Cyrix Media GXm-300GP 2.9V. Real or fake?

[feipoa]

What do you think, the real deal?

[Mixeur]

the real fake

[feipoa]

Why do you think its fake?

[Marcin]

[feipoa]

I also thought it looked genuine. I haven't come across a -300 which looked genuine before. I'm planning on testing it to determine if it is genuine. I know my -266 chips won't run at 300 MHz.

[CPUShack]

Looks ok to me, thats made in Nationals R/D fab in Santa Clara

R3JE28???

R = Santa Clara
3 = Rev 3.x (first National version)
J = Assembly location, which I havent seen used before
E2 = Lot #

[feipoa]

Interesting. So these were indeed fabricated?

Anyone ever see the -300 in a motherboard?

[Mixeur]

[adamajer]

Looks genuine to me, go one in my "not so well organised" collection, I'll dig it out and take some pics

[feipoa]

Did you find your chip?

[CPUShack]

There certainly are a lot of fake ones out
By far the 'best' fake one I saw was made from a Pentium 75 LOL

[feipoa]

Why do you suppose that is? Is this a high dollar yield collectors chip?

[Neology]

I don't think it is fake for the collection perspective.

It is more likely to be faked two decades ago, selling more expensive for use.

[feipoa]

This came in the mail today. Think it will work at 300 MHz?

There is an ominous warning in the GXm databook,

[feipoa]

I have tested the GXm-300. It works fine at 266 MHz, but at 300 MHz, I can only get it to boot into DOS, not windows, nor run DOS Quake stable. Same problem if I use the SDRAM divide by 4 and only install 64 MB. The chip doesn't get hot at all. I suspect the issue may be related to the current draw and that the onboard VRM may not be able to cope. I'd have to look up the datasheet to confirm this, but...

When I use a GX1-300P chip, which I think is also quite rare in the PGA flavour, I am able to boot into Windows at 300 MHz. This chip, though, is a 2.0 V chip and I'm running it at 2.1 V. So perhaps I could try to undervolt the GXm-300. I've already tried running it at 3.1 V.