Re: Interposer between Cyrix 486 and motherboard

Posted on 2024-04-23, 08:41

by

by MSxyz

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

For me it seems this CPU / FPU combination is like a Cyrix 386 (486DLC) + 387 (3D87) adapted for the 486 bus, with some cache but lack of burst mode. Since the FPU is not integrated in the CPU it won't take advantage of the L1 cache. This is also my impression. I plugged in an Am486DX2 80MHz in the …

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Re: Interposer between Cyrix 486 and motherboard

Posted on 2024-04-23, 06:45

by

by MSxyz

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Finally I managed to dedicate myself to this Cyrix 486 + 487 sandwich :) My new board is a later revision of the same Soyo 025 they originally came with. The board is actually quite different (different chipset, a SiS 85C471, different layout different number of VESA slots...), so I don't know why …

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Aquarius Systems MB-5DVP

Posted on 2024-04-17, 16:09

by

by MSxyz

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I purchased this peculiar motherboard: https://theretroweb.com/motherboards/s/aquarius-systems-mb-5dvp One of the few VLB+PCI motherboards. It's for socket 4 CPUs (5V P5) I can't find online any manual scan or a list of the jumper settings. Does anyone has some info? I understand it's pretty rare …

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Re: Asus VL/I-486SV2GX4 with 60MHz bus?

Posted on 2024-04-10, 15:59

by

by MSxyz

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

You re right. I mixed up the high value with pseudo ECL. That's what happens when I use my memory instead of doublechecking what I seem to remember. Also, apologies if it seemed I was lecturing... I was only commenting that "Physics will do as it's told" seems a bit strong statement. Usually its …

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Re: How common are graphic cards for the ECS Local Bus?

Posted on 2024-04-10, 09:22

by

by MSxyz

in Marvin \ Video

in Marvin \ Video

Oh, you may want to check this post , I don't think it was linked above. Thanks. I did read that post before. According to the posted benchmarks, my motherboard is performing more or less the same; I'm getting slightly better scores with real life applications (Doom, Quake) and slightly worse in …

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Re: Asus VL/I-486SV2GX4 with 60MHz bus?

Posted on 2024-04-10, 08:52

by

by MSxyz

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

One thing I find odd is that no chipset manufacturer in the VLB era ever considered implementing the IDE controller inside the chipset for higher performance. That would have made the VLB solely a dedicated graphic port, as it happened with AGP a few years later. Some late 486 chipsets have an …

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Re: How common are graphic cards for the ECS Local Bus?

Posted on 2024-04-09, 09:12

by

by MSxyz

in Marvin \ Video

in Marvin \ Video

ISA does not work at 50 Mhz. It most likely works at 16 Mhz on that board. It works at 8.33 Mhz and the divisor can be set from the BIOS. (CPUCLOCK/6). The board has a single 50Mhz crystal on a socket. Like many early boards, if one wants to mount a different CPU, he also has to change the crystal, …

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Re: Asus VL/I-486SV2GX4 with 60MHz bus?

Posted on 2024-04-09, 08:53

by

by MSxyz

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I recently found a scan of a magazine from 1992 in which they claim the VLB is designed to operate at speeds up to 66MHz. Well, maybe that was the original intention of the designers... I very much doubt it can be done unless the voltage is reduced (i.e. 3.3 - 3.6 V which was already being …

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Re: How common are graphic cards for the ECS Local Bus?

Posted on 2024-04-09, 07:45

by

by MSxyz

in Marvin \ Video

in Marvin \ Video

His 36 MB/s to the graphics card is unrivalled. I believe the bandwidth reported by SpeedSys is not correct. Vspeed reports 6639 KB/s during writes to the frame buffer which is very good for a card on an ISA bus running at 8.33 MHz (ISA bus takes 2 cycles per transaction). EIther speedsys measures …

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Re: How common are graphic cards for the ECS Local Bus?

Posted on 2024-04-09, 06:35

by

by MSxyz

in Marvin \ Video

in Marvin \ Video

Imaginge, how fast it would go with an upgrade. Am5x86 50x3 150 MHz with 3,3 Volt adapter. Well, my intention was more to reproduce the fastest PC available in mid 92. This comes quite close, the only element missing is a card using the ECS local bus. The Genoa Systems 7900 is plenty fast for an …

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Re: How common are graphic cards for the ECS Local Bus?

