FYI Possible AMD A64 Memory Controler issue discovered

[imported_Aelius]

It appears that some people while trying to overclock their RAM on A64 CPUs have hit a brick wall at aprox 220FSB with the RAM. Beyond that it becomes unstable if it boots at all.

This appears to be an issue with certain batches of CPUs but it appears to effect both Clawhammer and Newcastle cores. It's not clear yet if it effects both C0 and CG stepping.

EDIT: Note that it effects most kinds of RAM and it's not specific to one certain brand. It's more likely to be the chips used in the RAM like Micron or Hynix. In fact this is also effecting the OCZ EB line of RAM that uses the Micron chips that overclock very well on A64.

EDIT: You can find out what CPU stepping you got by looking here.

EDIT: The CPU stepping may not be enough to tell you if you are effected or not. You may have to look at the batch and that's only listed on the CPU box or on the heat spreader of the CPU. Look at the 2 lines below the first one. The first one is the stepping.

 

[ItTheCow]

Do you have more details? This would affect me, and I do have problems overclocking...

 

[iwantanewcomputer]

do you have a link to a story or anything? other posts on this problem would be nice too

I had this problem and all the advise i got said to rma my memory, mainly cause it would fail memtest 86 at speeds over 219 which pissed me off cause it was supposed to be good up to 233. once i rmad it and it didn't work i knew it was cpu or mobo but i couldn't just start rmaing until it worked so i'm currently running at 235 ht with my memory on 5:4 which is a total waste

Anybody know if amd is accepting rma's for this problem?

Edit... cow, you probly only have this problem if you can overclock everything fine except for your ram not going above 220 range

If i set my ram to 5:4, 4:3 etc i can get my htt up to about 240 cause i don't have an agp/pci lock and i can get my processor stable at 10x that max htt when it's cool out

you have no idea how hard it has been to find out why my overclocks aren't stable cause this post is all i've seen related to this problem

 

[imported_Aelius]

I found the issue on the OCZ support forum. Found here.

There's a bunch of threads on it so I won't link just one.

Keep in mind that PC3200 RAM might not overclock well (depends on a lot) and it may have squat to do with the memory controler. It could very well be the RAM.

However those types of RAM that are known to overclock very well and you have already troubleshooted that it wasn't heat, RAM, or motherboard related then it's more than likely the CPU memory controler.

You can check to see if it's the RAM by simply using one stick at a time and try each RAM bank, not just one.

If it works with one bank but not others then it's probably the motherboard. If one stick works but the other doesn't then obviously it's the RAM.

This is all assuming heat isn't an issue and that's for you to determine.

If after all that you are still getting piss poor RAM performance then it might be the CPU memory controler.

EDIT: Also it's not clear if AMD is going to accept RMA for this. OCZ for example will help you try to determine the issue. OCZ is in contact with AMD to try to figure out if there is a workaround or if anything can be done. It may only be a certain CPU stepping or it may be certain batches of a certain stepping. Either way once you determine that it's probably the CPU memory controler you should post on their forum and tell them the stepping and batch of your CPU. You can likely find that on the box the CPU came with or on the CPU heat spreader itself.

 

[Dman877]

ROFL, why on earth would amd accept rma's? their cpu's are uspposed to work at 200 mhz fsb and they all do.

 

[Bateluer]

Originally posted by: Dman877
ROFL, why on earth would amd accept rma's? their cpu's are uspposed to work at 200 mhz fsb and they all do.

Exactly, they function as advertised. If I was AMD, I'd would RMA an A64 on the basis that it didn't OC as well as I'd hoped.

 

[Duvie]

Good info.... I remember this short of 220fsb wall for quite awhile now....

How did some guys like Markfw800 and Shimmishim resolve this cause if I remember they seem to get much higher then 220??? Excuse me for my ignorance on AMD64 memory controllers but there is no ratio to work around this and get higher fsb just not as high memory speeds???

