Yeah, i know the feeling as i had few motherboards acting like that. Why? I don't know.
Btw, change the keyboard controller and see if that makes a difference.

Hi there! I also have this board ..

pshipkov wrote on 2023-02-25, 22:47:

First in line is Matra 486SLC2 VESA based on EFAR Microsystems 82EC392, 82EC495 (relabeled OPTi 82C392, 82C495B) chipset, hidden under cool stickers with the word "PATH" written on them.
...
The AWARD 4.51 BIOS resembles 486 layout and type of options. There are quite a few timing settings.

Do you happen to have this BIOS dumped? TRW only has the 4.50 BIOS (same as I have on my board).

pshipkov wrote on 2023-02-25, 22:47:

Similar to Alaris Leopard this motherboard was not happy with most VLB EIDE controllers - their DOS drivers hang during initialization.
DTC 2278E worked fine but had to be slowed down a lot which kind of defeated the point of using an EIDE controller. If nothing else it proved that 2278E is one of the most compatible guys around.

I also have a few Leopards, and my usual Promise DC4030VL-2, EIDE4030PLUS, DC200 (ISA) and Tekram/Buslogic DC690C/CD controllers work just fine on those. On this board, however, nothing with a boot BIOS seems to work properly:
- The DC4030VL-2 and DC200 triggers the BIOS, but if external cache is enabled, it hangs when attempting to boot from HDD. It's a full-on wedge; reset required. With external cache disabled, they work fine.
- The Tekram DC690C will not trigger the BIOS at all.
- The EIDE4030PLUS causes "HDD controller failure" after a long pause during POST.

No amount of modifying timings or shadow/cache settings (in system BIOS or controller BIOS) makes a difference. I have also triple-checked the onboard cache; it does seem to be configured correctly.

Do you have any idea what might be wrong here? I'm hoping a newer BIOS might help. There should also be an MRBIOS out there for this card, but I haven't seen it..

Nevermind most of the below: Seems like my upper 128KB cache was bad; reducing to 128KB allowed the system to boot with the DC200 and the 4030VL-2.

My sysbench scores are about the same as yours. I'd like to find RAM that is fast enough that I can use "quick write" as well, not just "quick read".

Also curious how much past 80MHz I can push the CPU, but that's for another day .. first I have to find out why the cache is bad.

At least now I can run a 3-card VLB system - VGA, IDE *and* Ethernet :D

/Eirik

ltning wrote on 2026-02-16, 22:41:

Hi there! I also have this board .. […]
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Hi there! I also have this board ..

pshipkov wrote on 2023-02-25, 22:47:

First in line is Matra 486SLC2 VESA based on EFAR Microsystems 82EC392, 82EC495 (relabeled OPTi 82C392, 82C495B) chipset, hidden under cool stickers with the word "PATH" written on them.
...
The AWARD 4.51 BIOS resembles 486 layout and type of options. There are quite a few timing settings.

Do you happen to have this BIOS dumped? TRW only has the 4.50 BIOS (same as I have on my board).

pshipkov wrote on 2023-02-25, 22:47:

Similar to Alaris Leopard this motherboard was not happy with most VLB EIDE controllers - their DOS drivers hang during initialization.
DTC 2278E worked fine but had to be slowed down a lot which kind of defeated the point of using an EIDE controller. If nothing else it proved that 2278E is one of the most compatible guys around.

I also have a few Leopards, and my usual Promise DC4030VL-2, EIDE4030PLUS, DC200 (ISA) and Tekram/Buslogic DC690C/CD controllers work just fine on those. On this board, however, nothing with a boot BIOS seems to work properly:
- The DC4030VL-2 and DC200 triggers the BIOS, but if external cache is enabled, it hangs when attempting to boot from HDD. It's a full-on wedge; reset required. With external cache disabled, they work fine.
- The Tekram DC690C will not trigger the BIOS at all.
- The EIDE4030PLUS causes "HDD controller failure" after a long pause during POST.

No amount of modifying timings or shadow/cache settings (in system BIOS or controller BIOS) makes a difference. I have also triple-checked the onboard cache; it does seem to be configured correctly.

Do you have any idea what might be wrong here? I'm hoping a newer BIOS might help. There should also be an MRBIOS out there for this card, but I haven't seen it..

