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Modding The Barton XP To A Barton MP
Dr. Jackie Lee writes "Don't have the budget for an AMD Opteron? There's always a cheaper alternative with AMD's current Barton processors. In this article, we'll show you how to run these new Barton XP processors in SMP mode."
Personally, I'm holding out for a mod that lets me turn my Barton XP into a Barton GP, because I really want to buy that next armor class.
Erik
YOU ARE SAYING IMPUDENCE TO ME! THAT IS IMPUDENCE!
It's not really myth - in fact, when you own one of these big IBM machines (zSeries, pSeries), you can call IBM and buy the unlock code for the additional CPUs that are inside your machine but deactivated/locked. You can also only unlock it for a day or a month.
A monkey is doing the real work for me.
Or, maybe, its for those of us who can't afford the hugely expensive 'multiprocessor' chips, but would still like to be able to run a dual-processor system.
As a programmer, it's always a good idea to have access to a dual-processor system, because there are all sorts of lockups that just wont happen on a single-processor system, but will lock your program up on a multi-processor one. Having a hugely expensive system just to debug an application isn't feasible - if you're able to fool a 'single processor' chip into thinking it's a 'multiprocessor' one, then you've got an essential debugging machine at a fraction of the price
What We Know Thus Far
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More than a year ago, we reported a hack which you can apply to current Athlon XP processors to enable them to operate as Athlon MP processors. The hack was fairly simple and it involved connecting a certain trace on the Athlon XP processor to allow motherboards to recognize them as an Athlon MP. The trace has been cut in the factory so it's just a matter of connecting them via soldering (if you're brave enough), or just putting conductive paint on them.
The response we received from fellow users were phenomenal and from what we know, many have tried the hack. Although most were successful, some were not that lucky. Here are a few reasons which we can offer at this point in time
# You'll need to ensure both processors are properly modded so that the motherboard can successfully detect and operate the processors in SMP mode. Clean the contacts with acetone or isopropyl alcohol before applying the conductive paint.
# Certain motherboards would only work with the hack since certain users reported that they were unable to get their SMP setup running even though the processors have been properly modded.
# Only certain BIOS versions would allow the board to run in SMP mode. For example, we tested the hack on MSI's K7D Master which had no problems working with BIOS version 1.3 and 1.4B3. Newer BIOS versions somehow did not allow us to run the processors in dual mode even though the processors have already been physically modified.
After our first article, a lot of emails came pouring in and most users were asking if the hack could be achieved with a Thoroughbred core since our initial article was based on the Palomino core. Well, of course it would and we'll be showing some results with a dual Thoroughbred-B core in the later pages. What we've done here is taking another step further with the Barton core. What's interesting with the Barton is that it's now featuring a huge 512KB L2 cache running at full speed. Get a pair of that running in SMP mode, and you'll get a pretty decent workstation-class system going at a really affordable price.
Now, I'm sure most of you are interested to get your hands on a dual processor system based on two Athlon XP 2800+ (Barton). Find out how you can do that in the next few pages.
Modding the Barton Core
The process in modding the Barton core is just about the same as what we've done with the Palomino in previous articles. All you need to do is just to connect the rightmost bridge in the L5 row. That should probably get the processor detected and running in dual mode. However, that's not the end of the story yet as you'll still need to modify a couple of things on the processor to get it running up to speed.
We know that all the Barton cores are made for 333MHz FSB systems and their multipliers were set to run at its predefined frequency. If you put a Barton processor in older motherboards supporting up to 266MHz FSB, you'll probably get a severely underclocked processor and that's probably what will happen if you have the Barton XP running in an AMD 760MPX motherboard.
Naturally, the next logical step is to modify the Barton XP's multiplier. Since most server boards based on the AMD 760MPX chipset has no multiplier adjustments for anything more than 12.5x (at least for the MSI K7D Master), we'll have no choice but to hardwire the multipliers ourselves. OK, here are a few rules which we should observe
# The default frequency of the Barton XP 2800+ is only 2.083GHz (12.5 x 166MHz), so we should try to target a multiplier with a lower resulting frequency at 133MHz (266MHz DDR) FSB. It should at least ensure that your processor will boot-up after the modification. Since there aren't any 15.5x multiplier allocated for the Athlon XP/MP core, we have chosen to hardwire the multiplier to 15x on both the chips.
# Since the Barton cores come with more transistors allocated for the larger 512KB L2 cache, we should see an increase in power consum
Karma: Bad. (As in Good?)
An Athlon MP costs about $40 more than the equivilent MP. You can buy an older ( 1.5Ghz, fine for testing) SMP-capable proc for next to nothing. Developers don't want a modded version of the top-of-the-line AMD chip just to test their threading.
It's hard to be religious when certain people are never incinerated by bolts of lightning.
why SMP nowadays?
Sadly, there's still a lot of dog-slow apps. Example: ask Macromedia Dreamweaver MX to test a stored procedure with a hundred parameters, and it'll freeze for 30-90 seconds on all of the P4's I've tried it on, pegging the CPU at 100%. On dual-CPU boxes, that means you can still be productive with the other CPU, and do things like whine on Macromedia user groups while it runs.
SMP also helps a lot if your box is both a testbed and a design system: mine runs SQL Server, IIS, and I do my design on it, so while I'm working, there's a ton of processes running.
Don't get me wrong, I still buy the "real" SMP systems with warranties, but just pointing out why I'm doing it, and I'm not rendering.
What's your damage, Heather?
Guess what? You can't guarantee they'll work - people on LKML have refused to help users who have done this, as it simply makes it impossible to determine whether problems are the fault of the kernel or of the CPU itself.
Bah. You don't know anything for sure, neither to these LKML people. They're just trying to eliminate unknow quantities from their debugging (not like I blame them). For all we know right now (being that the article is slashdotted) there is no difference between the XP and MP except a jumper setting. I honestly wouldn't be suprised if it's true. Why go through all the trouble to fab seperate chips when you can just use external jumpers?
This wouldn't be the first time someone could upgrade their hardware by connecting two contacts.
What really matters is determining if there is any actual difference between an XP and an MP. If there is none, then this isn't just for "the overclockers who couldn't care less about stability". There are plenty of others who would love to save $40/cpu.
Since you don't know either way. You're not really contributing much to the discussion. Yeah, without any testing I wouldn't use a modded chip for critical data, but it's not impossible to verify whether or not the modded chip is stable. "it simply makes it impossible to determine whether problems are the fault of the kernel or of the CPU itself" No, it doesn't. There's a simple solution. Test with both modded XPs and regular MPs.
What needs to happen is testing. Without that, we don't really know how useful this mod will be.
Life is too short to proofread.