 

[BW86]

hrmmm i got over 220fsb at 1:1, guess it doesnt effect mine

 

[iwantanewcomputer]

Originally posted by: Duvie
Good info.... I remember this short of 220fsb wall for quite awhile now....

How did some guys like Markfw800 and Shimmishim resolve this cause if I remember they seem to get much higher then 220??? Excuse me for my ignorance on AMD64 memory controllers but there is no ratio to work around this and get higher fsb just not as high memory speeds???

it only affects certain batches and steppings... i have a C0 newcastle and it has the problem

the best way to tell if it is the memory or something else is to test it in a different system. I had my brother test it in his p4c with abit something mobo and it got up to 254 MHZ at 1:1. a bit different than my 219

i asked about the rma possibility cause i did'nt know if amd cared what the htt was set at as long as the processor ran at it's specified speed. I was thinking they might be fine with you upping the htt and loweing the multiplier and still cover this.

 

[imported_Aelius]

Well I wouldn't laugh at the prospect of an RMA. It is a fault found in the memory controler of some batches and not others. It may have nothing to do with quality control and more to do with the revision of cores that sometimes change week to week and is not advertised.

That's partly why they want to know which batch your CPU is so they can track down the cause.

It may very well be a quality control issue but it's odd that it happens one week and not another. That's why some suspect that it's the revision of the CPU.

I'll be getting my CPU sometime next week. It's an A64 3500 so it's a CG stepping. Will have to see how it performs with my RAM.

I'll be pissed if it's stuck at around 220FSB because the RAM can do 270-280FSB no problem. Assuming the RAM isn't faulty. I'll have to troubleshoot once everything I ordered comes in.

 

[StealthElephant]

Originally posted by: Aelius
It's an A64 3500 so it's a CG stepping.

Sorry to jump in, but are all the S939 CPUs CG stepping?

 

[glugglug]

3500+ CG stepping here.

500MHz RAM.

Unstable with HT overclocked past about 215. Freezes immediately going from 225 to 226.

Motherboard BIOS RAM speed selections are only 133, 166, 200 -- (or 266/333/400 DDR). I guess this is just a control for the multiplier off of the HT bus?

I tried changing to a 4:5 HT and changing to a 9x or 10x CPU multiplier in order to try the higher bus speeds w/o bringing the CPU above 2.2GHz and it still would fail to boot (and require NVRAM reset) past 225.

 

[imported_Aelius]

Originally posted by: StealthElephant

Originally posted by: Aelius
It's an A64 3500 so it's a CG stepping.

Sorry to jump in, but are all the S939 CPUs CG stepping?

According to the table I posted with an update in my first post yes they are all CG stepping.

 

[imported_Aelius]

Originally posted by: glugglug
3500+ CG stepping here.

500MHz RAM.

Unstable with HT overclocked past about 215. Freezes immediately going from 225 to 226.

Motherboard BIOS RAM speed selections are only 133, 166, 200 -- (or 266/333/400 DDR). I guess this is just a control for the multiplier off of the HT bus?

I tried changing to a 4:5 HT and changing to a 9x or 10x CPU multiplier in order to try the higher bus speeds w/o bringing the CPU above 2.2GHz and it still would fail to boot (and require NVRAM reset) past 225.

Yeah so you got the shaft. Nice.

Can't wait to find out if I get to be on the bandwagon with my ultra expansive RAM.

 

[Adn4n]

I can easily boot up at fsb 240 at HTx3, but it's not stable with my OCZ PC3500. Even at 220 fsb on 1:1 it's not stable in prime 95, though I see no issues while gaming. I had thought that I simply needed more ram voltage(over 2.7), but this is intriguing.

 

[glugglug]

having a hard time finding another thread or article about this. Anyone have a link?

 

[iwantanewcomputer]

Originally posted by: Aelius
I'll be pissed if it's stuck at around 220FSB because the RAM can do 270-280FSB no problem. Assuming the RAM isn't faulty. I'll have to troubleshoot once everything I ordered comes in.

nice ram, what is it/what timings can you run to get that speed?

it really sucks having payed for more expensive ram and not being able to use it

PS...does anybody else see the ht going a little over 220 if you relax the timings. i got mine to boot at 225 with 6-6-6-12:frown: but not higher.

here's my serial number...i don't know which part tells the batch but its a C0 newcastle 3000+:

9845535A40295

was that OCZ's site where people were posting these numbers?

