Re: Cyrix appreciation thread

Posted on 2023-03-26, 09:45

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

So where I was coming from was that the memory mapped i/o mode debuted on the EM87 Do you have a reference for a memory-mapped I/O mode in EM87? The only "EM87" I could find connected to coprocessors is a public-domain TSR described from example in https://www.vogonswiki.com/images/2/21/Coproc.txt …

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Re: Cirrus Logic GD5429 VLB significantly slower than a TSENG ET4000

Posted on 2023-03-25, 21:46

by

by mkarcher

in Marvin \ Video

in Marvin \ Video

The Local Ready delay = none and a 70MHz memory clock really brought the Cirrus up to very near the performance of the TSENG ET4000. I wouldn't call it "the Cirrus is near the performance of the ET4000", because raw throughput is still less than 50% of the ET4000 (which is not surprising), but on …

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Re: OPTI-495SLC 386 WB mainboard fails to POST when powered up but POSTs after reset

Posted on 2023-03-25, 21:29

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

This might explain the behavior and is in line with the above mentioned fact that reset LED is not showing anything. I will investigate it further. Any further hint what particular circuit might be responsible for this is welcome - I did no find schematics for the board yet. Typically, those …

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Re: OPTI-495SLC 386 WB mainboard fails to POST when powered up but POSTs after reset

Posted on 2023-03-25, 09:23

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It has some damage due to battery leak that I have cleared. I measured affected wire patches and they seems to be OK. The damaged part is shown on the attached picture. The board often fails to POST when I turn the PSU on. When I press reset button the board boots normally in 100% of cases. My …

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Re: I let the smoke out of a Pro Audio Spectrum 16. Can it be repaired and saved?

Posted on 2023-03-25, 09:09

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It died the instant I put it in. (...) I want to be safe and not break the card any more than I already have. FYI it's not your fault. These older tantalum caps can die like that, especially after a long period (years) of not being powered. Just to add to that perfectly correct analysis: If your …

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Re: Cyrix appreciation thread

Posted on 2023-03-25, 08:45

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

What do I mean? Well when Cyrix brought out a memory mapped and i/o mapped capable version of the x87, which original 83D87 didn't support, in the next iteration of the 83D87, they apparently rolled it in... and some indication they carried it through to all of their x87 class hardware thereafter …

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Re: Cirrus Logic GD5429 VLB significantly slower than a TSENG ET4000

Posted on 2023-03-22, 00:27

by

by mkarcher

in Marvin \ Video

in Marvin \ Video

mkarcher, I gave your clmclk a try and it is reporting the current MCLK at 50.12 MHz. Upping it to 60MHz gets me a bandwidth of 8437KB/s (up from 7672 KB/s). What should I look for in the BIOS? My motherboard is a PC Chips M912 v1.7. It used to have fake cache, but now it has 512K of real cache. My …

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Re: B/W VHS - possible or not?

Posted on 2023-03-21, 21:14

by

by mkarcher

in Milliways

in Milliways

I'm wondering if it was possible to record pure monochrome signals (luma) via VHS. By pure, I mean without recording any chroma information on tape. Of course it was technically possible to skip recording the color signal. Every VHS recorder had to separate chroma and luma from the CVBS (composite) …

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Re: Cirrus Logic GD5429 VLB significantly slower than a TSENG ET4000

Posted on 2023-03-20, 22:54

by

by mkarcher

in Marvin \ Video

in Marvin \ Video

The complete CL-GD542x series only has a 16-bit bus interface. It uses the VLB signal to tell the processor: "I only handled 16 bits. If this was a 32-bit request, please repeat the request for the high 16 bits". That's the BS16 (Bus size: 16) signal. This alone causes some slowdown. Furthermore, …

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Re: Evergreen 586 & Biostar MB-1433/50UCV-E

Posted on 2023-03-20, 22:39

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Thanks for all of your help. It runs like a champ! I can actually sort of play Quake 😄 and Doom runs about as well as it can. Is there much risk of damage with a 17MHz overclock? Don't worry about the overclock. A lot of people are running the 5x86-133 at 160MHz constantly, and were already doing …