Posted on 2024-04-08, 16:50

by

by MSxyz

in Marvin \ Video

in Marvin \ Video

Aww... I'll have to find a faster ISA card then! :) I could clock the ISA bus to 10MHz or even 12.5MHz to squeeze a bit more bandwidth, but I'm not a big fan of running things out of spec. Yet, this was the best one could buy in the PC world in late 1991, and a system like this remained top of the …

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Re: Interposer between Cyrix 486 and motherboard

Posted on 2024-04-06, 19:48

by

by MSxyz

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

That's my GitHub repo, and it correctly claims that a "write through" cylce (can be either because L1 is in WT mode or due to a write miss) takes (at least) two clocks. This is an intrinsic property of the 486 bus protocol, unrelated to any Cyrix implementation limitations. You are completely …

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Re: Interposer between Cyrix 486 and motherboard

Posted on 2024-04-06, 15:54

by

by MSxyz

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The reason why the cache is not recognized is possibly explained here: https://github.com/karcherm/cx486wb The 486DLC/S updates the cache in 2 clock cycles in 'write through' mode. If the external cache is of the 'write back' type, and a write cycle also takes 2 cycles, then CACHECHK cannot …

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Re: How common are graphic cards for the ECS Local Bus?

Posted on 2024-04-06, 15:35

by

by MSxyz

in Marvin \ Video

in Marvin \ Video

There's a Gigabyte Local Bus VGA on eBay right now selling for 350€. Oddly enough, a Gigabyte motherboard sporting the same proprietary local bus is selling on eBay only for 200€! Also, I'd love to see a picture of all the three cards produced for this local bus. I remember seeing the ECS VI-833 …

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How common are graphic cards for the ECS Local Bus?

Posted on 2024-04-06, 10:10

by

by MSxyz

in Marvin \ Video

in Marvin \ Video

I've got a nice FX3000 motherboard with a 50Mhz 486 up and running nicely. Unlike many other motherboards of its kind encountered on eBay, this one has the local bus connector soldered. Motherboard is in pristine condition, fit for a collector (and it will end up in a display case someday). …

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Re: Interposer between Cyrix 486 and motherboard

Posted on 2024-04-06, 09:50

by

by MSxyz

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It is, because both in synthetic benchmarks and in applications scores were different with and without cache enabled. I also noticed a small improvement when enabling the Write Back feature, so caches must be working. What I noticed is that CACHECHK also does not detect the 1KB cache of 486DLC ( …

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Re: Interposer between Cyrix 486 and motherboard

Posted on 2024-04-06, 08:43

by

by MSxyz

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The bad news is that the system is a bit underperforming. [...] ... CacheCHK doesn't seem to recognize the 2KB cache at all (see pic). Before working further on this setup, I need to dig up some old utilities for the Cyrix CPUs. The one I used for the 486DLC doesn't appear to be working with the …

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Re: Interposer between Cyrix 486 and motherboard

Posted on 2024-04-06, 08:29

by

by MSxyz

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Quite a lot of 486 boards use chipsets that also support the 386. The bigger issue would probably be the pinout, which I believe is slightly non-standard. Then you'll need a BIOS that can correctly identify the CPU and enable the cache at boot. I've never owned a 486S. Feipoa has one, and I think …

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Re: Interposer between Cyrix 486 and motherboard

Posted on 2024-04-05, 16:53

by

by MSxyz

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The system running about the same speed as a 486DLC kind of makes sense, as it basically is a 486DLC with an extra 1kb internal cache. They were definitely a notch below proper 486s, which is why this product was not very successful. You are right. I dug through all my documentation and datasheets …

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Re: Interposer between Cyrix 486 and motherboard

Posted on 2024-04-05, 09:59

by

by MSxyz

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Good news and bad news for me... :) The "interposer" is indeed a Cyrix 487S FPU. So the CPU is piggy backed on top of the FPU. The bad news is that the system is a bit underperforming. It may be due to the old MB (A Soyo SY-025D1) with an early vlb chipset, but maybe there is more... Even when using …

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