 

[imported_Aelius]

Originally posted by: iwantanewcomputer

Originally posted by: Aelius
I'll be pissed if it's stuck at around 220FSB because the RAM can do 270-280FSB no problem. Assuming the RAM isn't faulty. I'll have to troubleshoot once everything I ordered comes in.

nice ram, what is it/what timings can you run to get that speed?

it really sucks having payed for more expensive ram and not being able to use it

PS...does anybody else see the ht going a little over 220 if you relax the timings. i got mine to boot at 225 with 6-6-6-12:frown: but not higher.

here's my serial number...i don't know which part tells the batch but its a C0 newcastle 3000+:

9845535A40295

was that OCZ's site where people were posting these numbers?

The OCZ forum is here.

The RAM I got sitting at home is OCZ EL PC4000 Gold Revision 2. @ stock speed and stock voltage of 2.6v it can do timings of 2.5,3,3,8. It can reach 270FSB+ with only around 2.8-2.85v at stock timings.

I never thought the AMD CPU is going to be the one that sinks me after all the precausions I made in researching hardware for over 6 months. I'll keep a finger crossed but with my luck I wouldn't be surprised if I get the shaft too.

 

[Markfw]

Originally posted by: Duvie
Good info.... I remember this short of 220fsb wall for quite awhile now....

How did some guys like Markfw800 and Shimmishim resolve this cause if I remember they seem to get much higher then 220??? Excuse me for my ignorance on AMD64 memory controllers but there is no ratio to work around this and get higher fsb just not as high memory speeds???

I only get to 220. Never got over it. But I figured it was due to video card or SCSI card not liking the hight PCI or AGP speeds (very early motherboard and no PCI/AGP lock)

 

[trinketsummoner]

So is it the FSB speed thats the issue, or the speed of the ram itself? Im running prime stable at 255 x 10, with the ram 5:4 @ 212, 3xHT. My mushkin ran ok 1:1 upto 227, but with no half multis, this is the best way to OC my system according to benches.

One other thing i found out too was running the HT at 4x or 3x made no difference to benches. 5xHT was stable at default speeds, but isnt once you up the FSB a bit, and 4xHT is unstable after 240ish FSB.

At the end of the day, overclocking isnt guarenteed, its the luck of the draw.

 

[glugglug]

Where is a link to one of the threads? I looked at OCZ forum and didn't see anything on this.

 

[CraigRT]

Originally posted by: Dman877
ROFL, why on earth would amd accept rma's? their cpu's are uspposed to work at 200 mhz fsb and they all do.

exactly what i was thinking. retarded idea at best!

 

[iwantanewcomputer]

Originally posted by: trinketsummoner
So is it the FSB speed thats the issue, or the speed of the ram itself? Im running prime stable at 255 x 10, with the ram 5:4 @ 212, 3xHT. My mushkin ran ok 1:1 upto 227, but with no half multis, this is the best way to OC my system according to benches.

One other thing i found out too was running the HT at 4x or 3x made no difference to benches. 5xHT was stable at default speeds, but isnt once you up the FSB a bit, and 4xHT is unstable after 240ish FSB.

At the end of the day, overclocking isnt guarenteed, its the luck of the draw.

It's just the ram speed that matters. no matter what the actual fsb is, setting a divider to keep the ram at 220 should work.

for those of you who are wondering if you will get a bad processor if you buy one now, i bet they have fixed this problem in one of their more recent revisions. i got mine from zipzoomfly in april and it has the problem. when did everyone else with this problem get theirs?

 

[glugglug]

got mine about 3 weeks ago

 

[JBT]

my 3200 CG runs fine at 245 HTT Anything over that and it fails prime under 20 minutes. I am pretty sure it is the motherboard at fault though.