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

Posted on 2023-04-05, 07:39

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Now, that's funny. I had no issues with 2-1-1-1 at 40MHz on the Biostar board and RAM WS 0/0 with the 5x86. I did need 1/0 on RAM WS to get stable operation on the HOT-433 with an earlier 8881 revision, though. This is correct, 2-1-1-1-1, 0ws/0ws, 40 MHz, cx5x86, and 256K is not an issue, even with …

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Re: Help wanted --> ALI M1429/M1429G : Need peoples with M1429 board that have a BIOS for adult to dump chipset register

Posted on 2023-04-04, 17:55

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I downloaded the Award BIOS 2.0 for the A-Trend 1762 from The Retro Web, I will try to dump the setup table from it, which should directly yield a mapping of CMOS options to chipset bits. Great, that should speed the thing up if that work! Thanks I found the following settings: 12 10: Hidden …

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Re: Help wanted --> ALI M1429/M1429G : Need peoples with M1429 board that have a BIOS for adult to dump chipset register

Posted on 2023-04-04, 16:45

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I downloaded the Award BIOS 2.0 for the A-Trend 1762 from The Retro Web, I will try to dump the setup table from it, which should directly yield a mapping of CMOS options to chipset bits.

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

Posted on 2023-04-04, 16:40

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The CY7C1009D has the "classic" pin layout the DIL chips had, but these chips are increasingly hard to find. If you can manage to adopt your PCB-layout to the later pinout (with Vcc pins at the center) sourcing the chips would be far easier in the future. Are you talking about the CY7C1049G for …

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Re: VGA cards with little RAM (256KB): Why were they made in first place

Posted on 2023-04-04, 14:09

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by mkarcher

in Marvin \ Video

in Marvin \ Video

So making a video card perform acceptably at 320x200 in 256 colours was already quite difficult, and VGA cards in the early days were notoriously expensive. For higher resolutions you'd need much faster VRAM (and VRAM tends to be more expensive than regular system ram, as you need dual ported ram …

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

Posted on 2023-04-04, 11:55

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

My statement was only to serve as an agreement - ensure the PCB can be used for 1024K double-banked and 512K double-banked, which it seems like you are planning for. Yes, 512K with A19 grounded, pulled to 5V (directly or using a 10K resistor) makes an plug-and-play experience to get to 512K without …

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Re: midi modules using 12v instead of 15v? or 9v for 10v?

Posted on 2023-04-04, 11:30

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by mkarcher

in Marvin \ Sound

in Marvin \ Sound

If a MIDI module contains internal voltage stabilization using linear regulation, it requires a minimum voltage for the regulator to be able to provide a stable output voltage. Going lower will cause more noise in the synthesized music. As linear regulators are converting the excess voltage into …

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

Posted on 2023-04-04, 10:42

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Yes, I think it would be good if your PCB can be easily adapted to 512K, assuming these 10 ns SOJ chips are still available. I already included the resistor on CPU A19 / Cache A16 / Tag A15 into the design that will become "v1.0". And as I said, it's easily bodged on in the prototype design, and …

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Re: VGA cards with little RAM (256KB): Why were they made in first place

Posted on 2023-04-04, 08:27

by

by mkarcher

in Marvin \ Video

in Marvin \ Video

The question is: So why do early VGA cards, IBMs original and the clones do have a lumpy 256KB that's useless for anything except what we call "Standard VGA"? You know, that pseudo NTSC TV resolution with merely a nibble of colour. ;) The answer is quite simple: It was considered good enough for …

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Re: Overclocking a TI486DX2

Posted on 2023-04-04, 07:39

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

3 - Jumper JP12 must be positioned depending of what the bus is running at. one position for 25/33 and one for 40/50 Many 486 boards have a jumper like that, especially if they have VL slots. There is a pin on the VL slot that is intended to inform cards whether they got 1 clock cycle to claim a …

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

Posted on 2023-04-04, 07:16

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It has been about 8 years since I have looked into this modification. In preparation for this modification, I looked at the convention used on 3 or 4 other motherboards for 1024K. In my MB-8433UUD manual, page 8, which describes the details for this cache mode, I have noted: 4) Solder in a 10K SMD …

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

Posted on 2023-04-04, 00:04

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I will be interested to see if this works well. In looking at your board, I don't see the 10K resistor to be used on TAG A15 and A16. Why would you need resistors on the TAG address bits? This board is not meant to be adaptable to different cache sizes, it only works with 9 chips of 128k x 8. So …

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

Posted on 2023-04-03, 23:42

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Wouldn't you want to use all the motherboard's female cache sockets to connect to the male pins on the PCB, even if unused, for increasing hold-on strength? It connects into all sockets, but not into all pins.The pins to connect to the sockets are through-hole. The SOJ chips don't fit mechanically …

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

Posted on 2023-04-03, 23:26

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

feipoa wrote on 2023-04-03, 23:09: How does this PCB connect to the MB-8433UUD? The pins on the "back side" should be IC header pins (round, thinner than displayed) and they plug directly into the cache sockets of the board. All signals and power is taken from the cache sockets, except for A19, …

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Re: Overclocking a TI486DX2

Posted on 2023-04-03, 21:52

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

And see no trace of messing with index register 1Bh, which if is the same in M1429 than M1489, would mean that it would use default of slow timing for read and write, disable RAS only refresh, disable onboard parity check and 4T for CPU time slot (I don't know what that latter is). Next step would …

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Re: Overclocking a TI486DX2

Posted on 2023-04-03, 21:41

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Here are the documentation : https://stason.org/TULARC/pc/motherboards/A/ACER-INC-486-ACERMATE-486-G-A1GX-2.html Note that 50Mhz fsb is not on the documentation nor on the board silkscreen, found it by mistake because the 40mhz jumper setting was corroded and not making contact initially (JP11 not …

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Re: Detecting if a CPU is an AMD Am486 or an Intel i486 from within Windows

Posted on 2023-04-03, 21:29

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

https://learn.microsoft.com/en-us/windows/win32/api/sysinfoapi/ns-sysinfoapi-system_info , FFD0 means: Model 3, Stepping 0. I just looked at https://www.sandpile.org/x86/cpuid.htm and there are several 486 models > 5 namely as below. I wonder how these are reported. I am pretty are all the Intel …

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Re: Detecting if a CPU is an AMD Am486 or an Intel i486 from within Windows

Posted on 2023-04-03, 18:45

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I wonder how they distinguished a stepping D 486 CPU: https://www.betaarchive.com/wiki/index.php?title=Microsoft_KB_Archive/103933 Perhaps just by testing for the bug that affected stepping C and if it isn't buggy, it must be D? I'd guess there is no stepping D 486 CPU without CPUID, making the …

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

Posted on 2023-04-03, 18:20

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

What is your source for CY7C1009BN? I don't see this P/N on mouser or digikey. Looking forward to you (eventual) SRAM gadget. That chip has been superseeded by the CY7C1009D. I see it offered for ~3,60€ / piece (at qty 10-100) on Mouser (in stock!) at the 10ns speed grade. While that price is not …

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Re: Detecting if a CPU is an AMD Am486 or an Intel i486 from within Windows

Posted on 2023-04-03, 17:47

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I keep hoping the BIOS will pass the information into Windows NT and the SYSTEM_INFO->wProcessorRevision; returned by GetSystemInfo() will be sensible. It's FFD0 for my Am486 DX2-66 and need to gather information for other CPUs that don't have CPUID. According to https://learn.microsoft.com/en-us/ …

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