My notes are about overclocked systems. Will reword the previous posts to clarify that. But i doubt this is actually a big factor.
Will retest with Alaris Leopard soon as i dont have the Matra board anymore.
What video card you are testing with?
Did you test the VLB EIDE/SCSI adapters with their DOS drivers loaded? That's were i had problems.

Will link your posts here from my older posts as you bring a change to the story. Thanks.

Yes, 4.51 BIOS version, but recent NAS issue corrupted some files. Including this one.
EDIT: May ask the new owner of the board to provide the microcode.

Here is that Matra SLC bios. I have not really gotten around to playing with the board yet. All my free time has been tied up in 286 overclocking or RealDOOM development.

I have run a similar board (IBM 486SLC2) at 80 mhz before. Some benches were recorded here:

https://www.youtube.com/watch?v=9kKBbYy0zoM

I see you managed 2x50 mhz as well, very cool. I recall i had to do multiple boots with different jumper positions to trigger a boot at these speeds. I wonder if a 50 mhz clock was possible somehow, but I also don't just have spare IBM SLC/BL chips lying around to bin like I do with other processors.

I also have some recordings of 286 at 37.5 mhz on the SCAMP chipset there. I have posted as high as 41 mhz, really the RAM and then CPU become the limiting issue.

Some notes on video cards...

Recently I discovered the ET4000W32/I to be my best performer, but they are a little hard to find. Aside from that, the 5426/5429 based Diamond Speedstar Pros are pretty common and should outperform ET4000AX, but it's close. They do regularly tolerate bus speeds of 33-37 mhz while most ET4000AX fail around 24-25 mhz. Mostly i think this results in better synthetic scores (chr/ms and such) but it doesn't translate to a lot of fps gain in game etc benchmarks.

I may modify a 5434 bios soon for 286 compatibility. I disassembled the diamond one a while back ( https://github.com/sqpat/5434bios/blob/main/5434bios.asm ) and determined it shouldn't be too much work. Ironically the 32 bit code is mostly looking for the pci bus for conflicting vga cards on the bus, to disable the isa card if a pci vga card is found. It's a bit obfuscated and I haven't gotten around to it but I had interest it seeing if it would outperform the other top ISA cards in dos performance.

First of all - thank you for the quick turnaround providing the bios.

Let me unpack your post as it is contains quite a bit of interesting information.

Real Doom - very cool. Been watching on and off that project.
Did you consider unreal mode access to extended memory?
This may be perf net-negative for 286 cpus - tbd. And a deal breaker for 808#. But still.

Share more info for the SCAMP 286 overclock. Is it long term stable? Which motherboard? This chipset is very slow, maybe thats why it offers such overclocking room.
What CPU was used? So far all Intersils and Harrisses here start to flake at ~35mhz on air cooling.

I assume you are talking about ISA video cards, correct?
My findings are similar. ET cards are good if playing safe, otherwise CL gets you much further.

Getting CL GD-5434 to be 286 compatible will be very welcome. Let us know if you make it happen.

Hmm. I don't think unreal mode will be great for RealDOOM, segment changes are frequent and my understanding is they are quite slow when descriptor caches are involved. It would also not be a very easy rewrite from the current code due to a lot of assumptions in the code about things being in real mode, segments 16 bytes apart, etc. More likely is an EMS 3.2 version that would be more compatible with chipsets such as HT-12, NEAT, etc. This will probably also come with a 10 or 15 percent speed loss too though, as I can't maintain large texture caches.

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The SCAMP overclock came off a Biostar MB-1220VS. One neat thing is it has a separate crystal for bus and cpu clock so you can actually run them at completely independent speeds, including a faster bus clock than cpu clock. I have run bus as high as 43 mhz I believe (with slower cpu clocks). As for stability, at 37.5 mhz maybe it could be stable eventually. I do not think the chipset or cpu in my case are the problem, the problem is really the ram at 0 ws. I don't have ram that can keep up with those speeds. I think I actually put the ram and video card in the freezer for 5 minutes to get the 37.5 mhz case to work (a nice quick and easy alternative to peltier etc for light testing, put it in a bag in the freezer to precool to near freezing temps). I since have gotten more stable video cards but RAM is still an issue. Anything over 33 mhz or so is always a problem for long run times. If I had RAM tolerant of higher speeds, then I think 37 might be stable for the machine. I might have to try some things like windows, etc to see if the graphics card is stable outside of dos in some other applications. I even have some simms with FPM drams marked 45/50 ns but they do not keep up with some of these ibm branded 60 ns chips. I'd really like to investigate modern faster ram designs at some point in the future. In the worst case, maybe a dram module benchmarker, such that individual simms could be put together with high performing dram modules only.

