KX7-333 Memory Questions

[KSquared]

That was a fantastic review and answered many questions I had about the KX333. I also liked that it was compared with the KR7A, which was the other board I was thinking of. Very interesting results.
I still have questions about the memory and DIMM slots. From what Abit and the review says, if you want PC2700 unregistered memory the maximum is then 2 GB. If you use unregistered PC2100 memory the maximum is then 3 GB. I thought you could only use 2 slots when it was unregistered PC2700 and 3 slots for unregistered PC2100. (And the only way to use 4 slots was with registered PC2100 memory.) This would mean you had to use only 1 GB chips to get to the memory limits.
But then the review says that they had 4 DIMM slots with unregistered PC2700 (256 mb for total of 1 GB) and it worked fine. Does this mean that you can use any size memory stick of unregistered PC2700 as long as it doesn't exceed 2 GB? Or did the reviewer ignore the Abit rules?
The technicalities of all these boards are beyond me. I am impressed with anyone who can figure them out.

[mdzcpa]

Originally posted by KSquared
That was a fantastic review and answered many questions I had about the KX333. I also liked that it was compared with the KR7A, which was the other board I was thinking of. Very interesting results.
I still have questions about the memory and DIMM slots. From what Abit and the review says, if you want PC2700 unregistered memory the maximum is then 2 GB. If you use unregistered PC2100 memory the maximum is then 3 GB. I thought you could only use 2 slots when it was unregistered PC2700 and 3 slots for unregistered PC2100. (And the only way to use 4 slots was with registered PC2100 memory.) This would mean you had to use only 1 GB chips to get to the memory limits.
But then the review says that they had 4 DIMM slots with unregistered PC2700 (256 mb for total of 1 GB) and it worked fine. Does this mean that you can use any size memory stick of unregistered PC2700 as long as it doesn't exceed 2 GB? Or did the reviewer ignore the Abit rules?
The technicalities of all these boards are beyond me. I am impressed with anyone who can figure them out.

KSquared,

Welcome to the board and thanks for the compliments :)

You are correct about the maximum allowable memory using registered and unregistered memory.

Per Abit, however, there are no slot restrictions per se. So you can use any combination of slots and sizes as long as you do not exceed the limits. Perhaps you may be thinking about the Abit KG7 which required registered memory to be used if filling all 4 DIMMS.

However, that is just the official position of Abit. Unofficially many users have found filling all 4 DIMMS to be troublesome in the past (like on the KR7A). Some had success, some not.

In order to "test" whether using all 4 DIMMS was an issue with the KX7, I populated all 4 DIMMs. I had no troubles to report. I will comment, however, that my maximum overclock was hampered by the use of 4 DIMMs (again, though, this is very common). However, the KX7 had no troubles running the memory at 166mhz with aggressive settings with all DIMMS populated.


I hope this helps.

[dicki]

as allways mdzcpa has covered that perfectly so i will just welcome you to the board :)

[lechumbl]

Hi KSquared,

WELCOME to LiquidNinjas.

Take care........

[KSquared]

Thanks for the welcome guys and also the great information. I figured I found a place with people "in the know." I still do have a couple more question though. Mike says that Abit has no restrictions on the slots to use for the memory. But the Abit site states "supports 6 banks up to 3 GB DRAMs for unbuffered DDR modules," and "supports 8 banks up to 3.5 GB DRAMS for registered DDR modules." It seemed to me that two banks would therefore be one slot? It seems I also read there were two types of memory, single and double sided? Is this true? I will once again appreciate any help with this question.

Kevin.

[Player0]

Hi kevin, yes with SDRAM there are two banks to a slot. So the Abit has 8 banks (4 slots).

There are both double sided and single sided ram yes. The fewer ram modules on a stick of ram, the more stable it generally is (if its a good name brand to start off with). Some manufacturers make more single sided than others, but usually for smaller ramstick sizes (64m/128m). Most ram comes double sided. To the end user, it probably doesnt make much difference.

