Uncreative Labs

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

I bought one of these chips recently. I am wondering what makes the 287XL+ different than a regular Cyrix 287XL. Since the Cyrix 287s are infact based around the 387 core, I am guessing that the differences would be similar between a Cyrix 387 and 387+. However, I am not sure what makes the 387+ so special either. Any Cyrix gurus in here?

Joined: 19 Apr 2006 Posts: 261 Location: WisConSin

This isn't for cyrix but the IIt documentation I have laying around said that the 486slc required a plus type chip to operate reliably, the non plus chip had timing issues with slc chips. I can't figure how that would make any difference on a 287 though unless a 287xl+ works on a 386sx as well as a 286.

On this subject what the heck is a Cyrix 2x86 and a 3x86 ?? Long ago I wanted to buy a pair listed but the price wasn't right for curiosity.

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

Hmm...you might just be right about that. The 287XL is meant to be installed on a 286 motherboard, but in theory it should work in a 386SX(and 486SLC) as well, provided there is a socket. The 287XL is really a 387SX in 40pin DIP packaging. Though, I have been unable to get my Intel 287XL working with my 486SLC upgrade module, I am hoping things will be different with the Cyrix.

Also, there is no such thing as a 2x86 or 3x86. Somebody just made it up. Cyrix's first CPU was a 486DLC/SLC. They never made 286 or 386 chips.

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

Well, I guess none of this matters anymore, because as it turns out my 287XL+ is a Chinese fake. I guess somebody was hoping to get rich selling these to CPU collectors or something, because a lot of people in the CPU-forums got screwed like I did. thankfully most of the sellers of these chips took them back. I exchanged mine for a second intel 387DX.

Joined: 22 Apr 2007 Posts: 264 Location: Ohio/USA

Is it a fake non working (empty) chip, or did they just use a different chip and change the markings?

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

It seems that they used a different chip, because installing it causes the system not to boot. About five different people tested it in their machines, and they all got the same result.