Re: A brief comparison of 386 FPUs

Posted on 2023-06-08, 01:51

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

On another note: Since some 386 and 386SX motherboards allow asynchronous FPU clocks via a separate oscillator, would this allow you to overclock FPUs beyond the CPU/bus speed? Would running them asynchronously have a performance penalty compared to synchronous clock?

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Re: A brief comparison of 386 FPUs

Posted on 2023-06-07, 22:42

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

DOS Tomb Raider 1 (unaccelerated) is an interesting test for FPU performance as well, and a special case for FPU parallelism with an integer based pixel pipeline (or if pixel pipeline isn't technically correct, at least integer/ALU based rasterizer). I haven't found any articles detailing how Tomb …

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Re: Overclocking the Cyrix/IBM 6x86MX PR200

Posted on 2021-09-20, 00:41

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Refreshing my memory with datasheets (and looking over some I hadn't before), Cyrix, IBM, and NSs split-rail voltage Socket 7 parts (from 350 nm all the way out to the 180 nm PR433) share the same absolute maximum ratings on the datasheets: 4.0V for VCC3 (that would be the I/O voltage) 3.3V for VCC2 …

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Re: Overclocking the Cyrix/IBM 6x86MX PR200

Posted on 2021-09-19, 05:11

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I stumbled on this when looking for any discussions on IBM 6x86MX vs Cyrix MII processor overclock (or undervolt) performance, but don't really see any on that topic. I haven't had a large enough sampling to fully compare, but the National Semiconductor produced CPUs all seem to have some …

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Re: M396F motherboard

Posted on 2021-09-12, 21:44

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The strange memory speed losses seen in some 386DX boards earlier in this thread could also be from boards using WB cache without a dirty bit, so main memory speed drops with cache enabled. Also note some 32-bit bus systems were being seen as 2-bytes wide instead of 4-bytes wide in cachecheck, so …

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Re: The World's Fastest 486

Posted on 2021-08-29, 07:48

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Well, I was playing around with my C4PI Rev A01 motherboard and the one AM5x86 I have that does 180 MHz reliably (doesn't need much overvoltage either, 3.5V seems fine, and will also do 160 at 3.1V). It's an SiS 496/497 board that supports 3.1 to 4.0V (plus probably a 5V setting I don't know) and …

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ATi 3D Rage (Rage I Mach64 GT) running Unreal?

Posted on 2021-08-20, 09:28

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I ran across this video and am a bit puzzled by the portion with Unreal (or at least the castle flyby demo) running with what looks like proper lighting effects. https://www.youtube.com/watch?v=wXKMxNg-_0Y At 22:27 they show Unreal running, and not with the typical broken/missing light maps and …

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Re: FX-3000 motherboard thread

Posted on 2021-07-29, 03:25

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

mine lacks the VLB header It's one of those early "local bus" slots, which were made before VESA standard was set in stone. Technically it's the same thing, but not electrically compatible. Yeah, good thing I didn't end up with one of the examples with a local bus slot included or I might have …

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Re: K6-2/3+ Success on Asus P5A 1.06 - simple mod

Posted on 2021-07-14, 04:34

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

There's also been some "oddness" going on with Vcore jumper settings. Even though I'm using a K6-2+ with a nominal Vcore requirement of 2.0v, I've discovered that I need to set the jumper position to 2.1v to get the board to post and boot. At 2.0v the system will not boot with a K6-2+550. Not …

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Re: FX-3000 motherboard thread

Posted on 2021-06-12, 06:20

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I've got one of these (with the US 3486 branding) along with the manual. There might be some additional documentation in the manual not floating around already. I may be able to scan/photgraph mine for archive purposes at some point. It's the same UMC based 3486 board I referenced a few times last …

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Re: Advanced Computer Technology 35-7024-00-00 + Harris CS80C286-25

