VOGONS


First post, by Xaleros

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Hello, I'm not sure if this is the correct forum category but from what I've seen I think this fits here. I'll try to keep this as organized as possible

I recently found a boxed copy of The Ultimate Doom at a Goodwill and decided that now was as good of a time as any to get some kind of DOS gaming machine going. Luckily for me, a friend of mine had a 486DX4-100 build that he had gotten awhile back. He didn't use it a whole lot so he offered to give it to me instead. After a dead 3.5" floppy drive and some driver hunting, I finally managed to get DOS installed and the CD-ROM drive working. Installing Doom worked fine and once I started the game, I was greeted with an awful framerate (I wanna say about 10-15 FPS, from what I've seen on youtube it almost looks like a 386 is running it). If I shrink the screen size to about half it runs fine.

I began troubleshooting a number of things, none of which had any effect. Eventually I did more digging into what motherboard I have and found this forum post -> 486 VLB UMC-Chipset, what is it?

I've read through this forum post top to bottom several times and triple checked the jumper settings on the motherboard. Some things I tried were:
- Running without sound or music
- Running without the CDROM driver
- Running without HIMEM or EMM386
- Running with only one of the two 16MB EDO sticks that I have.
- Running without any external cache enabled
- Running with failsafe BIOS settings
- Changing the jumpers for the CPU clock speed (Combination of JP5 and JP6 seem to have very strange behavior)
- Changing the jumpers for the CPU type (BIOS says "i486DX4" despite the cpu being configured for Am486DX4-100, I don't think that is correct)
- Setting cache read/write waitstates to minimum
- Running with only necessary ISA perphierals (Floppy/HDD controller, vga card, etc)

The only lead I have is that when I probe the CLKMUL pin, it does not seem to be high as it should be if it is in use, based on the manual for this CPU. I've been at this problem for about three or so days and I'm pretty much at wits end. Is there something really simple that I haven't done yet that is preventing the CPU from running at full speed or is the motherboard damaged and/or missing components? Below is a list of specs and pictures of the output after POST, the jumpers for CPU speed, and the jumpers for CPU type. Try not to mind my horrible phone camera, I labelled which jumpers are which to avoid confusion. Let me know if I need to post any extra information.

Specs:
CPU: Am486DX4-100NV8T
Motherboard: F4DXL-UC4D
RAM: 2x16MB EDO 60ns
HDD: Seagate Medalist 4321 4.3GB
ISA Peripherals:
PT-604A HDD/Floppy Controller
Mitsumi 74-1645A CDROM Controller + Drive
Sound Blaster 2.0 CT1350
Linksys Ether16 LAN Card
Trident TVGA900A

CPU Type Jumpers:
WEsecfW.png

CPU Speed Jumpers:
jwiRUdL.png

POST Output:
5mgey4n.png

Reply 2 of 13, by Xaleros

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I think you're definitely right. I don't know why but I assumed (bad idea, I know) that older games would run fine for some reason, but never bothered to try. Even Keen1 and Wolf3d don't run as well as they should. Wolf3d shows very similar symptoms to Doom (doesn't run as bad as Doom but it's still pretty bad considering its a 486). I'm going to look around and see what kind of GPU I should be getting but if you (or anyone else) has a suggestion, let me know cause I guess I'm pretty green with older hardware. I guess VESA 2.0 cards aren't a bad bet?

Reply 3 of 13, by fitzpatr

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It may be more complicated than just the Trident.

Another of our forum members, gerwin, had similar issues with an AM486dx4-100 on this exact board, and found a solution.

Please read through this thread. The solution is around two-thirds down the first page, and involves changing wait states in the BIOS.

MT-32 Old, CM-32L, CM-500, SC-55mkII, SC-88Pro, SC-D70, FB-01, MU2000EX
K6-III+/450/GA-5AX/G400 Max/Voodoo2 SLI/CT1750/MPU-401AT/Audigy 2ZS
486 Build

Reply 5 of 13, by Xaleros

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fitzpatr wrote:

It may be more complicated than just the Trident.

Another of our forum members, gerwin, had similar issues with an AM486dx4-100 on this exact board, and found a solution.

Please read through this thread. The solution is around two-thirds down the first page, and involves changing wait states in the BIOS.

Yup I tried that. I mentioned in my original post but sadly it had no effect 🙁

I did see some jumpers on the Trident but couldn't find any information for the specific model I have. Tried every possible combination that I could and nothing seemed to change as far as performance goes. I'll play around with the BIOS settings a bit more but I doubt I'm gonna get much results

Reply 6 of 13, by fitzpatr

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Xaleros wrote:
fitzpatr wrote:

It may be more complicated than just the Trident.

Another of our forum members, gerwin, had similar issues with an AM486dx4-100 on this exact board, and found a solution.

Please read through this thread. The solution is around two-thirds down the first page, and involves changing wait states in the BIOS.

Yup I tried that. I mentioned in my original post but sadly it had no effect 🙁

I did see some jumpers on the Trident but couldn't find any information for the specific model I have. Tried every possible combination that I could and nothing seemed to change as far as performance goes. I'll play around with the BIOS settings a bit more but I doubt I'm gonna get much results

So you have!

Two possibilities come to mind.

The first is the aforementioned video card. The Trident 9000A is quite a weak performer, and any ISA card will show down a dx4 100, let alone that one.

