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"Observations of a Would-Be PII Overclocker"

by Mike Langieri


There seems to be a good number of FAQs and other documents on the Celeron processors and their ability to be overclocked successfully. There also seems to be a growing shift in the comments on alternatives to the Pentium II series, and more specifically… the PII-300MHz processor. I thought it might be helpful to piece together a document of questions and answers that are culled from various newsgroups and forums where the PII processors and related issues are being discussed. Maybe some of this info will be redundant, but perhaps some folks contemplating a overclocked system might want a few questions answered before they take the plunge. There are also some general comments on cases, cooling, and motherboards as well. This is just one collection of data and hopefully it’ll continue to grow as more information is gathered. Just remember one thing… although many are having success with the PII, there is also the possibility that you will not be able to overclock your system to the same levels as another guy. If anyone out there has definitive information on any of these observations, please feel free to email me and we’ll try to improve the document on the fly.

Q. What is behind the theory that SL2W8 or SL2YK chips are “really” PII 450’s in disguise?

A. Rumor has it that since the PII-300 and the PII-450 use the same .25 micron core, production facilities, and basic design, Intel is just marking some production batches as 300MHz. Another rumor indicated that since the 300MHz spec might only need a slower L2 cache, Intel might fit those PII-300’s with the slower 5.5 cache. This is hard to confirm.

Q. How does one visually determine which L2 Cache is inside the PII chip?

A. One suggestion I’ve heard to check on a cpu’s cache is look through the holes on the back of the chip casing. Supposedly, if you see the 2 cache chips on one side, you have a 450 with 4.4ns cache. If you see the cache chips on both sides (1 on each side), you have a PII with the 5ns (or higher) cache chips. The 5ns cache can be fine… If you’re able to OC it to 504, you’ll supposedly see better performance than with the 4.4’s due to cache timing. The difference in performance is supposedly rather small, though.

Q. There seems to be a question about how you get a PII-300 like the SL2W8 (OEM) or SL2YK (boxed) to go to 400MHz (or higher) without unlocking it’s internal clock.

A. It can’t be done that way because It’s clock locked at 4.5X. So all you can do is change the FSB of the CPU using jumpers or BIOS setup on the motherboard. You may be able to get up to 450 (4.5X100), 464 (4.5X103), or even 504 (4.5X112). It depends on your motherboard, memory and even the cache.

Q. Are there any special production runs that a buyer could look for to guarantee an overclockable PII-300 either OEM or Retail Boxed?

A. There are no “guarantees” but some guys have reported that the following week/country combos have done well:

Week 37 – Costa Rica SL2W8 – 504MHz stable @ 2.0v
Week 37 – Unknown SL2YK – 504MHz stable no voltage noted
Week 32 – SL2W8 – Costa Rica – 450MHz stable @ 2.0v
Week 33 – Malay SL2YK – 560MHz stable – 5.0ns L2 Cache
Week 41 – Costa Rica SL2W8 – 504MHz stable @ 2.2v
Week 38 – Costa Rica SL2W8 – 450MHz stable @ 2.0v
Week 36 – Costa Rica SL2W8 – 504MHz stable @ 1.97v
Week 40 – Costa Rica SL2W8 – 504MHz stable @ 2.2v – 5.0ns L2 Cache
Week 39 – Unknown SL2W8 – Won’t go 450MHz

Q. Is there any kind of test procedure that can be used to determine the L2 cache speed in the SL2W8 or SL2YK?

A. Apparently there is a cache test file called CTP2 info that is pretty reliable. Supposedly you run the cache test file with your CPU running at 300MHZ (66×4.5) and record the number you get under dos 640k mode. This should reveal the speed of the cache you have. You have to run the file in DOS mode, so restart the computer and choose restart in dos mode. One guy picked up three week 37 SL2Yks and his number was 263.3 mb/s (5.5ns). Anyway, the following list will give you some guidelines:

290-310 MB/s = 7ns
290-260 MB/s = 5,5ns
260-245 MB/s = 5ns
245 MB/s and lower = 4ns

Q. Is there any credence to the theory that you can “burn-in” a chip and over the course of time actually improve it’s performance?

