Should declare itself.

More interposers??? Sphere478 must have put you up to this 😁

The modem was fitted as I saw it and thought it would be interesting, also I have some old line equipment to play with hence the modem, and was playing around dialing up a friends computer over the landline.

The Mr. Bios should have a lot more features than the stock bios, also never had an opportunity to get one back in the day, had a friend who got one on their 386 and could tinker with cache and timings. Don't know how much it would enhance a 286, but again just making a 286 that I could only have dreamed about when I was younger.

Want to sort out the Simm issue before I start trying to push it to 30mhz, also would like to put a fan/ heat sink on the processor I was going to do that.

Does the 287 CLK board allow for an external clock？

Anonymous Coward wrote on 2022-06-21, 14:17:

Does the 287 CLK board allow for an external clock？

All it does is control the state of pin 39, the clock multiplier. Pin 32 is unaffected

Well cannot escape the discussions on oscillators, stuck a socket on by my maths coprocessor, installed a 60mhz crystal and changed the jumper and the results:

Before - 33.51
After - max 40.00

Would try a 60mhz in the main socket but as previously suggested the socketed memory probably could not take it until I solve the SIMM issue.

Just to cause even more oscillator disruption, noticed there is a slot to put an oscillator on the Adaptec SCSI card...

Well God knows what is going on with the 4MB SIMM's, cleaned the sockets still did not work, cleaned the SIMM edges still no joy, tried multiple types of SIMM and nothing.

I know the sockets work as they accept the 1MB modules. Thought it might be something to do with the jumpers, tried multiple configurations and tace where they went on the board, then all of a sudden it accepted them and started working with 16MB or RAM, very, very strange.

But anyway the jumpers are not setup as I would expected:

JP3: pin 1 -> RN1 pins 3 & 4 pin 2 -> SIMM4 (pin 02) pin 3 -> RN1 pins 7 & 8
JP4: pin 1-> RN3 pins 3 & 4 pin 2 -> SIMM3 (pin 02) pin 3 -> RN3 pins 7 & 8
JP5: pin 1 -> RN2 pins 3 & 4 pin 2 -> SIMM3 (pin 27) pin 3 -> RN2 pins 7 & 8
JP6: pin 1-> RN1 pins 1 & 2 pin 2 -> SIMM2 (pin 28) pin 3 -> RN1 pins 5 &6
JP7: pin 1 -> RN3 pins 1 & 2 pin 2 -> SIMM1 (pin 28) pin 3 -> RN3 pins 5 & 6
JP8: pin 1 -> RN2 pins 1 & 2 pin 2 -> SIMM1 (pin 27) pin 3 -> RN2 pins 5 & 6

Now pin 2 could be connected to more than a single SIMM slot (i.e. possible JP5 is also connected to SIMM4, JP3 is also connected to SIMM3 and JP8 also connected to SIMM2)

Also during testing both SIMM1 and 2 need to be populated to boot, as you would expect expected.

Intresting to note that the common pins are 27 (RAS) and 28 (CASP) which I thought were more to do with the parity side of life and pin 2 is the CAS so latency, any ideas?

out of curiosity...

How are the jumpers now set, so you have working 16MB, ie 4MB simm supported ?
and any id on RN1, RN2 and RN3 ? I'd expect some connection to the chipset for those, either directly or via a buffer chip.

Feels like cold joint somewhere if things are coming and going like that.

pshipkov wrote on 2022-06-27, 15:52:

Feels like cold joint somewhere if things are coming and going like that.

Thought that and continuity tested everything and everything is good, also if I immediately take the 4mb simm out immediately and replace it with a 1mb module it works, it is just 4mb modules it has issues with.

But is working solidly at the moment with 16mb in, bizarre.

Another curve ball since removing the dram and having 16mb in, the EMS driver does not work now, but that is not really a deal breaker

weedeewee wrote on 2022-06-27, 15:19:

out of curiosity...

How are the jumpers now set, so you have working 16MB, ie 4MB simm supported ?
and any id on RN1, RN2 and RN3 ? I'd expect some connection to the chipset for those, either directly or via a buffer chip.

Yes, 16mb with 4mb simms.

All jumpers are shorting pins 2 and 3 at present, need to do a bit more testing to see where the circuit leads after Resistor Networks, 1, 2 and 3.

Quick update, noticed the system will freeze randomly usually during heavy disk activity, suspected it to be the fancard using the CF card.

Tried a burn in test using PC Diagnostics '95 and sure enough it stopped on disk access on the 25th ish run.

Swapped it for a PT-606E and left it running most of the evening, no crashes stopped testing at the 136 run throughs of the test.

What is a "fancard"

An IO card with two fans

Ahh yeah I've had spotty results with those UMC multi IO cards on early motherboards

Fancard your chance to blow hot air around in your case

Gotta wonder what the point was unless it could ventilate outside

The fans seem to blow into two different directions, also.. 🙂

snake oil is also not made out of snakes but lets not get lost in details.

The fancard was installed as I thought it looked different rather than cooling, the fact it blew air straight onto the SCA SCSI drive was a little bonus. Anyway think the fan directions are part of the design, found this on a auction site:

Anyway back to the job in hand, mostly been playing with software and playing around on how I want the hard drive partitions set up on the 286.

However, also installed the extra 1mb RAM on the video card and again it did not recognise it, so installed the capacitors next to the banks, and passed continuity testing confirming they are likely required, but that did not work.

The extra RAM is connected to ET4000 confirmed through continuity testing.

There is a spot for a PAL chip (PAL16L8) so might install a socket and install a chip, now if that does not work there is only left spots for resistors and a VRM, but I have no clues of their values. I could a least see what the other capacitors are (100nF) to install the correct ones and the spot for the PAL chip states PAL16L8.

Edit: I am aware this probably will not work but I want to try anyway in the interest of experimenting, also I am confused why they would put the sockets on there for the extra RAM if it was not possible to upgrade the card, seems a bit of extra wasted money in the production process if they do not work.