Those trident cards use the -12V rail in the current reference circuit to the DAC. Are you sure that rail is present on your backplane?

Those Tridents will also fire up in mono (green only as luminance) mode if the VGA connector isn't snug or is dirty... or if it doesn't like the monitor... (Single neuron of it's detection circuit going "Dunno, looks sus" )

Yeah am Curious what backplane are you using ? Did you move M1 jumpers to 2-3 or were they already moved there ?
Other than having 3 ROM/RAM sockets it appears as a standard SBC.
Per the advise on the Trident video agree: Most older SBC (thinking of the Protech and Mitacs) with onboard video use a Cirrus Logic chipset, I suggest using a Cirrus chipped ISA card or an Oak if you have one...

Thanks for all y'all's help so far! I really appreciate the ideas!

maxtherabbit wrote on 2022-02-11, 01:29:

Those trident cards use the -12V rail in the current reference circuit to the DAC. Are you sure that rail is present on your backplane?

Yep, I've got -12v on this backplane. The card works fine with a different CPU board. (As a side note, before I had a proper power supply, I was supplying the -12v line with a 9v battery and some alligator clips. Works great! The VGA card dims as the battery runs out, but it works at least "down" to -5v. Obviously not doing that any more.)

BitWrangler wrote on 2022-02-11, 02:02:

Those Tridents will also fire up in mono (green only as luminance) mode if the VGA connector isn't snug or is dirty... or if it doesn't like the monitor... (Single neuron of it's detection circuit going "Dunno, looks sus" )

Monitor and cable are ok. The VGA card works with the other processor board.

Horun wrote on 2022-02-11, 02:19:

Yeah am Curious what backplane are you using ? Did you move M1 jumpers to 2-3 or were they already moved there ?
Other than having 3 ROM/RAM sockets it appears as a standard SBC.
Per the advise on the Trident video agree: Most older SBC (thinking of the Protech and Mitacs) with onboard video use a Cirrus Logic chipset, I suggest using a Cirrus chipped ISA card or an Oak if you have one...

I moved the M2 jumpers - for absolutely no good reason. I moved them back with no change. I haven't touched the M1 jumpers. I tried randomly flipping jumpers on or off to see if one of them happened to be a "yes please use video" setting - no luck so far. But that's a wild goose chase.

I am using a KayPro PC backplane - the version without the on-board real-time clock. It's dead simple - sockets and some capacitors and a AT-style power connector.

Unfortunately I don't have another VGA card to test this with. I do have a Mono card that works (with the other processor board) that I can try. I don't have a compatible monitor but I can rig up something that will give me most of the screen on my LCD. I just connect the signals to the VGA input of my VGA-to-HDMI converter and it does the best i can.

But even if that works, it doesn't help me any, because I know the 386 is working - I can get all the way to DOS.

I'm attaching a picture of my ACTUAL video card - maybe I've messed up the jumpers? I've tried a few different settings as best I know with no change.

I've also found some manuals for random 386 SBCs that use an ALI chipset in a wild hope that due to some type of reference design hold-over, the jumper labels match. That's kind of a wild stab in the dark. No luck so far.

Does this trident require 14.3 mhz clock on isa bus? does your SBC produce one?

I dont think the issue is related to the BIOS. If you are able to boot into DOS you can try to initialize the VGA manually:

debug
a
call c000:3
int 20
(enter)
g
q

What happens if you switch to another grpahics mode, i.e. by starting a game?

NoTrueSpaceman wrote on 2022-02-11, 06:33:

Unfortunately I don't have another VGA card to test this with. I do have a Mono card that works (with the other processor board) that I can try. I don't have a compatible monitor but I can rig up something that will give me most of the screen on my LCD. I just connect the signals to the VGA input of my VGA-to-HDMI converter and it does the best i can.

Try with SW4 jumper open on your card. Also, try different slots on the backplane, like having the cards next to each other, or as far apart as possible. Some BIOSes do have a simple video init code if they detect VRAM but for some reason not the BIOS extension (glitches in reads will come up with bad checksum) - but this is mostly for a rudimentary mono text output. So that might be why the card is not initialized but you do get some output.

rasz_pl wrote on 2022-02-11, 07:58:

Does this trident require 14.3 mhz clock on isa bus? does your SBC produce one?

I just checked, and yes - it produces both clocks on the ISA bus. (14.3 and 8.3 in this system)

Deunan wrote on 2022-02-11, 09:58:

Also, try different slots on the backplane, like having the cards next to each other, or as far apart as possible.

