here's a picture of the resistor at R2

fyi resistor is brown red brown gold, 120 ohm. looks like connected to D5, unpopulated, which could've been an led for power indication.

is the underlined ec in cmos checksum failure a photographic glitch or a real artifact?

Edit the title to describe the thread. Will get more views.

Yes. edit the title to "Sunlogix 80386-33/40 (Micro Express Computer) boot loop"
Chips you mention are universal replacement of each other, your board is very much Sunlogix 80386-33/40 (Micro Express Computer) FOREX 386 Cache board doesn't post
Keyboard controller is 99.999% just fine.
Corrosion even if it looks fine at first glance, or you cant see any but battery is dead, will most often screw the keyboard due to proximity. Battery is most likely flat and needs replacement - cut it off the board and look for corroded traces and Vias

take a picture of whole board, looks like yours doesnt have a sticker next to ISA slots and there is real model number there (ends with 401c)

What is the KEY DIAG jumper for ?? Don't think I ever seen that before.....if it is same as in your link to thretroweb picture then it should not be jumped.

Horun wrote on 2022-10-21, 22:18:

What is the KEY DIAG jumper for ?? Don't think I ever seen that before.....if it is same as in your link to thretroweb picture then it should not be jumped.

I have no idea. I have both JP100 and JP101 were not set the same as what The Retro Web shows. I have changed them. In regards to the battery, I have already removed it. upon visual inspection the corrosion still doesn't look too bad, appearing to have tarnished l1 l2 and d200 and r203 areas. I have pictures. Of course B1 where one of the legs of the battery was is corroded and on the second ISA slot from the ram, the 7th pin appears to have corrosion on it. The back of the board looks okay, but I know that looks can be deceiving. I also changed the title of the thread to help out.

here are some additional pictures The only information I have on the board is what is on the silk screen, as seen in the below picture, KM-3401C REV.H3B.

Horun wrote on 2022-10-21, 22:18:

What is the KEY DIAG jumper for ?? Don't think I ever seen that before.....if it is same as in your link to thretroweb picture then it should not be jumped.

I don't know what it was, but once you pointed out that the jumpers weren't set like they show in the jumper guide, I switched them. This is the result. As shown, it's no longer boot looping. I don't know what JP101 and JP100 do, but changing them to mirror what was on TheRetroWeb seems to have resolved the issues. I know this doesn't mean that we are out of the woods yet in regards to possible issues, but this is a step forward. Now I just need to get an I/O controller and some other parts and get to work.

Great ! And the display on monitor looks better than the first picture as mentioned above. Usually the monitor jumper is for: Mono/VGA and Color (CGA) but knowing if jumped is Mono or not jumped is ... can be only found in a manual or trial an error.
Am wondering if the KEY Diag jumper puts the board in some type of odd diag mode and that is why it was reset looping...

Horun wrote on 2022-10-21, 23:32:

Great ! And the display on monitor looks better than the first picture as mentioned above. Usually the monitor jumper is for: Mono/VGA and Color (CGA) but knowing if jumped is Mono or not jumped is ... can be only found in a manual or trial an error.
Am wondering if the KEY Diag jumper puts the board in some type of odd diag mode and that is why it was reset looping...

I wish I knew. Sadly we didn't get into IBM PCs until the 486, so I have very little experience with anything earlier. And you are right that the monitor jumper was for mono or color. switching it now that I have the ability to get into the bios shows that. I also installed a jumper on the battery jumper to set the external battery voltage to 3.6V, but I am curious as to how I should wire a CR2032 holder that. If I remember there is a diode or something that has to be attached to one of the legs to make sure that the battery doesn't try to charge which it can't do?

yay, so the full model number for that Sunlogix board is "KM-3401C". Too bad theretroweb doesnt have an easy way of editing/adding data 😒
yes, KEY Diag is most likely for burn-in testing

You are right about almost no battery damage. I can barely see some dots of moisture? around L1 L2. Pour a dab of vinegar for a couple of seconds, rinse in clean water, dry it and you are done. Accumulator can be replaced by ordinary CR2032 battery plugged into EXT.BATTERY header - it already has diode preventing back charging wired in.

>I also installed a jumper on the battery jumper to set the external battery voltage to 3.6V

what jumper?

rasz_pl wrote on 2022-10-22, 03:44:

>I also installed a jumper on the battery jumper to set the external battery voltage to 3.6V

what jumper?

There is a jumper called JP3 next to the external battery connector labeled as JP4 - It says in the jumper sheet that JP3 if it is open, then the external battery is set to 6.0V and if it's closed the external battery is set to 3.6V

I snipped the table to see if I can show it.

-edit- on the pictures of my board its labeled J200 and in the picture on TheRetroWeb

Now I see it, sorry for stupid question. First time I see a jumper selecting battery voltage.

rasz_pl wrote on 2022-10-22, 07:20:

Now I see it, sorry for stupid question. First time I see a jumper selecting battery voltage.

It wasn't a stupid question. I have never seen a jumper like that either. And I wouldn't have noticed it at all if it hadn't been for Horun pointing out that one of the jumpers was set bad. This led me to find out it wasn't just the one jumper that was set incorrectly to what the guide said, but two. Which caused me to look more carefully at the jumper settings section in the guide. So it was an honest question which for once I had an answer for.

Okay, so here's a question. This board is working. I have a CL-GD5426 ISA card for the video, which is slow, but functional. But I have no I/O card. I know this machine will be limited to 540MB on the hard drive, and I have a mechanical hard drive with that for its size that still works, and I have a CF Card and adapter at 512MB, which is close enough. The question is, aside from being ISA, what is your suggestions for an I/O card? Also, should I get an 80387DX for the board as well? I know that a math co-processor wasn't utilized in a lot of game software, but would it make a difference? Thank you again everyone for all of the help. I am super excited to get this all put together. I have this interesting old AT case I hope to use, and I hope to get my 1.2MB Floppy drive working as well!

