2Mourty wrote:

I finally got my Shuttle HOT-433 motherboard up and running! I'm really excited. I forgot how slow these old Socket 3 Systems are. 🙄 Anyways enough gushing; to my question; this mother board has settings for 40 Mhz and 50 Mhz bus speed. The processor I am running is an AMD 5x86. If I set the motherboard at 40 Mhz with a multiplier of 4 I get 160 Mhz. If I set the board at 50 Mhz bus with a multiplier of 3 I get 150 Mhz.

Which setting would have the best performance? The higher clock speed or the higher bus setting? Both settings are stable. The bios lets me manually set the pci and isa bus dividers so the bus speed is not a problem for the pci and isa cards.

Cool, the board with UM8881F chipset that support EDO ram 😁

With 3x50mhz you'll obviously get the best overall experience.

Any chance you can run the pcplayer videospeed benchmark util and post your results here?

I have to disagree about about the 3x50 setting being optimal. While in theory it should be faster, as it turns out your cache chips are only 15ns (it's possible to get 12ns parts though). Running 50MHz with 15ns SRAM you're going to have to add a bunch of wait states. This in turn decreases memory bandwidth. you will also take a hit on PCI performance. A PCI card might be able to cope with 40MHz, but 50MHz is way out of spec. Thus, you'd have to use a PCI divider and your PCI will putz along at 25MHz. Running at 160MHz will also give you superior integer performance.

However, running the undocumented 60 or 66MHz FSB might be interesting. It might be enough to counter the effect of added waitstates (assuming you don't have to disable the L2 cache altogether). Your 5x86 might be hard pressed for 180MHz, but if you can get your hands on one of the enhanced am486s that is fabricated on the .35 micron process and supports 2x multiplier you should be in business. A Cyrix 5x86 with 2x multiplier should also be able to pull it off. I have the parts to do this but I haven't gotten around to testing yet, and therefore I don't know what kind of benefits or disadvantages there are to this setup.

Anonymous Coward wrote:

I have to disagree about about the 3x50 setting being optimal. While in theory it should be faster, as it turns out your cache chips are only 15ns (it's possible to get 12ns parts though). Running 50MHz with 15ns SRAM you're going to have to add a bunch of wait states. This in turn decreases memory bandwidth. you will also take a hit on PCI performance. A PCI card might be able to cope with 40MHz, but 50MHz is way out of spec. Thus, you'd have to use a PCI divider and your PCI will putz along at 25MHz. Running at 160MHz will also give you superior integer performance.

However, running the undocumented 60 or 66MHz FSB might be interesting. It might be enough to counter the effect of added waitstates (assuming you don't have to disable the L2 cache altogether). Your 5x86 might be hard pressed for 180MHz, but if you can get your hands on one of the enhanced am486s that is fabricated on the .35 micron process and supports 2x multiplier you should be in business. A Cyrix 5x86 with 2x multiplier should also be able to pull it off. I have the parts to do this but I haven't gotten around to testing yet, and therefore I don't know what kind of benefits or disadvantages there are to this setup.

You're right, forgot that the 5x86 is a true "DX4" 4x40mhz is much better

At 150mhz (50mhz bus speed, x3) things froze more often and things got unstable. I couldn't boot at 200mhz either (of course). The performance gain from a 50mhz bus speed was very marginal and not useful for zdoom or Quake.

I'd just stick to 160mhz (40 x4, best performance and stability is here imo) or 120mhz (40 x3)
You might want to play with memory timings too, mine's aggressive but prevents the computer from soft resetting. 🙁

leileilol wrote:

At 150mhz (50mhz bus speed, x3) things froze more often and things got unstable. I couldn't boot at 200mhz either (of course). The performance gain from a 50mhz bus speed was very marginal and not useful for zdoom or Quake.

