Uncreative Labs

Joined: 27 Jan 2007 Posts: 274 Location: USA

dont ask where in the shop i found one, but i did, the question is what should i do with it? i have one 386 set up that uses the PGA socket but, A, the orig cpu is a 33mhz DX not 25mhx sx ,B, i have a 33mhz math co proccesor, and a 385 cache controller. will it work stableish?

Joined: 02 Oct 2004 Posts: 594 Location: Western NC

Hmm, I thought that one was solely for a 386sx upgrade (isn't it a PLCC?---could be wrong). It'd be interesting to see if it'd work in a 286 though.

Joined: 27 Jan 2007 Posts: 274 Location: USA

well mine is in pga format, so what would i expect if i stuck it in?

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

Hey, that's interesting. I was just playing around with mine the other day. I know a fair bit about this CPU, so I'll tell you what I know.

The TI486SXL chips are fully 32-bit 386DX compatible pinout. There is also a PQFP 16-bit version called TI486SXLC. These chips are pretty much exact clones of the Cyrix cx486DLC/SLC family, but with the notable difference of having 8kb internal L1 cache rather than 1kb. I have done benchmarks of thiis CPU, and the 8kb cache really helps. It makes it almost as fast as a real intel 486 chip.

The performance of this chip is pretty good, but unfortunately it is not the easiest thing in the world to setup correctly. I guess for the best results you should have a motherboard that supports it directly. But, with the control software you should be able to get it going on a regular 386DX motherboard. There are several versions of the control software available, and I have had the best luck with the one meant for the Cyrix 486DRx2 chips. So far the Cyrix control software is the only one I can get to work with my DMA 1542C SCSI controller.

I normally use a non-clock doubled 40MHz TI486SXL chip, but these days I have been trying to get the TI486SXL2 to work also. So far I have not been able to get this chip to work in clock doubled mode. Unlike the Cyrix 486DRx2 chips, these ones do not default to clock doubled mode. As far as I can tell the Cyrix control software does not have an option to enable/disable clock doubled mode (though it may be burried in one of the undocumented registers). In order to gain clock doubled functionality you will need to use the TI control software from either Evergreen REVTO486 or Improve it Technologies Make it 486. I find both of these applications lock up my system though.

So that's where I stand at the moment. The clock doubled mode seems kind of tricky, so you might have better luck just running single clocked at 40MHz.

Does your chip look something like this?

http://sandy55.fc2web.com/ps55/386cpu/makeit486_2.jpg

Joined: 27 Jan 2007 Posts: 274 Location: USA

http://www.chipdb.org/img-texas-instruments-486-sxl2-50-1526.htm

so what should i expect if i replace my 33mhz 386 dx?

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

Is your chip exactly like the one in the photo you sent me? If so, you had better make sure it is a 5V chip before using it. I think many of them were 3.3V models. Most of the SXL2s I see come with a voltage regulator.

Replacing your 33MHz 386 with the TI486SXL2 should give pretty good performance if you can get everything working. By default the L2 cache and clock doubling are disabled. Without the software the chip will only work slightly faster than the 386 it replaced. Most people have problems with the software, so be prepared to do a lot of reading and playing around with settings. Once everything is configured it's generally trouble free.

Joined: 27 Jan 2007 Posts: 274 Location: USA

yea, i got the little board with the voltage regulator, i just need the software, and a reason to use it.

Joined: 03 Feb 2006 Posts: 488 Location: pennsylvanai

every time I see one of those chips, it is soldered on the motherboard
But I have seen boards like that on a piece of circuit board with pins like a regular 386,
I think the IBM version was called Blue Thunder?
and IBM could only sell the chip attached to a motherboard.
most of those mb only had 4 30 pin sockets
and a few also had 8 or 9- 1 meg dips.
so the board has 1m,. 5meg or 4x4+1-17 megs
17 megs was close to the peak for running windows 3.1 or wfwg.
I have a couple of these boards

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

IBM made their own 386/486 hybrid chips, but they were based on Intel cores rather than Cyrix. That's why IBM wasn't allowed to sell their chips separately.

I haven't seen a 486SLC motherboard yet that used DIP RAM, but it really wouldn't surprise me at all. Slapping a 486SLC onto a 286 motherboard must have saved the designers a ton of money.

Joined: 02 Oct 2004 Posts: 594 Location: Western NC

Quote:

Slapping a 486SLC onto a 286 motherboard must have saved the designers a ton of money.

Agreed. But it (the SLC) was a nice little chip for what it did. Essentially a 386sx on speed, it made my PS/2 9553 run Windows 3.1 quite nimbly. Sadly, the 9553 was limited by it's 16-bit MCA bus, so I never could get Win95 to operate in 32-bit mode... Mad

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

I now have TI486SXL2 working properly in clock doubled mode with cache enabled and coprocessor installed. I had to do some goofy things to get this working properly. I used the Cyrix 486DRx2 control software, but instead of using the software frontend I manually programmed the cx486.cfg to configure CCR0 (control register 0) to hex value of 55.

Joined: 27 Jan 2007 Posts: 274 Location: USA

i know its an old topic, but i recently found a cyrix 486drx2 configured for 25/50 mhz. i found out that the TI cpu i had would not fit in the 386 cause the voltage regulater board made the cpu to tall to fit under the drive bay. so, now ive picked up 2 thing, a cyrix 486drx2 @50mhz and a origninal copy of it's make-it 486 software on a 720 floppy. now whats needed to get this thing to work in a computer that uses a 33mhz cpu with math co an the 385 cache controler. and if it works, will it run at the machines speed of 33/66 mhz or the cpu's speed of 25 or will it run at 66 and wear out the cpu fast. ive never dealed with 486 upgrade chips before. and an old compaq beater used for running irc is a little more complex than a regular garden variety clone 386 mobo.

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

Cyrix 486DRx2 and Make It 486 are two different products, so there is a good chance you won't be able to use that software with your chip. What you need is the DRx2 utility diskette. If you look online you can find it for download.

In my experience the 486DRx2 chip is fairly easy to get working in older motherboards. I have the 486SRx2 running with cache enabled in my 1990 386SX without any problems. I found that while TI486SXL performs much better, it generally will only cooperate on boards that specifically support it.

I highly recommend that you not bother trying to overclock the DRx2. I think Cyrix had some production troubles with the 66MHz part, so it's likely that pushing a 50MHz part to 66MHz will result in overheating and instability. I would also like to mention that I'm pretty sure you need use heatsinks on DRx2 chips...yours has one, right?

Joined: 27 Jan 2007 Posts: 274 Location: USA

its got the little green original cyrix heat sink on it. well, i know were i can get a few more of these, but all 50mhz. the last 25mhz 386 i had was back in 05, but the BIOS went belly up, some old quadtel bios.

guess i gota keep my eye open for somethin else...

Posted: Tue Oct 06, 2009 11:13 pm

chip or the whole computer, i might be interested in grabbing one or 2 from you if you can get them