Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-07-10, 11:01

by

by ALEKS

in Marvin \ Video

in Marvin \ Video

root42, one additional question: do I get the right feeling that the card is rendering graphics very slow? Is the PC really slow? Do you happen to know what frequency the ISA bus is running in your machine? For instance, on my 386 DX / 33 MHz, I set the ISA bus speed to 11 MHz and Landmark Speed …

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-07-09, 20:18

by

by ALEKS

in Marvin \ Video

in Marvin \ Video

It looks better already with 270 R. You ae close to getting it stable. I'd say 220 R might be too low. But, let's find out how it turns out while mounted in circuit. PS: Touching the pins alters impedance which is a function of capacitance, resistance, and inductance. So it's hard to pinpoint what …

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-07-09, 06:14

by

by ALEKS

in Marvin \ Video

in Marvin \ Video

pentiumspeed's recommendation is very good (in fact I studied similar books for high-speed PCB design and signal propagation and integrity, which helped a lot for my 80386DX project). The only drawback is that acquiring new skills takes time and involvement. Good thing that you progress with the …

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-06-26, 14:59

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by ALEKS

in Marvin \ Video

in Marvin \ Video

Now that I read it, I think what mkarcher has detailed above is actually what is happening. And that is why increasing the values of RA2 and RA3 allowed for a bigger rise time to make up a "wide-enough" pulse for the refresh circuitry to work properly. This is the most plausible explanation. As I …

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-06-26, 06:45

by

by ALEKS

in Marvin \ Video

in Marvin \ Video

The undershoot (lower bump) is caused mainly by a combination of oscilloscope probe (particularly return signal of probe) and PCB transmission line impedance matching and capacitance adjustment. Slow rise time is caused by resistor array. Once you experimentally go lower then you will be able to see …

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-06-23, 05:25

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by ALEKS

in Marvin \ Video

in Marvin \ Video

My initial prototype is well out of discussion, I guess. For its price you could buy two good ISA cards on eBay. However, root42 has built one with a cheaper PCB after the original schematic. When we manage to get it stable, he would be able to tell the final cost.

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-06-22, 18:22

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by ALEKS

in Marvin \ Video

in Marvin \ Video

Yes it is bad DRAM timing as the refresh signals don't arrive cleanly to the chips. I left you a PM a couple of minutes ago. You need to go lower if the artifacts intensify. In my initial case (starting with my original 22R calculation -- which induced very ugly artifacts -- and then experimentally …

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-06-15, 08:37

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by ALEKS

in Marvin \ Video

in Marvin \ Video

One additional question though. Does your friend also experience 80 x 25 text-mode font tearing as well? Either in standard DOS prompt or RAM manipulating software such as Dos Navigator? I would say he does, but you can check that, to be sure. My assumption is based on the fact that when I was …

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-06-15, 07:58

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by ALEKS

in Marvin \ Video

in Marvin \ Video

That looks strange and indeed very similar to what I was experiencing with /RAS and /CAS small value resistors. I would say, from my experiments, this resembles to a 60R resistor pack. Solder joints should be very finely done (not with big blobs of solder) and thoroughly cleaned of any remaining …

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-06-01, 08:38

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by ALEKS

in Marvin \ Video

in Marvin \ Video

Video DRAM (and other DRAM as well) have /RAS and /CAS lines that are used to constantly refresh the contents of the memory cells. The tracks between the memory controller and the individual memory chips act like high-speed transmission lines. Furthermore, memory chips row and column strobe signals …

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-05-30, 16:40

by

by ALEKS

in Marvin \ Video

in Marvin \ Video

Looks great already. Don't forget about increasing of RA2 and RA3 to reduce artifacts in certain old games.

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-05-15, 11:19

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by ALEKS

in Marvin \ Video

in Marvin \ Video

Great job on fixing the ACL emulation. I found TESTACL.PAS on the UniPCemu repository. I ran it on the real PC and it works great. I will play around with it a bit trying to capture standard output text and display it in ACL mode in 640 x 480 or 720 x 400 graphics mode. By the way, using ACLTEST …

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-05-15, 09:31

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by ALEKS

in Marvin \ Video

in Marvin \ Video

You are absolutely right! I was carried by enthusiasm and forgot for a second how the TurboVision-based programs of back then were writing to the VGA RAM directly. And I think the other DOS shells with proprietary video output implementations such as Norton Commander or Volkov Commander were using …

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-05-15, 06:20

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by ALEKS

in Marvin \ Video

in Marvin \ Video

That sounds like good news! Can you please share the Turbo Pascal code? I was just thinking: would it make sense to write a small TSR that redirects all DOS print character or print string functions through the accelerator? I think a simple hook on the required interrupt vector 21h would be …

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-05-13, 16:42

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by ALEKS

in Marvin \ Video

in Marvin \ Video

With real hardware, on a Pentium 233 MHz class CPU with the ET4000/W32i card, StarCraft should be near real-time in terms of performance.

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-05-12, 17:15

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by ALEKS

in Marvin \ Video

in Marvin \ Video

Then it appears the accelerator emulation code is still somehow faulty. Theoretically StarCraft would not be directly using the video card but would pass through the Windows abstraction layer (including the driver). I had myself some visual pixel artifacts but in my case they were all caused by bad …

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-05-10, 06:08

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by ALEKS

in Marvin \ Video

in Marvin \ Video

I believe that Duke Nukem 3D has a VESA mode optimized for Tseng Labs. But anything using 640x480 in MS-DOS is unplayable with an ISA graphics card. At least nothing that I tried has a decent framerate. Well I played Network Q RAC Rally in 640x480 with this card and it is playable, but the overall …

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-04-22, 08:35

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by ALEKS

in Marvin \ Video

in Marvin \ Video

Vertical retrace IRQ should not be in use on VGA cards. To my knowledge, there is no benefit for enabling it.

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Re: EXCELGRAPH - ISA Video Display Controller (ET4000/W32i)

Posted on 2021-04-15, 12:59

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by ALEKS

in Marvin \ Video

in Marvin \ Video

It might be possible to make an 8-bit ISA variant of the card but I think it is not worth it. This is one of the best ISA card-class video chips and it should be used at maximum potential. An XT machine would barely reach 1 Mb RAM (in most cases having 640 K or less) and small processing power …

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Re: EXCELGRAPH - ISA Video Display Controller

Posted on 2021-04-15, 09:35

by

by ALEKS

in Marvin \ Video

in Marvin \ Video

Yes, CH9294E variant is required in PDIP-20 package. To my knowledge, the G version is mostly in SMD package. And it is not compatible with this design. I think in my case, Windows 98 detected the card as plain VGA as well. I forced the drivers to ET4000/W32i later on.

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