Getting PC1066 Level Performance from RDRAM & PC800 Motherboards

Getting PC1066 Level Performance from RDRAM & PC800 Motherboards - Page 1

Getting PC1066 Level Performance
From PC800 RDRAM & PC800 Motherboards
A modification project on the Abit TH7II-RAID

By, Dave Altavilla
April 5, 2002

It's been a long time coming but finally, the Pentium 4 platform has gone mainstream enough that motherboard manufacturers, like Abit, are building motherboards with the "Power User" and "Tweaker" in mind.  We've seen a bevy of motherboards recently released for the Pentium 4, with DDR SDRAM chipset from Intel, SiS, and VIA.  However, RDRAM boards, with a few exceptions, have been a little bit more straight forward with fewer bells and whistles than their DDR counterparts.  Regardless, Abit's fantastic TH7II-RAID for the Socket 478 Pentium 4, made quite a splash when it hit the Labs, back in August '01.  It has been an in house favorite ever since.

In the event RDRAM is new to you, the current spec for RDRAM memory is labled "PC800".  That is to say the standard clock frequency for the memory bus is a clock doubled 400MHz speed for a total of 800MHz.  It's a little confusing if you think of the technology versus DDR, which specifies the speed in the name, in bandwidth versus clock speed.  "PC2100" for example runs with only a 266MHz (133MHz DDR) clock but has 2.1GB/sec of bandwidth.  In contrast, PC800 RDRAM boasts 3.2GB/sec of bandwidth.  Now, we've been getting rumblings that Intel is readying a "PC1066" chipset, which has a 533MHz clock doubled memory clock for 1.066GHz and a 133MHz Quad Pumped Front Side Bus at 533MHz.  We can't wait to get our hands on a motherboard based on this chipset. 

Modding the TH7II-RAID for PC1066, or close to it
A "Tweaker's" Socket 478 Dream

Standard Disclaimer:

So, while we're waiting we thought we would show you a few tricks that just might get you in that PC1066 ballpark with your current gear!  Now, I'll add in our general disclaimer here.  This modification is certainly NOT for the novice.  As a matter of fact, we had a very skilled PCB re-work technician help do the de-soldering and soldering on this project.  Her work was impeccable and we would have never attempted this modification without her assistance.  So in short, if you try this you are totally on your own.  It can be done very easily with the help of someone very experienced with a soldering iron and solder wick.  However, you can also toast your board up relatively easy as well, if you don't know what you are doing.  Oh and guess what?  This procedure totally and completely voids any trace of warranty you may have on your mother board.  Go figure eh?

Alrighty then, first we would like to acknowledge one of our very important sources of information, that being a gentleman that goes by the nick of "Raystonn" over at the Vapochill Support Forum.  The folks over there have Pentium 4's overclocking to 3GHz at PC1066, all day long.  Very good info can be found there on this subject.


RDRAM, what is and isn't capable of PC1066:

Obviously, in the absence of true PC1066 memory on the retail market, we have to make due with overclocked PC800 memory and a motherboard that has the ability to overclock the FSB, like the Abit TH7II-RAID for example.  With a 133MHz FSB and a 4X multiplier, you'll be hitting 533MHz SDR and 1.066GHz DDR on the RDRAM clocks.  However, there is a good possibility you'll  need an unlocked Pentium 4 for that because, there are very few chips with standard air cooling, that will hit a 33% overclock, with the exception of the 1.6GHz variety of the Northwood.  This chip is Intel's new overclocking king.  As a result, with our 2.4GHz chip, we had to settle for something a little less but close to PC1066 performance.  When the new 133MHz Northwoods are available, it will be a whole new ballgame and the overclocking community will be having a field day with that CPU, we are sure.

So, back to our RDRAM.  Most of today's standard PC800 Samsung RDRAM will handle PC1066 or a 533MHz clock, as long as you get modules with the lower density RAM chips on them.  These are typically identified as "double sided" or "16 chip" modules, if you are looking at 256MB sticks for example.  Check with your retailer but they are fairly readily available.  Take caution though, some of the newer brand of PC800 RDRAM modules have higher density chips on board that don't overclock well at all.  In addition, it is best to only load up two slots on your motherboard.  With the additional loading of a total of 4 RDRAM slots, the clock jitter causes the heavily overclocked memory get a little flaky.


DRCG - The Direct RAMBUS Clock Generator:

Now, this one is the REAL hurdle you have to overcome, the PC800 DRCG or Direct RAMBUS Clock Generator.  The ICS DRCG that came standard on our TH7II-RAID motherboard, uses a part that is only rated for up 400MHz clock speeds for PC800 specifications.  See if you can spot their location on the board shot here on the right.



Very astute folks!  They are right below the HotHardware logo in that shot.  Actually, those are the new TI DRCGs that we have replaced on the board, that support a 533MHz clock for the full PC1066 standard.  You probably couldn't tell the difference because they are so small. So, we'll magnify things for you a bit.

DRCG Close-ups




TI DRCGs Closeup


However, the ICS DRCGs that come standard on this board, will only handle about 468MHz or 117MHz FSB for overclocking, without getting very flaky with the RDRAM. The T.I. DRCGs (far right) will handle 533MHz or an FSB of 133MHz (or theoretically higher) all day long, because they are designed to support that speed.

Now then, you know that the ICS parts that came standard on our TH7II-RAID, simply had to go.  We're not 100% sure of this but we're fairly confident that almost all DRCGs that are designed to the PC800 or PC1066 specification, have the same lead footprint or pin out with fit, form and functional equivalency.  Take a look below to see the handy-work of our friend the Re-Work Technician!

No matter how hard you look, you can't even see where the solder forms over the pads on the board to make contact with the PCB.  This is professional PCB re-work folks and it is the only way to do this modification.  If you don't have the experience with a soldering iron, don't even think of attempting it.  Also, note the orientation of the chips in this shot.  TI designates the "pin 1" location with the grey stripe that is silk screened on the top of the part.  This way you know you have the pins facing the right way and on the right pads of the PCB.  If you flipped that part around, you might cross your power and ground connections and fry your board but good.

Overclocking at near PC1066 speeds
If only our P4 was unlocked or had a 133MHz FSB!

Here we'll show you the result of our overclocking efforts, with our new DRCGs installed on the TH7II-RAID.  Again, we were unable to hit the full 133MHz Front Side Bus speed that would allow us to overclock the memory to PC1066 levels, due to the fact that our CPU just wouldn't handle it.  However, we were able to overclock our 2.4GHz Pentium 4 faster than we ever could before, with standard air cooling.  We used a Thermaltake Volcano 478 to cool our CPU and this little trick on our P4 Northwood, to get the core voltage up a little higher than the TH7II-RAID allows, to 1.9V.

CPU @ 3GHz

Multimedia @ 3GHz

Memory @ 1GHz RDRAM

Impressive scores for sure, are shown here in the Sandra tests.  We've never seen the memory score break 3K until now.  We've included the PCMark memory score here just for reference.  Now, we know you are all wondering, "was it stable".  Frankly no, not over long periods of testing.  However 2.95GHz with an FSB of 123MHz and an RDRAM clock of 984MHz, certainly was!

Again, this was just a quick look into the world of RDRAM, DRCGs and perhaps a glimpse of what PC1066 will bring to the Pentium 4.  Stay tuned to HotHardware in the coming months, to see the real MacCoy when we get official PC1066 modules in house along with Pentium 4s and motherboards that support them!


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