Wow! This wasn't the answer but it led there!

I tried some different slots, and suddenly the VGA was working! So I thought, "ok, try and make the problem happen to double check it was the slot." .... And I couldn't reproduce the error. The VGA card worked in every slot, every configuration, adding other cards back or leaving them out. I was flummoxed.

So I thought "well maybe something needed to warm up or who knows" and I started to reassemble the computer. It was in this process I noticed that the video would flicker back off. I thought it could be the backplane shorting out or perhaps some tired sockets, so I started gently mechanically flexing things and poking around while the power was on. The video would flicker on and off but tended to want to work more than not.

Eventually I realized it had to do with the cabling and I landed on the ATX-to-AT power supply adapter. It was something very subtle because just a tiny movement of the cable, of even just individual wires, would cause the problem to manifest with a flicker. I was even able to cause the full repro - If I held the cable just the right way, and power cycled, I saw exactly what I saw in the start - the faint crappy green image. But I could now "fix" it by flexing the cable anywhere in the boot process.

Well my 9 volt battery experiments showed that the VGA card didn't really care about the -12v line in terms of working correctly. It seems to only be part of the analog section. You can vary that voltage all you like and the digital part of the card doesn't seem to care.

So I focused my careful prodding with a plastic spudger to every little wire. I gently pulled and pushed each one to see if it was a loose socket or crimp and ... well I found something obvious. Can you spot the problem?

maxtherabbit wrote on 2022-02-11, 01:29:

Those trident cards use the -12V rail in the current reference circuit to the DAC. Are you sure that rail is present on your backplane?

That was it. It was the -12v line all along. I connected a voltmeter to the -12v line on the bus and I could see the voltage twiddle between -12v and something a few volts above 0 as the symptom flickered on and off.

I could have discovered this with a POST card that had LEDs for each voltage, something I think I'll add soon. I could have also found it by actually measuring the -12v line instead of assuming it was working just because "it was connected" and "it worked in another configuration".

I now can proceed building my swapable CPU x86 machine.

Thank you everyone for your help! What a great forum of folks.

For future folks coming along via google or whatever, here is a photo of my KayPro backplane, as well.

Also I'm seeing some weird artifacts still but I assume that's due to poor grounding or maybe some dodgy RAM on the video card.

My current mystery is now "Why did the floppy drive stop working? The BIOS is configured but the drive doesn't do its boot seek and doesn't show up in DOS...". I'll check everything again - this machine has had a lot of "mess around with the jumpers and cables" so I might have left something in a bad state.

That's just par for the course with trident

At least Tridents are reasonably fast with decent video quality - though I feel having local +- 9V regulators and better filtering would help with DAC noise. How come sound cards had local regulators for DAC but not video cards. Still, it could be worse, it could be a Realtek.

Anyway, kudos to OP for actually testing this properly. Some people would just move the card, see it working now, assume that was the issue. As for missing floppy, is the ribbon connected properly? Don't assume the tab on the connector is in the correct place if it's a Sony drive. Also, are you using a CF card for HDD? Disconnect it, see if the floppy comes back.

I think the kind of noise would generally be in the 10s of kilohertz and lower, which sounds like farts, buzzes and squeals on a soundcard, but doesn't affect mhz level signals much.

NoTrueSpaceman wrote on 2022-02-11, 15:48:

For future folks coming along via google or whatever, here is a photo of my KayPro backplane, as well.
IMG_1375.jpeg

My current mystery is now "Why did the floppy drive stop working? The BIOS is configured but the drive doesn't do its boot seek and doesn't show up in DOS...". I'll check everything again - this machine has had a lot of "mess around with the jumpers and cables" so I might have left something in a bad state.

Thanks for the backplane picture and glad you got the video working.
Can you take a good picture of the boot up screen showing the BIOS ID string ?
When you get the floppy working can you dump the bios using ROMSAVAT.EXE ? It is in the Getrom.zip here: http://cd.textfiles.com/microhaus/mhblackbox3/MEMORY/ and other places....

For the video artifacts, I've had problems like this a while back : Re: Let's improve video output quality of VGA ISA/VLB cards

Turns out my card had a faulty tantalum capacitor and a not very good ramdac.

Deunan wrote on 2022-02-11, 17:13:

As for missing floppy, is the ribbon connected properly? Don't assume the tab on the connector is in the correct place if it's a Sony drive. Also, are you using a CF card for HDD? Disconnect it, see if the floppy comes back.

