Re: Cyrix 5x86 120GP with Biostar MB8433 Version 2

Posted on 2013-07-18, 17:58

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Yes, the 4 V jumper setting is for use with the trimmer on the voltage regulator. The 3.45 V setting still uses the voltage regulator, but it is fixed at 3.45 V. 5 V feeds directly from the PSU, bypassing the onboard voltage regulator. Jolaes, I was under the impression that rgart was overclocking/ …

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Re: Cyrix 5x86 120GP with Biostar MB8433 Version 2

Posted on 2013-07-18, 10:20

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

No. I think the only way would be to actually test the chip. The cost was not worth the risk. Did the guy ever relist this item? I have some ideas for making 2x/3x chips work at 4x and have ordered the parts, but have not been in any rush to work on it. I seem to have too many little project ideas …

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Re: DTK PKM-0033S +5V pin overheating + PS/2 mouse implementation

Posted on 2013-07-18, 09:07

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I couldn't let this one rest - I decided to test whether or not enabling "PS/2 Mouse Support" in Modbin/Awdbedit is really required to have a functional PS/2 mouse port on the PS/2-capable keyboard controller. I used a 4DPS board as my test subject. The test results proved that "PS/2 Mouse Support" …

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Re: DTK PKM-0033S +5V pin overheating + PS/2 mouse implementation

Posted on 2013-07-17, 21:46

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I originally used a separate inverter package and did place it in the cubbyhole under the keyboard controller, but it still requires rewiring of the existing inverter and keyboard pins. Also, with the inverter under the keyboard controller, the keyboard controller would sit about 1 mm higher. This …

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Re: Cyrix 5x86 120GP with Biostar MB8433 Version 2

Posted on 2013-07-17, 09:05

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Interesting, a 5x86-120 with stepping 1, revision 3. Usually they are stepping 0, revision 5.

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Re: DTK PKM-0033S +5V pin overheating + PS/2 mouse implementation

Posted on 2013-07-17, 05:03

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

More photos...

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Re: DTK PKM-0033S +5V pin overheating + PS/2 mouse implementation

Posted on 2013-07-17, 05:00

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Here are some photos of the final PS/2 job. I wanted to keep the mess on the underside of the motherboard. I was able to use the existing 6-pack inverter IC on the board but had to insulate pins 9 & 10 of the IC so that they do not touch the motherboard through-hole contacts. The original design was …

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Re: Cyrix 5x86 120GP with Biostar MB8433 Version 2

Posted on 2013-07-17, 04:15

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

WBAK, DTE, and MEM_BYP should be on by BIOS default. Maybe LINBRST is too, but it is best to test initial overclocking with LINBRST and BWRT disabled. I do not beleive LINBRST and BWRT did much to the speedsys result. Please refer to the nicely crafted charts and tables in Cyrix Register …

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Re: Cyrix 5x86 120GP with Biostar MB8433 Version 2

Posted on 2013-07-16, 22:23

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

If you want to run the chip stable at 133 MHz, it is best to use an IBM 5x86c. You do not really want to run these chips at more than about 3.85 V. If you are taking it up to 4 V, then you will probably damage the chip with prolonged use. Idealy, we are shooting for 3.7 V. If you are not getting the …

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Re: Cyrix 5x86 120GP with Biostar MB8433 Version 2

Posted on 2013-07-16, 13:48

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Your graphics card is not running at 66 MHz - it is running at 33 MHz. That is what the HOST / PCI clock - 1:1/2 setting is for, to devide the FSB in half for the PCI clock. Try testing with a single stick of 16 MB to begin with. Leave 256 KB installed and ensure it is jumped correctly for 256 KB. …

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Re: DTK PKM-0033S +5V pin overheating + PS/2 mouse implementation

Posted on 2013-07-14, 11:34

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The DTK PKM-0033S uses a SiS 496/497 chipset. There is not a single UMC chip on this board. The IRQ pins on the chipset are directly shorted to the IRQ's on the ISA slot, so I ran the wire to the ISA slot because they are both through-hole solders. Attached is an image of the circuit diagram to …

