Severe Interoperability Problems with Intel Chipsets: How to Fry Your i845 Motherboard

By Van Smith

Date: October 29, 2001

UPDATE: We follow-up with important news about the "Pin A2" test.

We were merrily completing our new Intel i845-based 1.8 GHz Pentium 4 test system when we flipped the switch on the power supply and the system came on instantly -- which should not have happened.  Too late.  The smell of ozone was already wafting in the air, turning our stomachs.  Our new i845 system was dead.

Why did this happen?  Sometimes motherboards are simply bad.  There was no evident physical damage to this one, the FIC VC11, but we would not rule this possibility out.

The FIC VC11: note how tiny the Socket-478 is compared with its heat sink mount.

Another concern was the gargantuan-but-stock (this is the cooling solution included with boxed P4s) Intel Pentium 4 heat sink.  This CPU cooler has a retaining mechanism that applies so much pressure to the microprocessor surface that the motherboard is visibly deformed.  When the clamps are engaged, underneath the miniscule Socket-478, the motherboard bows out by perhaps 1/8".  We could not rule out that the motherboard had been damaged by this huge amount of pressure necessary, apparently, to ensure that the little-chip-with-a-huge-die doesn't overheat.

The monster stock Pentium 4 CPU cooler compared to a typical VIA C3 CPU cooler.

But, then a thought occurred to us.  We had heard that certain AGP cards would not just fail to work in i845 motherboards, but that using them could also fry both the motherboard and the graphics card.  The idea that the Intel i845 could have such an egregious flaw that it would self destruct if used with our new Hercules 3D Prophet 4500 never crossed our minds -- until now.

The Hercules 3D Prophet

We consulted the excellent article on the German site HardTecsForU to find out which pin on AGP 4X cards we needed to use to determine if the they were i845-killers or not.  The test was simple: just take continuity checks for pin A2.  If this pin is connected to ground, then the video card should not fry the i845.  If pin A2 did not go to ground, then the video card and the i845 motherboard would embrace in a death tango.

We removed our brand new Hercules 3D Prophet 4500 and made the measurements and our stomachs fell.  Open.  The circuit from pin A2 to ground was open.

Oh, no!  Pin A2 does not connect to ground!

After we recovered ourselves from the distressing realization that the Intel i845 likely died from its lack of interoperability with our video card, we decided to quickly scan through a number of AGP 4X video cards we had on hand for the same condition.

Below is a table showing which graphics cards we tested that had pin A2 routed to ground and those cards that did not.  Although we cannot guarantee that cards listed in the "Good" column will actually not fry your i845 (and, reportedly, the i850), they at least meet the initial compatibility requirements.

Good (Shouldn't fry i845) Bad (Might fry i845)
Vision Tek GeForce3 P50 Diamond Stealth III s540 Extreme
3Dlabs Oxygen ATI Rage Fury Maxx - Rage 128 pro
ATI Rage 128 pro Elsa Erazor III (100 ohms)
ATI Radeon 32MB DDR Hercules 3D Prophet 4500
Elsa Synergy III SIS 305 32MB
Hercules 3D Prophet 4000xt Diamond Viper II z200 Savage 2000
Jaton 3DForce G-32 (Trident Blade T64) Diamond Viper v770
MSI Starforce 820 32 MB geForce 2GTS VideoLogic Vivid! XS (Kyro II)
Matrox Millenium G550  
Matrox Millenium G400 32MB  
Matrox Millenium G4500 16MB  
ASUS AGP-V3800/32MB  
nVidia TNT2 Model64 32MB  
ELSA Erazor III A32  
Guillemot Maxi Gamer Cougar  
Guillemont 32MB GeForce DDR   

Fortunately the Hercules video card continued to work in other motherboards, but the VC11 was dead.  This underscores the severity of the AGP interoperability issue plaguing Intel i845 (and, reportedly, i850) chipsets. 

With the high percentage of AGP video cards demonstrating this fatal incompatibility, we view Intel chipsets with this interoperability problem, the i845 and the i850, severely flawed.  If a Pentium 4 platform is a necessity, we strongly suggest that buyers look elsewhere for reliable core logic solutions.


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