According to the specs I have Serena, the eMachines eTower 633i Desktop PC, uses a TriGem Cognac motherboard.
[TriGem is the manufacturer, Cognac is the model.
Note it is Not the TriGem Cognac+ ]http://www.motherboards.org/mobot/motherboards_d/Trigem/Cognac/
Specifications. (You can click on the photo to enlarge)
PDF motherboard manual,http://www.elhvb.com/mboards/TriGem/manuals/index.html
Click on - Cognac - in the left side of the list.
Going back to the Motherboards.org page;
(Nothing like upside down photo information, and the motherboard is turned 90 degrees to the Right, to how it actually sits in your computer case )
The processor socket is a Socket 370,http://en.wikipedia.org/wiki/Socket_370
Used for Intel Pentium III processors, and intel 'Celey' processors.
An Intel Pentium III processor has TWICE the L2 cache, that a comparable Intel Celeron has.
The cache for a Processor is a small memory area for the Processor.
It is the First memory the Processor accesses.
The Ram Memory is second, and the Harddrive is third.
More cache for a Processor makes it more faster )
The motherboard chipset is an Intel 810.
The Northbridge chip of the motherboard chipset, is an Intel 82810.
The Southbridge chip is an Intel 82801AA, or an Intel 82801AB.
(Intel ICH, or Intel ICH0 )
Looking at the chart, and reading across, you can see what the Intel 810 motherboard chipset supports;
1) Processors: Intel Celeron, or Intel Pentium II, or Intel Pentium III.
2) Processor Front Side Bus: (FSB) 66MegaHertz, or 100MHz.
3) SDR Sdram ram memory at 100Megahertz.
[Single Data Rate Sdram is often just referred to as Sdram.
Double Data Rate Sdram is also Sdram (DDR Sdram)
Synchronous Dynamic Random Access Memory
So is DDR2 Sdram, and DDR3 Sdram ]
Also referred to as PC100.
So when looking for a CPU you look for;
1) Fits in a Socket 370 processor socket.
Yep. The best is going to be an Intel Pentium III.
2) Has a FSB of 100MHz.
Pentium III 1100.
Maximum frequency rate ('Speed') is 1.1GHz (1100MHz)
Front Side Bus = 100MHz
Uses a Socket 370 processor socket.
Part Number = RB80526PY005256
sSpec Number = SL5QWhttp://www.cpu-world.com/CPUs/Pentium-III/TYPE-Pentium%20III%20%28Coppermine%29.htmlhttp://www.cpu-world.com/CPUs/Pentium-III/Intel-Pentium%20III%201100%20-%20RB80526PY005256%20%28BX80526F1100256%29.html
In the top header -
Specifications / Pictures (1) / CPU ID (1) / Comments (1),
click on Pictures (1)
You can click on the photo to enlarge.
256MegaByte of L2 cache. (256MB)
A comparable Celeron would have 128MB of L2 cache.http://www.recycledgoods.com/products/Intel-SL5QW-PIII-Processor-1100-256-100-1.75V.htmlhttp://www.impactcomputers.com/sl5qw.html
[ Don't forget to follow Anti-Static Precautions.
Clean the bottom of the Heatsink THOROUGHLY, and the top of the Processor if it needs it. (I always do anyway)
PROPERLY apply fresh, new Thermal Paste.
For additional questions please post in a Comment.