A. Interestingly enough, there haven’t been many posts that _deny_ this, but there have been a lot to say that users have been able to drop core voltages in minute increments and subsequently get a machine to run more stable at some higher overclocked speeds. It’s an interesting phenomenon.

Q. Are all PII-300’s overclockable to PII-450 levels?

A. The original PII-300 Klamath chips (.35 micron) are supposedly far less likely to be overclockable than the newer Deschutes (.25 micron) chips. Klamath chips can be identified on the first line of the product code where you’ll see a sequence like 80522 where the second “2” IDs a Klamath and a “3” IDs a Deschutes. See the breakdown below.

Q. How does one decipher the various product codes on the Intel Pentium II series so he/she would know what they are buying?

A. Again, there are no guarantees that any chip will overclock, but here’s what the (typical) codes mean of a PII-300 SL2W8:

80523PX300512EC SL2W8 ©’96
18350551-0390 Philippines

8052 = 6th generation processor (2.0v)
3 = Model 3 (Deschutes – .25 micron)
PX = Bulk/OEM Tray Processor
300 = Rated Processor Speed (300MHz)
512 = L2 cache size (512K)
EC = L2 Cache supports ECC (error detection/correction)
SL2W8 = Intel sSpec number
©’96 = Copyright information (not date of manufacture)

1 = Philipines (country of fabrication)
8 = Year of manufacture (1998)
35 = Week of manufacture (Sept 97)
0551 = FPO number(test lot traceability number)
0390 = Serialization code
Philipines = Country of origin

NOTE: Intel uses several different code schemes with two (PII) lines and three (PII-350/400) lines on OEM or Boxed cpus, so you may have a little deciphering to do. The fisrt digit in line two could also be a letter like “R” which is another way of indicating Philippines.

"Observations of a Would-Be PII Overclocker"

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Q. What are the specific country product codes?

A. Normally, you’ll find the country of origin printed right on the chip as well as on the package, but here’s a few chip codes:

0 = Costa Rica
1 = Philippines
6 =
8 =
9 = Malaysia
R = Philippines

Q. What does the term “stepping” mean?

A. Stepping is a term used by Intel to note revisions in a production run. For instance, Stepping “0” means it’s the original production run, and then if the engineers discover a bug or wnat to enhance something in the next production run or product spec, the change would be the next higher increment (i.e. Stepping 1). It stands to reason that the latest chips would be the most stable. Some vendors will be able to give you the stepping information before ordering.

Q. What’s the best motherboard for overclocking?

A. “Best” is such a subjective term. There are loads of excellent motherboards out there, but the overwhelming choice in the Fall of 1998 seems to be the Abit BH6, mainly because it’s small, well-featured, and it uses a “jumperless” system whereby you can change the parameters of the motherboard in the bios setup. It is also very reasonably priced.

Q. What’s the best overclocker speed or multiplier?

A. By design, the optimum clock speeds are 66MHz and 100MHz because the motherboards and cpus have been designed with these speeds as defaults for different PII processors. Also, peripherals can start to act cranky when the PCI and AGP clocks are pushed above 33 MHz (PCI) and 66MHz (AGP). Some components have a higher tolerance to overclocking than others, so it pays to ask around before buying that new hard drive or video card.

Q. Is there any advantage to a motherboard like the Abit BH6 where you can adjust Core Voltage of a Pentium II?

A. In theory, no… but in practice, it seems that almost every OC’er that is using the SL2W8/SL2YK with a BH6 is tweaking the performance in exceptionally small increments. I have seen postings down to 1.97v up to 2.4v. Part of the “burn-in” crowd also seem to feel that the voltage can be reduced once the machine has been run in and is stable.

Q. Should the ATX power supply fan blow in or blow out of the case?

A. There seems to be a big school of thought that since the power supply fan is the most powerful fan in the PC, it might make more sense to have it exhausting the heated air since it is normally in the top rear of the housing. Remember heat rises, so the hottest air will be trapped in the topmost half of the case.

Q. What sort of features should be looked for in a “overclocker’s” case?

A. First, try to find a case that is ATX compliant, and not one with a converted AT case power supply. Next, make sure the case has a vent of some sort near the bottom, probably in the front. A lot of new cases have decent front vents and fixtures for secondary fans, and few even have removeable air filters. The trend also seems to be to go with a case that has a slide-out tray, and a minimum of hardware (screws) that can get lost in the crevices of the motherboard and or the case. I like a case that also has at least one removeable side panel.

