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Poll: Does DOOM lag because of my graphics card or my CPU?

Poll: Does DOOM lag because of my graphics card or my CPU?

  • Graphics card

    Votes: 2 25.0%

  • CPU

    Votes: 6 75.0%
  • Total voters
    8
T

themikepeng

Experienced Member
Joined
May 17, 2012
Messages
71
Location
San Diego, CA
I got this 486DLC for DOS gaming, and Wolfenstein, Police Quest, and other older games ran perfectly fine. However, when I tried DOOM and some other newer games, they lagged and were just less than playable. I would really like to know if this is because my CPU or video card (or both?) The 486DLC is an upgrade from the 386, so it is not exactly up to speed. There is no coprosessor either. The video card is ISA, not VLB or PCI. The power supply is dated 1992. It cannot possibly be the memory because I have 30mb of 30 pin simms. Either way I will have to upgrade my motherboard. If the lag is because of the CPU, I can just get any 486dx(2)(4) motherboard and slap in the old ISA graphics card. I don't plan on getting a VLB card because they are huge and cost more than the motherboards themselves. If I get a 486 board with a PCI slot, it will upgrade both the CPU and the graphics card, however this is a lot more expensive and not as nostalgic. I only need to know, does DOOM lag because of my cruddy CPU, or my even worse graphics card?
 
It's not lack of memory, but the disparity between the memory speed and the speed of the processor can play a big part in performance, especially in this particular era. Does this motherboard have any cache, or is it just the internal 8KB?

Graphics card can certainly also be a factor, but not as much as cache.
 
If you have a 486DLC, which has 1K of internal cache, I would suggest that your ISA video card is more likely causing a performance bottleneck. What speed is your processor running at? What chipset is your ISA card using? For a graphics intensive game like DOOM, the graphics card is just as much an issue as cache. It does not use a coprocessor.

Slapping an ISA graphics card in a 486 is not going to do DOOM many favors. You have two choices, either get a VLB card or a PCI 486 board. I found a decent deal on the former not too long ago.
 
The CPU is the bottleneck. ISA VGA is fast enough to keep up at 320x200.
 
Great Hierophant is correct, get a VLB video card. I play DOOM on several of my 486's with no problems. My favorite is the Diamond Speedstar Pro w/1 MB on-board. I also like the Matrox Millenium w/2 MB daughter board in my 486 PCI.
 
You may want to check and make sure the cache is enabled, and that the turbo function isn't set to run in slow mode. A 486DLC should be able to handle Doom just fine, even with a crappy ISA card like a Trident or whatnot. I mean, you'll run into slowdowns here and there, mainly in the larger levels, but it should be playable.
 
In my experience switching from an ATI VGA Wonder (ISA) to a VLB card made a big difference in the playability of DOOM on my 486DX2/66.
 
Well, I have basically the same video card in my 386DX/40, an ATi 'Graphics Ultra' or whatever it was they called it... in DOS it functions as a regular 'VGA Wonder'. Doom runs alright on that system, even at full-screen in high-detail mode.
 
Sorta interesting, I was searching for the specs, I did come across this readme.txt that should be from one of the first versions. I'll go ahead and just rip the text here
Code: 
-------------------------------------------------------------
SYSTEM REQUIREMENTS
-------------------------------------------------------------
DOOM(TM) requires an IBM compatible 386 or better with 4 megs of 
RAM, a VGA graphics card, and a hard disk drive. A 486 or 
better, a Sound Blaster Pro(TM) or 100% compatible sound card 
is recommended. A network that uses the IPX protocol is 
required for network gameplay.

While it might be slow (you can toggle the full screen setting, I do remember some games needed a faster processor to play full screen vs windowed mode) it should be playable one would think. I don't think 3d accelerators were popular at the time or perhaps I didn't realize what they were but you did eventually start realizing the memory/cache on a video card could help play real 3d games. Other than that I thought it was mostly cpu/math coprocessor performance that mattered in the early 3d games.

Looking more at it and your later post, do you not have a math coprocessor in the system? (I guess it takes the 387?). That would likely be the catch that will make or break performance. I'm also not sure since I'm seeing the 486dlc referenced like it's only a 386 so you'd be on the low end of the requirements. Without a coprocessor a 386 would certainly lag trying to keep up.
 
I not so sure that the freeware version of DOOM supports a FPU. I don't have a 386 built up at the present to test that point, but I'd be willing to bet a nickle to a hole in a doughnut that it wouldn't make much difference. I"m wondering if anyone out there who has an FPU in their 386 would be willing to check that out.
 
Last edited:
Doom was 100% fixed point. An FPU will not help.
Click to expand...

In fact, there were only a handful of old DOS games that did support an NPU. SimCity, I think some of the flight simulators, and... that's about all, really. I believe Quake was the first shooter game that used one, and of course that ain't gonna run on a 386-class machine regardless.
 
I seem to remember the sound card could cause DOOM II to slow down, but can't remember the details. Maybe try running it without sound just to see if that makes a difference.
 
I would try reducing the installed RAM to 16MB or less in case your motherboard enforces slower memory access when having excessive amounts of installed RAM. 8MB should be more than enough for DOOM.

CPU should run DOOM fine. Video card should run DOOM fine. That leaves some form of system problem: incorrect jumpers, mismatched memory, some background process or device driver.
 
Looks like it is the CPU or something else. So a if 486sx has more cache, will it be any improvement? Or will I have to get a 486dx with an fpu?
 
A larger cache might help but it might not help enough. A clock doubled or tripled model might be even better. However, I expect that you may need a new motherboard to get any sort of increase. You have a motherboard that shipped with a 386 which you upgraded to 486DLC which means it probably has a 132 pin socket. The better 486 models are mostly available for 168 pin sockets and won't fit in your current motherboard.
 
FWIW, I just upgraded the L2 cache of my 486dx2/66 from 128kb to 256kb. This gave me a good 20% improvement in frame rates, going from around 20fps to 25fps. Specifically, that's 3660 realtics with 128, and 2990 realtics with 256, with 'doom -timedemo demo3'.
 
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