Pretty much all IO cards were the same unless you went upmarket to "accelerators" with dedicate cache ram sockets, and those are more trouble than its worth.
There doesnt exist a single 386 game that would use FPU in visibly positive way. You have simcity optional negligent speedup and Falcon 3 "realistic" flight model with broken physics.
The biggest free speedup you can do is find a way of boosting ISA clock speed (bios or crystal).

rasz_pl wrote on 2022-10-28, 04:24:

Pretty much all IO cards were the same unless you went upmarket to "accelerators" with dedicate cache ram sockets, and those are more trouble than its worth.
There doesnt exist a single 386 game that would use FPU in visibly positive way. You have simcity optional negligent speedup and Falcon 3 "realistic" flight model with broken physics.
The biggest free speedup you can do is find a way of boosting ISA clock speed (bios or crystal).

Okay, cool! Thank you for the information. All of the other machines I have that had I/O cards they came with the machine and I have no clue about their quality. There doesn't seem to be any listings that I can see for a 2 IDE and 1 Floppy I/O controller, but the old soundcard I have laying around has an IDE channel on the soundcard.

I thought I would share an update. I got the board into the case I had. Strangely, the 4 brass standoff points only had one that was grounded around the actual hole, so I used vinyl spacers on both the front and the back of the board for the other three. I don't know much about the provenance of this case, the sticker on the front shows it was used for a pentium at some point in the past, but I really like old desktop cases, and this one was originally supposed to be a mini-mid tower set up, but when I got the shipment from the seller on our local friendly auction site, they had shipped an ATX case instead. I shipped that case back to them, and they sent this one instead. It was a bit problematic. It was missing the mount for the power switch. Thankfully with the help of TechAmbrosia, I was able to get a mount that works. I tried printing it in ABS, but the printer fails every time, and I don't know why. But the PLA is working for now, and if I need to, I can print them until the cows come home. What do you think of the case? Does anyone know anything about that logo on the sticker on the front? I have never seen it before, thought it might be a local builder to some region. The case came from New York, if that provides any help in identifying it?

Okay I have gotten everything into the case, and have installed a classic Western Digital Caviar 2540 540MB hard drive and the machine works, but I think I don't have it configured properly. I didn't get an IBM PC style computer until the 486, and our first PC was a 486 from Packard Bell, which meant pretty much no BIOS configuration options as it is. With this machine, the BIOS is overflowing with options, and the Advanced Chipset Setup has options that I have never encountered before and I don't really know how to configure it properly.

BUS Clock Selection: - This has a listing for CLK2IN/4. I'm not 100% certain what CLK2IN is? I looked at the motherboard expecting one of the oscillators on the board to be listed as CLK2IN, but I did not see it. Is this the speed of the CPU, or is it the other clock, which is 14 point something MHz? I recall that the ISA bus was originally designed to run at 4.77MHz and then as things sped up at 6 and 8MHz respectively, but I'm not certain what this should be set to. The CPU is 40MHz, so if CLK2IN is the 40MHz clock, then that sets the ISA at 10MHz, which is probably too high for the low end cards I have in the machine. The options for this is CLK2IN/2, /3, /4, /5, or /6. I thought if it's the CPU speed for the setting the closest I could get it to 8MHz was to do CLK2IN/5, which should be 8MHz.

I/O-RECOVER Control: - I have no idea what this setting is at all and when I tried to google for it, I found nothing? That's really unusual for me, I can usually find something the is referential to what I was intending to search for. Not on this one. It defaults to Disabled, but I don't know if I should enable it or not.

DRAM Access Wait State : - Okay I understand that wait states directly effects that performance of the RAM, but I don't know how to identify which setting I should use. I am using 4x4MB 30 pin parity SIMMS that are 70 Nanoseconds because the 60 Nanosecond ram I had did not pass parity. The options are from 1 W/S to 4 W/S. It defaults to 3 W/S, which is what I have left it at for now as I don't know how to correlate wait states to ram speed.

Adapt. Shadow RAM Cacheable: - I know this has to do with caching shadow ram that is used to block out parts of the High Memory Area to allow addressing for various cards. It defaults to Enabled, and that seems fine to me.

Video Shadow RAM Cacheable: - Again the same as above but specifically for the Video card? It defaults to Enabled, and that seems to work well enough for this junky video card I'm using, A Cirrus Logic CL-GD5426

System Shadow RAM Cacheable: - This one is a little more murky than the others.

Remap Memory: - This is another thing I don't really understand. Is this setting specifically taking memory that should be in the HMA section and mapping it outside of that area to allow for use? It defaults to Enabled, and so I just left it at that.

Remapped Memory Cacheable: - Again not sure what the Remap Memory setting specifically does, but I definitely want it cacheable as that improves performance

Non-Cacheable Block-1 and 2 Size: - I'm not certain what these two settings relate to. They are disabled and I left them as such.

Non-Cacheable Block-1 and 2 Base: - This obviously has something to do with the above heading, but I don't know what it relates to. This defaults to 1024 KB

DRAM RAS Precharge T-cycles: So I remember that RAS is something like Row Access Strobe, and the T listing is the cycle time, I think. This has two settings 2.5T and 3.5T. It defaults to 2.5T and I have left it at that because I know the lower this setting is the faster the ram runs.

I'm sure that the full manual for this motherboard would explain these settings to me but I have no access to the manual. I apologize for bothering everyone here so frequently regarding all of these things, but I very much appreciate the help and support that I get here.