[Player0]

wow just passed 200 posts :)

[lechumbl]

Jaberwokie!!

[mdzcpa]

KSquared,

Okay...I found what you are looking at. :)

To confirm we are looking at the same thing, check this link HERE (http://www.abit.com.tw/abitweb/webjsp/english/faq_letter.jsp?pDate=2002%2F04%2F23&pQUESTION=Is+there+any+limitation+of+using+DDR%2FS DRAM+modules+on+AT7%2FAT7E%3F) . It is for the AT7, but it applies to the KX7 as well.

And, BTW, it is actually the same limits stated by Abit for the KR7A too, (excluding the PC2700 language).

And your answer, basically, is that Abit is hedging against those who use poor quality memory. My original answer was based on what the KT333 chipset supports versus Abit's FAQ.

Per the KT333 whitepapers, the chipset supports up to 4G of addressable memory. But the maximum DDR memory support is really only about 3.5GB rather than 4GB. This limitation is caused by the PC architecture in which the missing 0.5GB of memory is due to addresses being reserved for PCI I/O space, AGP aperture mapping space and other onboard device I/O space. This limitation applies to all current motherboards and is due to the fact that 32-bit processors can only address a total of 4GB of memory.

Most mobo makers just sacrificed the last half a gig and designed mobos with 3 DIMMS capable of supporting up to 3 gigs of RAM. And all 3 DIMMS were available regardless of registered or unregistered. This is basically just the reference design of the KT333 chipset motherboard.

But, Abit added the 4th DIMM, they had to play with the memory addressing to get it all to work. With high quality memory this is not an issue. But with lower quality memory, which already struggles with memory array features, such as Bank Interleave, there can be problems.

Throw in memory that now runs faster (eg PC2700), and things get even a bit more dicey.

So, although three DIMMS can be used (registered or not) per the KT333 reference design, Abit wants users to "play it safe" and only use 2 DIMMS (4 banks) with PC2700, and 3 DIMMS (6 banks) with PC2100 for unregistered memory.

But you will find this is very restrictive compared to all the other 3 DIMM KT333 mobos out there which claim support equal to that of the KT333 Reference design.

So, the bottom line is that you are technically correct based on the Abit FAQ. And yes, I did ignore that FAQ. But, I guess I didn't think about it because I have been ignoring that suggestion from Abit ever since they added the 4th DIMM beyond VIA's reference design because it is usually just not an issue.

The KT333 can support 3 DIMMS or unregistered memory and the KX7 can too if good memory is used. In addition, the 4th memory slot can be used if the memory is of good enough quality.

So if you want to play it ultra safe or plan on using low end memory, I suggest you follow Abit's FAQ answer re: memory support. But in reality, know that the KR7A, AT7, and KX7 can all easily support 3 DIMMS (and usually 4) when high quality memory is used....after all the KT333 supports it.

One last point you made regarding single sided DIMMS is valid too. If you use only single sided DIMMs, you will only be using 1 bank per stick. So 4 single sided DIMMs would be 4 banks.

Hope this helps and sorry about not understanding what you were asking the first time :).

[KSquared]

Oh my goodness! Your technical knowledge is astounding. This answer then brings up more questions. First, is mixing single and double sided DIMMs allowed? And second, does that mean that you are still technically within the Abit recomendation if you use four single sided DIMMs? How do you know when you order memory if it is single sided or double sided? Can you get a 512mb or 1GB single sided DIMM? And theoretically, could Abit have put six slots on the board for six single sided DIMMs and still get to the 3 GB limit for unregistered memory?

[Player0]

"One last point you made regarding single sided DIMMS is valid too. If you use only single sided DIMMs, you will only be using 1 bank per stick. So 4 single sided DIMMs would be 4 banks. "

Mike, I heard that that wasn't entirely true. That single sided ram could use two address banks. The ram chips sit on one side, and then their leads feed down in to banks 1 and 2 together. I beleive this is generally done on BGA ram, where the modules are high in capacity, but small in size. But I beleive it is up to the manufacturer to decide on this. Using two banks for ram makes the ram more compatable.