Posted on 2020-06-08, 20:40

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

https://stason.org/TULARC/pc/motherboards/U/UNIDENTIFIED-286-EAT-12.html The DIP switches may be for DRAM bank size and wait state configuration like some older ACT 286 boards. Switch 4 may be the WS control switch on your board as well. In which case, yours is set to 1WS (switch on = 1WS, off = 0WS …

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Re: Kixs's 286 to the Max

Posted on 2020-06-08, 20:27

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by kool kitty89

in Marvin \ System Specs

in Marvin \ System Specs

The DIP switch settings (and maybe some jumper settings) may be similar to some of the other (probably older) ACT chipset 286 boards. There's at least one on the Stason website, the EAT-12 https://stason.org/TULARC/pc/motherboards/U/UNIDENTIFIED-286-EAT-12.html The DIP switch block there configures …

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Re: ISA based 3D accelerators?

Posted on 2020-06-08, 19:41

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by kool kitty89

in Marvin \ Video

in Marvin \ Video

@SteveC @Jo22 Yes thanks. Matrox ftp does have PG-XXXX files, which I already had, but can't find anything on SM-XXXX series (iirc thats why I contacted Matrox UK). I may have to revisit this as a summer project this year. Here are some low-res images (dug out of my piccyes folder, cards are in …

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Re: TI 486SXL and 486SXL2 PGA168 on socket 3 motherboards

Posted on 2020-06-08, 09:46

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It doesn't seem like avoiding making a full 486 as much as having the existing 486SXL core available (and having expanded the Cyrix 486DLC from 1kB to 8kB L1 cache) and simply producing it in the PGA-168 form factor. I'd assume the logic was to be compatible with boards very similar to existing 386/ …

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Re: Cyrix appreciation thread

Posted on 2020-06-08, 09:39

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Not the 87DLC, sorry I'd meant the Cyrix 487S, which I've only seen in QFP-80 form and either mounted directly on a 486 motherboard next to or inside the PGA socket or on a PGA-168 interposer like this: http://www.x86-guide.net/en/fpu/Cyrix-487S-40-cpu-no3800.html I'd thought they might work with …

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Re: The World's Fastest 486

Posted on 2020-06-08, 09:16

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Correction to any previous reference I made to the MB3486 motherboard. I got my wires crossed: it's a US 3486 board (based on the manual naming). The UMC chipset listed is correct, but it's not a Biostar board. I've also gotten an Intel 486SX-33 to run at 66 MHz in it with similar results to the DX- …

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Re: Cyrix appreciation thread

Posted on 2020-06-07, 09:06

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Judging by some of the experiences recounted in this thread: https://www.vogons.org/viewtopic.php?f=46&t=60600 It seems like it's only Cyrix-derived 486S or SXL type CPUs that are likely to work with the 487DLC external coprocessors on interposer boards, and normal 486SX type CPUs from Intel and AMD …

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Re: TI 486SXL and 486SXL2 PGA168 on socket 3 motherboards

Posted on 2020-06-06, 10:59

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I've got a TI 486SXL-40 that was purchased as-is several months ago and so far haven't gotten to POST. It's in good cosmetic condition and I assumed it wasn't dead, but it's failed to POST in the several boards I've tried it in. (starting with my OPTi 495SX based 3486 board then a Soyo SiS 471 and …

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Re: The World's Fastest 486

Posted on 2020-06-03, 12:22

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I still need to post pics related to the last few updates, but I dug into a Biostar MB3486 with UMC UM82C481/482 chipset. While it annoyingly seems to have no parity disable option, finding stable configurations with parity errors in mind isn't that much more difficult and I don't have that much …

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How common was it for motherboards up to the 486 era to have a parity disable option?

Posted on 2020-06-01, 15:19

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by kool kitty89

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I'm pretty sure most or all IBM boards and a lot of name-brand OEM systems forced parity checking while some XT clone boards and a lot of older 286 boards have the option selectable by switches or jumpers and late gen 286 boards usually offer it in the BIOS. Then there's a handful of 8088 and 286 …

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