If I had faster ram with a lot of overhead, I would love to try to get some bench high scores and pushing a chip with peltier/etc past 45 mhz, maybe even 50 on the board. But if i wanted to stop somewhere stable, I think 35-38 range would be where I would stop. The graphics card starts to glitch in some video modes a few mhz above that, and I would want to give the cpu a little bit of breathing room too.

As far as stable performance, this reminds me - One thing I have experimented with is sanding the tops of 286 cpus. You can sand several mm off the top of the 286 and reveal the copper(?) ground plane inside the cpu eventually. (My understanding is the core is on the underside of the PLCC packaging). If you get to the copper core, my experience in air cooling is that now you can maintain higher stable temperatures than before. For example a cpu that posts at 34 but crashes after 3-5 minutes of running will run at least 15-20 minutes, maybe indefinitely in this state. I attached an example photo.

On the subject of fast 286, I've been thru a few hundred chips and binned quite a lot. I think in general the "cs80c286-25" available from china is in the best case rebadged cs80c286-20 (and sometimes outright different plcc68 chips), so I've stopped buying the 25s and started buying more 20s because at least they are less likely to be modified with faked batch codes and dates and I can collect better information on chips. Of these 20 mhz chips, yeah I think in general 34-35 mhz starts to become difficult to beat. I think if you can find date codes before 1994 or so, the silicon seems to be better, or maybe it was less aggressively binned to other SKUs back then. All my really good chips seem to be in those dates. I have some guesses but no evidence - I think maybe they started to bin better chips and selling them as IS80C286-20/25 after some date. I can't find any legitimate stock of these outside of the ones that are priced very expensive.

I have purchased many of the new stock chips (intersil, harris..) as well. They are usually disappointing, most are in the 27-31 mhz range. I can't say for sure that they will all be this way, but when you buy the new chips you will keep getting the same batch codes, so it's not a surprise the performance will be very similar across them. I have tried to ask suppliers for older stock but they more or less just ignore you. Maybe there do exist good newer chips too, but I haven't seen them and its hard to get variety.

In the past 1-2 years there was a seller on ebay with some legitimate cs80c286-25 stock in the US, and there have been a few with cs80c286r1787 stock. Some of those cs80c286r1787 will do really well. If you have one soldered to a random ht-12 board or something it might be worth desoldering and checking out on another board. I think they are all early 90's chips from the same general stock that made cs80c286-20/25.

---

I also attached a photo of a fan mount i 3d printed for a 286 in this state. To be honest the airflow is not great. Probably better off with a case fan sucking airflow thru the front of the case is much better, but it's cute. The mount essentially must be glued to the top of the cpu and the fan is offset a bit such that the air should hit the fins of the heat sink. If you have any interest I can post those stl files.

M2 heatsinks are conveniently perfectly sized for cooling 30 pin SIMMs. It will require some sort of thermal glue or tape to stick to the dram modules. I have not been able to determine this helps with stability. I think the dram packages overheat before they can be cooled thru their packaging.

Rodney over at the vcfed forum has been working on 286 board designs for a couple years. https://forum.vcfed.org/index.php?threads/pro … m-5170.1243108/

His most recent work is on a FPGA based chipset, which is not complete yet. But prior to this was a CPLD based chipset. He built it with SRAM, but it turns out SRAM is not as easy to get 0 ws because of the way 286 pipelines high address bits which is more conducive to dram and chip select. He got that board stable at 20 mhz though, and designed an EMS 4.0 compatible memory controller and I wrote an EMS driver for him and he ran RealDOOM on the board which was very cool. I've sent him some hardware and faster chips for him to be able to tes this designs with. Who knows, maybe the FPGA design will reach 25-30 mhz with 0 ws as he experiments with different things. He has also experimented with TOPCAT and SCAMP based designs.