I checked the cable direction on both ends and measured the supply voltages. I do have a Sony that I swapped in, and while it doesn't have a slot for the tab, it does have a (very) small arrow etched into the metal casing to indicate pin 1.

I reset the BIOS to failsafe settings ("Auto Configuration with Fail Safe Settings"), which didn't do anything. I tried disconnecting the IDE - no. Disabled the HDD in the BIOS - and that worked!

So then in an effort to confirm, I re-enabled the HDD. Still worked. Actually plugged in the CF adapter. Still worked. Played around with BIOS settings. Still worked. Swapped in the other floppy. Still worked. Added both floppies at once. Still worked.

Good news - everything works great.
Bad news- I have NO idea why the floppy stopped working. It seems the way to get this computer to work is to come here and ask for help.

As an aside, I did notice that the reset to failsafe doesn't seem to change many settings - nothing in the top two menus ("Standard CMOS Setup" and "Advanced CMOS Setup") that I could notice. I haven't messed with any of the timings in the third menu ("Advanced Chipset Setup").

Horun wrote on 2022-02-11, 22:56:

Can you take a good picture of the boot up screen showing the BIOS ID string ?
When you get the floppy working can you dump the bios using ROMSAVAT.EXE ? It is in the Getrom.zip here: http://cd.textfiles.com/microhaus/mhblackbox3/MEMORY/ and other places....

Sure thing. I'm attaching a photo where you can see the BIOS ID string. I'm also attaching a dump of the BIOS. Also, thanks for a link to that site... wow that's a lot of shareware. Brings back memories.

It looks like the ID string is

140-0331-001780-00111111-071595-ALI1217-H

Could you point me to the best resource for understanding those ID strings? I've never looked into what they mean. Clearly this BIOS is specific to this ALI chipset. This board has so many mystery jumpers that I'm hoping that there's a way to find out at least what they could be, if not what each one exactly is. I'm not above disassembling the BIOS if it comes to it.

Deksor wrote on 2022-02-11, 23:38:

For the video artifacts, I've had problems like this a while back : Re: Let's improve video output quality of VGA ISA/VLB cards

Turns out my card had a faulty tantalum capacitor and a not very good ramdac.

Ah! Thank you. I'll check this out. I don't recall the issue being there with the 8088 CPU, but I'll have to do some swapping to test. Text mode is great, so maybe i just didn't notice it. I'll have to go back and look at the pictures I took of my LCD after running some fractal drawing BASIC programs that use VGA mode. I can also see if passing the VGA through a VGA-HDMI converter changes the symptoms. My LCD has both VGA and HDMI inputs and responds differently to "out of spec" signals than the converter (see above about MDA video). Given my luck, the VGA card will spontaneously become perfect with no discernible reproducible cause.

Well, could've been a random bad connection somewhere. Or perhaps some glitch in the CMOS NVRAM that got fixed when you reset HDD settings.
BTW, the BIOS ROM you've uploaded seems to have incorrect checksum. Did you dump it with shadowing enabled in BIOS? If so turn it off, it's usually called System ROM shadow or F000 shadow, then re-dump. After that you can enable shadowing again.

Ok it is an Acrosser SBC from bios model AR-B1374. Unfortunately no B1374 found on their old archive site but did find manuals for B1375 and B1376 which might be helpful...
here is the 2005 list of manuals: http://web.archive.org/web/20050306033904/htt … load/manual.asp you have to filter website by URL to find the pdf's
Did notice that they had an FTP site back early 2000's but it was never archived....

added: comparing the 1375, 1376 and 1380 they all use the same M1, M2 and M3 jumpers and switch settings for same things so would assume 1374 does too.
here is links to 1375, 1376 and 1380:
http://web.archive.org/web/200603141438 ... (6)V15.pdf
http://web.archive.org/web/20060314141722/htt … ual/1380V10.pdf

NoTrueSpaceman wrote on 2022-02-12, 15:20:

Good news - everything works great.
Bad news- I have NO idea why the floppy stopped working. It seems the way to get this computer to work is to come here and ask for help.

Have you made any progress ? Can you redump the BIOS following Deunan's advice ?

Apologies for not responding sooner - I'm not receiving notifications of replies like I expect to.