The next is the turbo button. I didn't see any mention of it in your post, so I don't know if you've tried the switch, or, in lieu of a switch, a jumper. Try it in both positions of you haven't already.

MT-32 Old, CM-32L, CM-500, SC-55mkII, SC-88Pro, SC-D70, FB-01, MU2000EX
K6-III+/450/GA-5AX/G400 Max/Voodoo2 SLI/CT1750/MPU-401AT/Audigy 2ZS
486 Build

Reply 7 of 13, by wouterwashere

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Have you tested the CPU speed with a bench tool like Topbench?

If it doesn't rate correctly for the type of CPU you have, you know that that has to be fixed first with BIOS / jumper settings.

Reply 8 of 13, by Xaleros

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fitzpatr wrote:

The next is the turbo button. I didn't see any mention of it in your post, so I don't know if you've tried the switch, or, in lieu of a switch, a jumper. Try it in both positions of you haven't already.

My apologies, I thought I mentioned that. The turbo button is active and I have tried switching it on and off to see if there's any positive effect. Everything runs generally slower when the Turbo LED is off.

wouterwashere wrote:

Have you tested the CPU speed with a bench tool like Topbench?

If it doesn't rate correctly for the type of CPU you have, you know that that has to be fixed first with BIOS / jumper settings.

I actually did not think to look for a benchmarking program (honestly what was I thinking 🤣), I tried it out and this was the results I got.

nlNJw0A.png

Although it does not match, it looks like the CPU is performing as it should. I did a bit of digging around and decided that I'd invest in a CL5248 card. Wasn't the absolute best from what I saw but it's within my price window for the time being and it seemed like that had a generally good reputation. I'd much prefer to get a PCI card but this thing (as expected) lacks the proper slot on the motherboard.

Reply 9 of 13, by wouterwashere

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A score of 127 is a bit low, if I interpret the database well. Most 486DX2-66 rate between 170 and 190, say 180 on average. If the score is linear, this would imply that yours is running at about 50MHz (66 MHz / 180 * 127 = 45,6 MHz). But again, I don't know if you can do this.

I will give it a run on my 486DX-33 and see what score I get.

Reply 10 of 13, by Disruptor

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Try to run ctcm from c't magazine (heise).
ctcm
ctcm /nop (if command before fails)
ctcm /vid
Also try Speedsys 4.78

A general rule in the age of the 486 was to avoid graphic cards from Oak, Realtek and Trident. Tseng (ET4000W32, ET4000), S3 and Cirrus Logic have been better.

Reply 11 of 13, by fitzpatr

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Xaleros wrote:
My apologies, I thought I mentioned that. The turbo button is active and I have tried switching it on and off to see if there's […]
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fitzpatr wrote:

The next is the turbo button. I didn't see any mention of it in your post, so I don't know if you've tried the switch, or, in lieu of a switch, a jumper. Try it in both positions of you haven't already.

My apologies, I thought I mentioned that. The turbo button is active and I have tried switching it on and off to see if there's any positive effect. Everything runs generally slower when the Turbo LED is off.

wouterwashere wrote:

Have you tested the CPU speed with a bench tool like Topbench?

If it doesn't rate correctly for the type of CPU you have, you know that that has to be fixed first with BIOS / jumper settings.

I actually did not think to look for a benchmarking program (honestly what was I thinking 🤣), I tried it out and this was the results I got.

nlNJw0A.png

Although it does not match, it looks like the CPU is performing as it should. I did a bit of digging around and decided that I'd invest in a CL5248 card. Wasn't the absolute best from what I saw but it's within my price window for the time being and it seemed like that had a generally good reputation. I'd much prefer to get a PCI card but this thing (as expected) lacks the proper slot on the motherboard.

I expect that you will approximately double your performance in most things with a 5428, assuming that it's a VLB-based card.

MT-32 Old, CM-32L, CM-500, SC-55mkII, SC-88Pro, SC-D70, FB-01, MU2000EX
K6-III+/450/GA-5AX/G400 Max/Voodoo2 SLI/CT1750/MPU-401AT/Audigy 2ZS
486 Build

Reply 12 of 13, by Xaleros

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fitzpatr wrote:

I expect that you will approximately double your performance in most things with a 5428, assuming that it's a VLB-based card.

Yeah you were pretty much spot on. Got my CL5248 today and immediately plopped it in. My phone is dead so I can't show off a "screenshot" but topbench reported a score of about 226. Fired up Doom shortly after and it runs flawlessly now! I guess I overestimated how much power it took back in the day to run things at a mere 320x240 but hey, it works now.

Reply 13 of 13, by fitzpatr

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Excellent! I'm glad you're getting better performance now. Graphics cards were not as critical then as they are now, but if they're weak, the system will drop like a stone. The Trident cards, especially the early 8900 and 9000 cards, were notorious for being weak. Couple that with the ISA bus limitations and a fast 486, and it can kill the performance in anything remotely graphics intensive.

MT-32 Old, CM-32L, CM-500, SC-55mkII, SC-88Pro, SC-D70, FB-01, MU2000EX
K6-III+/450/GA-5AX/G400 Max/Voodoo2 SLI/CT1750/MPU-401AT/Audigy 2ZS
486 Build