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rmjay
November 8th, 2017, 12:10 PM
Hi all,

I recently got a 286 machine, it has a 12 MHz CPU and 2MB of RAM, and I was curious if I could upgrade the CPU to a CS80C286-25 chip. The only crystal I could find on the motherboard says "ACETCH 14.31818 MHZ" on it. The motherboard itself is unknown, the only thing I could find was a "160G" on it.

Thanks

Caluser2000
November 8th, 2017, 12:15 PM
Is this close to it? http://stason.org/TULARC/pc/motherboards/U/UNIDENTIFIED-286-ELT-286B-160G.html

rmjay
November 8th, 2017, 12:22 PM
Not really, my board has both BIOS chips by an 8-bit ISA slot, and has room for both IC and SIPP based RAM. I have included some pictures.4185241852418534185441855

krebizfan
November 8th, 2017, 12:23 PM
Maybe provide a picture of the motherboard and a description of which BIOS is being used. There is almost certainly a documented motherboard very similar to the one you have.

Changing the crystal for one that is twice as fast will make the expansion slots twice as fast which means the expansion cards won't work. The high speed upgrades placed the new CPU on a small card with other logic to run it at the increased speed while letting the rest of the system stay at normal speed. Basically, it will be difficult and expensive to get a performance boost and that performance boost will be small because most of the system will still be slow. Enjoy a solid 286 as it is and if you want something 25% to 100% faster, watch for a 386 or 386sx system to show up on the cheap.

Edit: Wow, these threads move fast. Answers provided before I can post questions.

Chuck(G)
November 8th, 2017, 12:37 PM
Look at your 5th photo--see the package with the silkscreen legend, "OSC 1" in the corner of the board? What does the package say? It's a pretty safe bet that that is the CPU clock oscillator (XCO).

rmjay
November 8th, 2017, 12:46 PM
I am going to get into the case in a few hours, I will see if I can get a better photo of it.

rmjay
November 8th, 2017, 04:16 PM
I took a picture of the chip in question. It says 24.0000 MHz on it. I also took a picture of the BIOS on startup.4186141862

SpidersWeb
November 8th, 2017, 05:42 PM
24 divided by 2 is exactly 12Mhz - so that'd be the CPU oscillator. But I don't think replacing that to get a big speed boost is going to be as simple as changing that one part. In my head I'm thinking about other clocks generated by that crystal, the timing design of the motherboard and RAM, etc etc

Personally I'd agree with krebizfan - enjoy it as it is, and use something with more power when you need it.

Anonymous Coward
November 8th, 2017, 06:12 PM
You might be able to squeeze 16MHz out of it. I think 20 or 25MHz is really asking for trouble.

Your best bet for upgrading the CPU is to use a module that multiplies the clock. Make it 486 for example runs with a 2X clock (24MHz) on a board like yours.

BloodyCactus
November 9th, 2017, 08:25 AM
the chipset might not be able to handle the cpu at that clock speed. I know some chipsets were speed grade binned and marked as such but most were not speed grade marked.

DeathAdderSF
November 9th, 2017, 01:22 PM
Your best bet for upgrading the CPU is to use a module that multiplies the clock. Make it 486 for example runs with a 2X clock (24MHz) on a board like yours.

I second this. I've found the Make-it-486 provides a great deal of extra speed to my Tandy 1000 TX.

rmjay
November 9th, 2017, 03:20 PM
I have thought about one of those 386 or 486 upgrades. The only problem is they are rarer then hen's teeth and hugely expensive.

6885P5H
November 9th, 2017, 04:48 PM
My opinion is that you should really remove that barrel battery from the board. It's not a Varta but that doesn't mean it's harmless. All barrel batteries should be removed or be under strict supervision. Remove it by unsoldering the tabs from the board, be careful not to put your iron on the contacts too long to avoid rupturing the battery. Or you can cut it off. I've lost a board to one of those batteries, it's serious stuff.

I looked up Make-it 486 on Google. It doesn't look rare but if it is that really sucks. Unfortunately sellers are free to scam anyone they want. If you don't like the price don't buy it but sometimes that is impossible. You can thank recycle-happy people, propaganda, and the lack of effort by world leaders to stop the electronic heritage genocide for that.

krebizfan
November 9th, 2017, 05:24 PM
Given the size of Transera (the company that owned the Improve Technologies line including Make-it 486!), there could not have been more than a few hundred thousand Make-its made. It will be much rarer than regular 486 systems.

DeathAdderSF
November 9th, 2017, 06:10 PM
I have thought about one of those 386 or 486 upgrades. The only problem is they are rarer then hen's teeth and hugely expensive.

Be patient yet vigilant. I was able to buy two Make-it-486 CPUs from eBay this year, in the span of only a few months, each for a fair price.

rmjay
November 9th, 2017, 08:31 PM
How dangerous are barrel batteries really? I mean, besides leaking and wrecking things.

6885P5H
November 9th, 2017, 11:21 PM
A few hundred thousands is a TON of products made. I know many PCs that had production runs infinitely smaller than that. Some PCs are rumored to have been made in the 2 or 3-digit numbers. And the fact that they don't exist anymore seems to prove that.

I don't think they're any more dangerous than your typical alkaline battery. If you touch a leaking one, it gives this indescribable feeling in your skin just like any other battery. The usual stuff. The danger here is that it may look fine now, but in a month it could have already started spreading its corruption and eating the board.

GiGaBiTe
November 9th, 2017, 11:56 PM
How dangerous are barrel batteries really? I mean, besides leaking and wrecking things.

They're NiCD batteries and contain cadmium, which causes all sorts of lovely health effects like cancer, renal failure and lung damage among other things. Though this assumes you ingest said cadmium.