Deunan wrote on 2022-02-12, 16:05:

BTW, the BIOS ROM you've uploaded seems to have incorrect checksum. Did you dump it with shadowing enabled in BIOS? If so turn it off, it's usually called System ROM shadow or F000 shadow, then re-dump. After that you can enable shadowing again.

I made sure to disable any shadowing in the BIOS and redumped the BIOS. `md5sum` shows that I got a different file, so hopefully it's correct this time.

Horun wrote on 2022-02-12, 18:53:

Ok it is an Acrosser SBC from bios model AR-B1374. Unfortunately no B1374 found on their old archive site but did find manuals for B1375 and B1376 which might be helpful...

added: comparing the 1375, 1376 and 1380 they all use the same M1, M2 and M3 jumpers and switch settings for same things so would assume 1374 does too.

Wow! Thank you for finding these! I'll dig into these and decode the jumpers on my board. When I do, I'll write up my findings for everyone to share. While it is only a 386sx and so has a 16mb limit on RAM, it'll suit my purposes wonderfully if the documentation works out.

I've summarized the available manuals and the board I have in hopes of finding some correspondence. There doesn't seem to be any. My board doesn't even have continuous labels - JP4 and JP5 seem to just not exist.

Just looking at the tables:
JP1 might be the clock selector (corresponds to JP3 on AR-B1380)
JP2 could be "PS/2 mouse selector" because it is near the PS/2 connector on the board. (ie: JP7 on the AR-B1380)
JP3 could have been for "battery charger selector" because it's near the battery, but it's unpopulated. (ie: JP8 on the AR-B1380)
JP4 and JP5 don't exist. They aren't unpopulated like JP3 - there just aren't any headers labeled with these identifiers.
JP6 is a total mystery. It's near the floppy connector, but also the main ALI chip. Candidates are "DE/E signal from M or LP" (has to do with driving a LCD panel so probably not), "1MX8 EPROM selector", or the "battery charger selector". Who knows?
JP7 is right next to one of the serial ports, so perhaps it's "RS-486 terminator selector" (ie: JP9 on AR-1380) or "RS-232/RS485 select" (ie: JP2 on AR-B3216).
JP8 could ALSO be "PS/2 mouse selector" because it's ALSO near the PS/2 connector on the board. (ie: JP7 on the AR-B1380)

The only one of these that sounds actually interesting is the clock selector - the chip is marked as 40MHz but the BIOS reports running at 33 MHz.

There are also the M1, M2, and M3 as well as the 8 positions of switches. I'm pretty sure these follow the AR-B1380, which has the same 9-pin headers and jumpers as well as a 8 position switch. On that board, these configure the various EPROMs, SRAM disks, Disk-On-Chips, IO ports, and whatever for the three sockets.

A hardware RAM disk sounds interesting, and I received the board with the chip required to create one, but I'm not looking to pursue it at this point.

1AR-B1380/1380A
2-------------
3FUNCTION                        NAME     PINS      JUMPERS
4RS-485 adapter selectors        JP1/JP4  3 (each)  1 (each)
5DE/E signal from M or LP        JP2      3         1
6CPU base clock selector         JP3      6         2
7LCD voltage selector            JP5      6         2
81MX8 EPROM selector             JP6      3         1
9PS/2 mouse selector             JP7      3         1
10battery charger selector        JP8      3         1
11RS-485 terminator selector      JP9      3         1
12S.S.D. &D.O.C. Selector         JP10     6         2
13RS-232/RS-485 selector for CN5  JP11     9         single 3x size
14
15
16AR-B3216
17--------
18FUNCTION                              NAME  PINS  JUMPERS
19CPU base clock select                 JP1   4     1 or 2
20RS-232/RS-485 select for COM B        JP2   3     1
21Battery charger select                JP3   3     1
221MX8 EPROM select                     JP4   3     1
23"VGA setting: IRQ 9 used occupied (*)
24Zero wait state (ZWS)"                JP5   4     0, 1, or 2
25DE/E signal from M or LP select (*)   JP6   3     1
26RS-485 terminator                     JP7   2     0 or 1
27
28
29AR-B1374
30--------
31FUNCTION   NAME    PINS          JUMPERS    CURRENTLY
32?          JP1     6             2          both across 2-3
33?          JP2     3             1          across 2-3
34?          JP3     space for 3   none       unpopulated!
35missing    JP4
36missing    JP5
37?          JP6     3             1          across 2-3
38?          JP7     3             1          across 2-3
39?          JP8     3             1          across 2-3