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Re: DTK PKM-0033S +5V pin overheating + PS/2 mouse implementation

Posted on 2013-07-14, 08:08

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Pins 27 and 39 are wired differently for AT and PS/2 modes. I wonder if this different wiring is all that is required to set the keyboard controller into PS/2 mode. I should try disabling "enable PS/2 mouse support" and see if the PS/2 mouse still works on this DTK board; I did not try this scenario …

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Re: DTK PKM-0033S +5V pin overheating + PS/2 mouse implementation

Posted on 2013-07-13, 22:48

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

For me, it means that I can use one PS/2 mouse for 4 computers on my PS/2 KVM w/audio. Those KVM's with PS/2-to-serial protocal converters have lagged tracking response (they also don't have the audio feature). Also, the smoothness of the tracking of the PS/2 mouse vs. the serial on this DTK board …

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Re: DTK PKM-0033S +5V pin overheating + PS/2 mouse implementation

Posted on 2013-07-13, 08:58

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

PS/2 SUCCESS! - I am now working on integrating the PS/2 circuit onto the motherboard in a discrete manner. Unfortunately, there is only one inverter free on the 7406 so I'll need to use a second 7406 inverter package - EDIT, actually, you can cut the pins off the onboard one and use a single …

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Re: DTK PKM-0033S +5V pin overheating + PS/2 mouse implementation

Posted on 2013-07-13, 08:03

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Here are the HEX values for the 4DPS BIOS, with native PS/2 support: 4dPS-v1.72 410h: 75 47 7C 04 EB 49 E9 55 92 EA 8C 8E 68 3D C6 E2 The original DTK BIOS w/out PS/2 support is: DTK-origl 410h: 44 88 6A 13 BA 38 3c 02 57 26 B6 11 0f 41 89 3D The DTK BIOS using Modbin to "enable PS/2 mouse support" …

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Re: DTK PKM-0033S +5V pin overheating + PS/2 mouse implementation

Posted on 2013-07-13, 04:46

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

SiS 497 pin 8 should be connected to pin 36 of the keyboard controller (MS-OBFO pin). I hope this is the only missing link. On the DTK board, there is no connection here, whereas the 4DPS board has this connection made. I've had to pack my stuff for the weekend, but will re-test this as soon as …

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Re: Smallest 486 MOBO I've seen

Posted on 2013-07-12, 20:00

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

For 100,000 boards, the cost might be more like 1 cent :) I suspect it is because the greater the cache amount the tighter the cache timings become (at least in my experience). They wanted to eliminate the risk of people finding out that more cache = slower timings. This seems very motherboard-, FSB …

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Re: DTK PKM-0033S +5V pin overheating + PS/2 mouse implementation

Posted on 2013-07-12, 19:38

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I beleive the IDE controller is part of the SiS 496/497 chipset duo. I didn't see a 640 chip on the board. The primary IDE port works perfectly fine. The Holtek manual shows different wiring for the keyboard controller for in AT keyboard mode and for keyboard + PS/2 mouse mode. I followed the latter …

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Re: DTK PKM-0033S +5V pin overheating + PS/2 mouse implementation

Posted on 2013-07-12, 10:16

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

So far I have been successful in installing Win98SE and NT4.0 using a PCI SCSI controller. On the other hand, when using the Promise Ultra100 TX2 controller with an IDE drive and you go to shutdown Win98SE, the HDD powers down then up again before displaying "it is now safe to turn off your computer …

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Re: Smallest 486 MOBO I've seen

Posted on 2013-07-12, 09:36

by

by feipoa

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

This work reminds me of the cache rework I did on my HOT-433 v4 board. It came with single-banked 256K soldered on, it was real cache though. The jumper selector header had solder wires, so I also had to solder in jumper headers. Worked fine after the mods, but it makes me wonder why the MB maker …

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