I resisted the temptation of a much faster Pentium M with 512 KB cache for $50 (actually a nice deal) and went with the $17 cheapie. I'm glad I did.

I put it in and fired 'er up. I was excited to see the CD/DVD LED flash -- it didn't do that with a dead CPU in there. Then nothing. No POST, no display. No blinking from the USB drive. BUT -- when I held down the power button for five seconds it turned off! That's ANOTHER thing it never did with a dead CPU.

I'm pretty dagone sure THAT MEANS THE BIOS IS RUNNING, RIGHT!? The BIOS just looked at the CPU, couldn't find it on its little list, and decided to choke as a "safety measure" or some dang thin. But the BIOS ain't gonna even count to five without a working CPU in there.

The only thing different in the specs of this CPU with the one that works is L2 cache = 256kb instead of 128. So maybe that's it (maybe Systemax saved 75 cents by using a MOBO that can only go to 128kb) or maybe like I said, it just looks at a list.

So I guess the moral of the story is: If you do brain surgery, try to put back the same brain that you took out.

Thanks for the assistance. I'll go back to my little software life now.

calculator_guy

floydfan

the cpu is fine, the mobo likely just can't support it. even though it is 478 pin, intel made a mobile 478 that is not electrically compatible with regular 478, so no mobile class cpu will work with your board.

calculator_guy

Sounds about right, ff, thanks.

The interesting thing is the front side looks exactly the same as the one that works. Same 478 pins and same pattern of contacts in the middle. Also, I'm pretty sure the five second turn off is a PROGRAM in the BIOS. Otherwise it would've worked with the SL77S that had two pins missing, but it didn't. And it just makes sense that it would be a program. So something is running the program.

BUT, no boot. Just a well-behaved nonboot. ;-)

c_guy