Q. Should I run my overclocked system without the case cover on?

A. When setting the system up it is obviously OK, but remember that a case is normally designed to operate best when the cover is on so that there is some airflow over the motherboard. Leaving the cover off does not help this… it only hinders it as now you are relying only on the immediate chip fan to cool the cpu. The power supply is drawing in room air which is great for the power supply, but does nothing for the motherboard/cpu/video card. There is something to be said for creating constant airflow _over_ the specific components as opposed to just having an open box system. Think of it in terms of “wind chill factor” to put the airflow issue in perspective.

Q. What about using a peltier cooling system with a PII cpu?

A. Probably the most often asked question on this topic I’ve seen is with regards to STEP Thermodynamics cpu/cooler combos. They have received a lot of criticism from purists that question STEP’s marketing hype on their web page, but when you get by all that, the bottom line is that they are selling a custom-assembled cpu/peltier/heatsink combo that is bench-tested at a given processor speed setting and guaranteed for life. I’d like n it to Plug’n Play Overclocking!

Q. How does STEP guarantee the processor speeds they advertise?

A. STEP claims to hand pick the processors they use, and I’d guess that they also have a good source for known overclockable cpus. I found it very interesting that they can find PII-333’s that are not normally known for being overclockable, and guarantee them to make 500MHz with a 5.0X100 multiplier. They told me that they bench test each completed unit prior to shipping to ensure that it’ll deliver. About 90% of the posts I’ve seen from STEP users claim the unit ran at the prescribed speed right out of the box at the normal voltage settings.

Q. Is there any need to be concerned about condensation from peltier-cooled cpus?

A. From what I’ve read, and in the email exchanges I’ve had with people using them, I would suggest that the possibility of condensation is something to be aware, but if a system is set up properly the condensation factor is often negated by a combination of a good heat sink, good fans and system circulation, and lastly… operation in a room that does not have an extraordinarily high amount of humidity. To some degree, the heat of the cpu and the system will take care of drying some of the air inside the chassis.

Q. What’s the real scoop on PC100 Memory?

A. If you intend to run an OC’d system, it probably makes sense to consider quality memory that will support your current and future needs. For instance, most guys have said that with the “right” CPU (Celeron or PII) and fairly generic PC100 memory, you should be able to overclock. If you intend to go to the 100MHz speeds, then perhaps it starts making sense to consider what your motherboard might support down the road (112, 124, & 133MHz) and look into higher performance SIMMs.

Q. Are there any basic guidelines for PC100 memory selection?

A. Here are a few general guidelines that might help sort out some memory issues:

"Observations of a Would-Be PII Overclocker"

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Group A – SIMMS using these chips are supposed to be capable of 133MHz speeds.

Manufacturer Chip Part Numbers
Samsung CAS2 KM48S8030BT -GH
Samsung CAS3 -G8
NEC CAS2 D456841G5
LGS (tAA=16ns) GM72V66841CT -7J

Group B – SIMMs using these chips are supposed to be capable of 124MHz speeds.
Manufacturer Chip Part Numbers

Manufacturer Chip Part Numbers
Toshiba 8ns CAS3 -80H
Mitsubishi 8ns M5M4V64S30ATP -8
LGS (Goldstar) LG8

Q. Which video card would be the best for a OC’d system?

A. If you are a gamer who wants great 3D, it probably makes sense to look at the various TnT cards that are out there from companies like STB, Diamond, and others. If you are more interested in 2D applications like photoshop, corel, or general computing programs, you might be better off with a Matrox product. It also makes sense to ask around various NGs and forums to see which product is most adaptable to a close match of your overclocked system.

Q. What about AGP versus PCI video cards?

A. From what I gather, both will work in a overclocked system, but the edge might go to AGP video cards for some of the extreme overclocked systems. Then again, some cards will adapt better to working in an overclocked system and also some video cards are overclockable themselves.

Feel free to copy this information and use it as a reference. All I ask is that you leave in the credits and copyright info. Thanks!

© 1998 Mike Langieri

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