rick12373 wrote:

Might have an ASUS 486 Socket 3 Motherboard PVI-486SP3 soon. So I will not have to deal with Dallas chip anyway! Joy!

I have discovered that these Dallas chips can be replaced quite easily. This seller has loads of them -

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewIt … em=250523279682

The Dallas chip on the Asus mobo is labelled DS12887, but the chips on ebay are marked DS12887A. However, this doesn't matter. I've tested several by removing the DS12887 chip, and replacing them with the DS12887A chip. They all worked. Of course, one day the replacements will go flat. But it's a useful temporary workaround, until it's time to open one up and attempt to replace the battery. IMO, as the replacement chips are cheap, I think it's worth a go. I'll have a go myself, one day..

Hey guys didn't read the whole thread.
It's the first time I'm trying to build a 486 machine and I have some questions.
First of all, I have a lot of RAM from Socket 7 and Slot 1 Pentium 1 and Pentium 2 respectively motherboards. Will it be compatible with a 486 PCI board that I have?
The board is a J-446B with a SIS chipset (can't remember the model number) and I also got an AM486 100Mhz with it. Is it any good? It doesn't have VLB only 3 ( maybe 4) ISA slots and 3 PCI slots.
Also what's the difference between ISA and EISA?
That would be all.
Thanks in regards!

EDIT : Yeah it also has an IDE controller and a floppy controller ( the last one is standard though isn't it?) and the battery isn't like a barrel but the one we typically use from pentium 2 and onwards.

First of all, I have a lot of RAM from Socket 7 and Slot 1 Pentium 1 and Pentium 2 respectively motherboards. Will it be compatible with a 486 PCI board that I have?

SDRAM: absolutely not.
EDO SIMMS: probably not... very few 486 boards supported EDO.

Also what's the difference between ISA and EISA?

EISA is a 32-bit bus that was mostly used in higher-end desktops and servers. It's backwards compatible with ISA, but you can't use an EISA card in an ISA slot. The Wikipedia article gives more detail on it.

Yeah I was talking about EDO.
I might be lucky who knows.
I have 4 MBs and another 8 I think which isn't really good for the tests I want to make.

F2bnp wrote:

The board is a J-446B with a SIS chipset

I did a search for J-446B, and the manual can be found here -

http://motherboards.mbarron.net/models/486pci/j446b.htm

It seems that this mobo can support FPM memory, but not EDO.
I think that some UMC chipset based 486 mobos can support EDO. I have a UMC chipset based "PC-Chips" board with the fake cache, and that supports EDO! (In this instance, you're better off with an SiS board with FPM.)

I just grab 72 pin sticks from may bag-o-72-pin-RAMs and see what works. 😁 If you stick in EDO and the chipset gets scared it will either not POST or it won't get past the BIOS startup.

If you need 30-pin stuff then it's a no brainer really but they need to go in sets of 4 on a 486 mobo.

OK, I have an ASUS 486 Socket 3 Motherboard PVI-486SP3 with an AMD 486 DX4 100 that I am using now. I have two 16MB (TMS417400ADJ-60) ram chips to use. I have being going through the manual which I download and have been checking through all of the jumper settings. I am not sure where I should have my level 2 cache size jumpers set to though. Right now they are set to 256kb. Is this right?

Also, I my CPU is the A80486DX4-100SV8B Revision C. I have been looking at the pin diagram for this CPU (see below) but am having trouble understanding it. What does it mean when the rectangular jumper is hollow? If I do this wrong can I damage the CPU?

hollow means there's no connection (no short). The dark line indicates the pins the jumper shorts. So you place the jumper on the pins the dark lines cross. Considering there's no keying on the diagram (it doesn't say where pin 1 is), the jumper labels on the mobo are probably in the same spot as on the diagram.

If you get it wrong it will mostly likely just not power up, not be stable or be slower than it should be.

What does it mean when the rectangular jumper is hollow?

I think I understood the question differently from swaaye...

If you're talking about the rectangles on JP22 and JP23, it seems to denote optional settings... i.e, the black line on JP23 would be the standard write-back setting, but you could instead put the jumper in the position shown by the hollow rectangle if you wanted to force write-through mode. Likewise on JP22, normally there would be no jumper there, but you could optionally add a jumper at the location of the rectangle in order to force a 2X multiplier. The other settings probably aren't intended for you to screw with, so they're shown as fixed with the black lines.

Thanks for the advice. I am good with computers from the Pentium era onwards. These older boards are not what I am used to.

Does anyone have any advice about my other question?

"OK, I have an ASUS 486 Socket 3 Motherboard PVI-486SP3 with an AMD 486 DX4 100 that I am using now. I have two 16MB (TMS417400ADJ-60) ram chips to use. I have being going through the manual which I download and have been checking through all of the jumper settings. I am not sure where I should have my level 2 cache size jumpers set to though. Right now they are set to 256kb. Is this right?".

Well, the jumper setting depends entirely on how much cache you have. I believe most of those boards had 256KB, therefore the current setting is probably the proper one. If you want to be sure, do a Google search for the numbers on the cache chips to [hopefully, if datasheets are still available] find out the capacity.

swaaye wrote:

.....(it doesn't say where pin 1 is).....

There can be only 1 orientation. If you switch it around, the jumper numpers are backwards 😉

rick12373, if you were to have trouble finding pin 1, it's usually marked on the motherboard with an arrow or a thicker white stripe (hope that makes sence 🤣)
If you find those marks on the motherboard, you could add that to your manual so you don't have to go through finding pin 1 again next time you have to reset the jumpers 😉

Yeah, I thought that 256kb cache was right anyway. I know where pin 1 is by the way on the CPU selector and I now have that right as well.

I have just set the CPU External Clock Selector for 33Mhz. And looking through the rest of the manual it looks like I am done with checking jumper settings. Next step is going to be to put the MB in the case.

I am sure I will have more questions at some point though 😅

get the camera set up before power on so if there are flames you can post a vid for us! 😁

swaaye wrote:

get the camera set up before power on so if there are flames you can post a vid for us! 😁

Actually, that has only happened once to me in the 6 years that I have been repairing and building computers. It was the PSU that time!

I tried making my A7V333 burst in flames once!!11...alas it only emitted a lil smoke 🙁

Yeah well one time I had a HDD power connector plug itself into a internal USB header on the mobo. That was "neat". There was a lot of smoke and some glowing wires. The insulation came off of the wires in about 3 seconds. Poor Abit KT7A. 😳 😮 😁

I was working on a voltage mod for the mobo and so things were a bit messy. PSU is still good to go today though! That was 8 years ago now.

Does it make any difference if I connect my optical drive to primary IDE (as a slave) or secondary IDE as master? I know how it works with newer machines. Was just wondering if it was different with machines from this era.

It's always best to run devices on their own channel if possible.

Are you supposed to use thermal paste on a 486 DX4 100?

Almost ready to switch on for the first time. Get ready to dive for cover! 😳