I'd just stick to 160mhz (40 x4, best performance and stability is here imo) or 120mhz (40 x3)
You might want to play with memory timings too, mine's aggressive but prevents the computer from soft resetting. 🙁

Think he has a better chance with these settings since he has a better motherboard

Perhaps, but even with a decent motherboard there really isn't any feasible speed benefit from a slower multipler and faster bus versus the versa.

I would be happy to run the test for you 40/160. Would you show me where I can download the program? Also I will try it at 50/150 later this week.

I did not know about the 60/66 mhz speeds, as you said they are undocumented. Can anybody point me to where I can find this information?

Also it would be fun to try this with one of the am486 chips. I could have some fun with that. How can I make sure if I try to by this on ebay that it is one of the enhanced chips?

I also managed to find a copy of quake at the local thrift store. I've never heard the NIN music before so this is kind of fun. What sort of performance can I expect on a 486 at 160 mhz. I know the game was designed around the pentium fpu so my guess is that it would be sluggish at best. Thank you for the help!

At 160MHz, (40x4) you should expect 12fps-ish, with much slowdown in areas with dynamic lights but not as bad as other settings. This isn't far from the performance of a Cyrix6x86MX200 (which is very bad at Quake, 14fps) but still a far cry from the Pentium 100MHz (21fps)

At 150MHz (50x3) the FPS is roughly around 9.

At 120MHz, (40x3) it's 7fps and is very, VERY sluggish. Performance very much like the Intel 486DX4-100

2Mourty wrote:

Would you show me where I can download the program?

PCPBENCH.ZIP

You would probably have to look up the model printed on the chip to know what it is. Not all of the enhanced chips are the same. I believe that the am486DX2-66 fabricated at 0.35u is 16BGC. I know there is also a 0.35u 16kb DX4, but I don't know the model number off hand. However, with the DX4 I am not sure you would be guaranteed a 2X multiplier since I heard they are really remarked 5x86 chips.

It might be easier to get your hands on a Cyrix chip. Most of the 100Mhz models are overclockable and are guaranteed to have a 2X multiplier.

cpu-world.com has this nifty identification table. (scroll down a bit for the enhanced 486 models).

I will be out of town until Saturday night. I will do the test then. Thank you for posting the pcbench. I had fun running in dosbox yesterday to see what the score would be.

If anybody knows the settings for the 60/66 mhz bus speed that would be helpful also. This forum is great, thank you for the help.

I'm having problems with my serial headers! For the life of me I can't get a serial mouse to work which is severly hampering the usability of my 486. It is a bit frustrating. I was able to install Windows 95 osr 2.5 and I ran the benchmark without installing the video card drivers or s3vbe and got a measley score of 8.1. That score was at 40/160 with an s3 virge card. That seems a bit low to me. I may have to buy and isa serial card....

2Mourty wrote:

I'm having problems with my serial headers! For the life of me I can't get a serial mouse to work which is severly hampering the usability of my 486. It is a bit frustrating. I was able to install Windows 95 osr 2.5 and I ran the benchmark without installing the video card drivers or s3vbe and got a measley score of 8.1. That score was at 40/160 with an s3 virge card. That seems a bit low to me. I may have to buy and isa serial card....

What kind of nature is the problem?

You probably have the wrong plugs.

I found the undocumented 60 and 66 mhz bus settings for my motherboard here:

http://translate.google.com/translate?hl=en&s … ficial%26sa%3DG

Now if I can get a plug that works with my headers and a cpu that has a real 2x multiplier I could have some really interesting fun.

I know the pentium overdrive for socket 3 really is a worthless chip, but I wonder how it would perform with a 66 mhz bus....

Keep dreaming. You'll be lucky to get it to work with 40MHz bus.

I always was fascinated by the true 486DX/50. 50 MHz bus, 50 MHz CPU. Rare it was.

40 is usually ok, but that's the limit pretty much. On a VLB mobo, you often need wait states added to do even 40 MHz. I've never had a VLB or PCI mobo doing 50 MHz. If you could pull it off, you'd almost certainly need dividers on the buses and end up with a not-so-hot 25 MHz VLB / PCI.