KSquared, yes you can mix single sided and double sided. If the ram is only using one bank instead of two, you simply loose access to that bank. With ACPI, power is even disabled to that empty bank.

Again, I wouldnt worry so much about single sided or double sided. As an end user, it doesnt matter to you. Just get high-quality stuff. The motherboard takes care of all the nitty-gritty details. It makes little difference to you if you use single or double sided.

[mdzcpa]

Player0:

Thanks for steppin' in here. Twas a loooong day at work today:(

I would agree that it is not a hard and fast rule about double sided vs single sided DIMMs, but it is a rule of thumb that can still be applied. Checking the specs on the RAM to be considered for purchase is really the best way to tell.

KSquared,

I also follow these general rules of thumb:

The more memory on the stick, the more likelihood of issues. EG Some 512 sticks have more "issues" than 256 sticks. (see below)

Strike a balance between how large each memory stick is and how many DIMMs you want to fill. Sometimes getting bigger sticks a RAM and filling less DIMMs can be better.

Avoid memory modules using x4 (eg. 64Mx4) chips. They are not supported by the KT266A or KT333 chipsets. These are common on 512MB and 1GB DIMMs

Using the above guidelines I always populate the memory array as follows and have great success with all of these configurations on either the KR7A or KX7:

256 megs-
DIMM 1 1 x 256
DIMM 2 empty
DIMM 3 empty
DIMM 4 empty

512 megs-
DIMM 1 1 x 256
DIMM 2 1 x 256
DIMM 3 empty
DIMM 4 empty

768 megs-
DIMM 1 1 x 256
DIMM 2 1 x 256
DIMM 3 1 x 256
DIMM 4 empty

1 gig -
DIMM 1 1 x 512
DIMM 2 1 x 512
DIMM 3 empty
DIMM 4 empty

1.25 gig-
DIMM 1 1 x 512
DIMM 2 1 x 512
DIMM 3 1 x 256
DIMM 4 empty

1.5 gig-
DIMM 1 1 x 512
DIMM 2 1 x 512
DIMM 3 1 x 256
DIMM 4 empty

Above 1.5G I have not tried:)

[KSquared]

And it all began to make sense!
Thanks for all the information, it was very helpful.
Mike, a couple of more questions. How much did it affect the ability to overclock when all 4 slots were filled?
One more somewhat rhetorical question I have is why would anyone use 4 1GB memory in this board, wouldn't they just use 3 1GB memory and put a 512mb memory in the last slot?

Kevin

[mdzcpa]

Originally posted by KSquared
And it all began to make sense!
Thanks for all the information, it was very helpful.
Mike, a couple of more questions. How much did it affect the ability to overclock when all 4 slots were filled?
One more somewhat rhetorical question I have is why would anyone use 4 1GB memory in this board, wouldn't they just use 3 1GB memory and put a 512mb memory in the last slot?

Kevin

When all four slots were filled, the highest FSB I could get to with stability was 179mhz. It would go higher by relaxing all the memory timings, but I did not bother to find that limit as I do not like to run the timings relaxed just for the sake of a higher FSB unless total memory bandwidth improves. I find it best to run the memory agressively, than take up the FSB as high as it will go set that way. The settings used to get 4 256 sticks of to 179mhz was CAS 2, 4 way, 2,5,2, 2T (with 2T being the only concession as a more relaxed setting).

And, no, I would never run 4 1 gig chips.

And BTW, unless your running a workstation of some sort, anything over a one gig total is kind of a waste anyway. IMOHO, 512meg is now the sweet spot between having a good amount of memory, and overclocking. But that's just my opinion. If I were to make a jump from there it would be to 1 gig using 2 512 sticks.

:)