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Re: Finally got my grubby little hands on a real SB Pro 2.0

Posted on 2023-03-19, 10:29

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by mkarcher

in Marvin \ Sound

in Marvin \ Sound

If https://github.com/joncampbell123/dosbox-x/blob/master/src/hardware/sblaster.cpp#L1982 is faithful to the real hardware, ESS cards (starting at the ESS688, so basically anything with stereo support) automatically programmed their software-controllable low-pass filter to 80% of the Nyquist …

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Re: Evergreen 586 Driver Disk

Posted on 2023-03-19, 10:15

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The cache on the AMD 5x86 is hardware controlled only. You can't toggle between write-back and write-through mode using software. Drivers to enable WB cache is only a thing on Cyrix/IBM/ST processors, both the 486 series, as well as the 5x86 and 6x86. Thank you, I guess my understanding was wrong. …

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Re: Evergreen 586 Driver Disk

Posted on 2023-03-18, 22:05

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

both of which do not detect my AMD 5x86 upgrade. I would like to enable the WB cache, which to my understanding only works with the provided driver loaded. The cache on the AMD 5x86 is hardware controlled only. You can't toggle between write-back and write-through mode using software. Drivers to …

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Re: I let the smoke out of a Pro Audio Spectrum 16. Can it be repaired and saved?

Posted on 2023-03-18, 08:39

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

And on top of replacing the four next to the ISA edge connector, should I replace *all* of the tantalums on the board? There are 16 on the board and I can see the values on 15 of them. Those 16V tantalums mostly explode when they are old and suddenly get 12V. If should be sufficient to replace …

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Re: 486 board with UMC 8881E/8886B: The winner is: EDO without L2 (terms and conditions apply)

Posted on 2023-03-17, 23:41

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Thank you for the description. Where did you optain that 200 uF value? I guessed from what I saw near the processor socket. There are four capacitors in a case size that is typical for caps of 22µF or 47µF, so I guessed 200µF for four of them (assuming they are all on Vcore, not on +5V) to be on …

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Re: Compaq Prosignia 3080 / 486DX33

Posted on 2023-03-17, 23:20

by

by mkarcher

in Marvin \ System Specs

in Marvin \ System Specs

It is a while since i worked on this machine the last time, but I had it started a few months ago and it still works great. When I started my ProSignia 3080 a couple of years ago (after 12 years of storage), all tantalum caps on 12V rails (three on +12V, one on -12V) failed with fireworks and smoke …

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Re: Is there any ISA sound card that only needs +5V

Posted on 2023-03-17, 08:16

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by mkarcher

in Marvin \ Sound

in Marvin \ Sound

The main point of sound cards using +12V (and sometimes -12V) is for the analog audio amplifiers. There are very cheap but sufficiently good general-purpose amplifier chips ("operational ampliefiers") that can not process signals exceeding 2V below the positive power supply or 2V above the negative …

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Re: 486 board with UMC 8881E/8886B: The winner is: EDO without L2 (terms and conditions apply)

Posted on 2023-03-16, 19:09

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

On all my MB-8433UUD boards, I have added a trimmer to the 4V option of the jumpers to allow for variable CPU voltages. I am wondering if it would be suitable to merely short this diode, D15, thus allowing for higher voltages to overclocked CPUs? It would be easy enough to add the protection diode …

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Re: Rotating the Chill and Phil midi adapter for a smoother finish

Posted on 2023-03-16, 06:38

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by mkarcher

in Marvin \ Sound

in Marvin \ Sound

today I pulled the case out and the CHILL and PHIL unit is no longer working with my AWE64Gold. [...] Issue is likely related to my AWE64Gold or some system other compatibility/conflict. Is the CMOS battery flat in that system? If yes, you might have lost settings and activated the MIDI interface …

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Re: Identifying specific RAM ICs for Pine PT 524/8G VLB card

Posted on 2023-03-15, 20:37

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The cirrus cards do not get faster with the second megabyte equipped. You get more offscreen memory for accelerated drawing, and the card will have enough memory for 1280*1024 with 256 colors and 1024*768 with 65536 colors. In both cases, the Cirrus chip is too slow to show these modes at 60 Hz, so …

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