Re: How can a floppy disk have a sector size of 8192? (re: Sierra AGI; Superlok protection)

Posted on 2023-10-14, 16:20

by

by mkarcher

in Marvin \ Software

in Marvin \ Software

I understand the floppy disks can contain sectors of different sizes, but in the example of the Sierra AGI disks, track 6 contains the following sectors: Sector 1 = 8192 bytes Sector 2-8 = 1024 bytes That's a total of 15,360 bytes or 15 KB for that track. If I understand correctly, typical 3.5" …

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Re: The Soundblaster DSP project

Posted on 2023-10-13, 20:22

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

yep, it seems that way, using 'Debug.exe' for the test - i shouldn't do '-o 331 ac' and then immediately '-i 330', but after '-o 331 ac' do several times '-i 331' until those bits are in correct value and then do '-i 330'. If you are manually typing into debug, it is very unlikely that you need to …

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Re: The Soundblaster DSP project

Posted on 2023-10-13, 20:18

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Well, obviously you technically can read the MPU data port (0x330) even if the DSR bit in 0x331 is not set cleared. That's what mattw did all the time. But it makes no sense to read the data port when the DSR bit not set. The key point is that the DSR bit tells you whether the data you obtain at …

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Re: How can a floppy disk have a sector size of 8192? (re: Sierra AGI; Superlok protection)

Posted on 2023-10-13, 17:04

by

by mkarcher

in Marvin \ Software

in Marvin \ Software

Sector 1 does have a sector size of 8192 but how is that possible? The sector header contains a byte that indicates the data size of the sector. It's encoded like sector_size=2^(size_code+7) bytes. So if the size_code in the sector header is 2 (the usual value), the sector size is 2^9 (^ means …

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Re: Is there any reason to install more than 1 MB RAM on a 286 PC?

Posted on 2023-10-12, 23:03

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

With the AT, IBM realized that they had to extend to 16 bits, and the AT works fine as 16-bit 80286 machine. If you don't insist to run outdated 8086 software on it, but go "native 286", you don't have to deal with the A20 gate (A20 can be enabled all the time), you don't have to deal with resets …

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Re: AWE32 not working

Posted on 2023-10-12, 22:00

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

If that AWE32 is a non-PNP model, Windows would not detect it by default. You would have to manually install it using the "Add New Hardware" wizard. And if the AWE32 is a PNP model and Windows doesn't detect it, the PnP information may be damaged. There are two helpful threads here on VOGONs that …

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Re: Is there any reason to install more than 1 MB RAM on a 286 PC?

Posted on 2023-10-12, 21:52

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

With CGA graphics, 16 or 64 KB of RAM, ROM BASIC, the cassette interface and lack of an HDD it was specced more like a home computer, still. Or in MDA configuration, the equivalent to an electronic typewriter with a disk drive (similar to the Wang and Olivetti models). As I heard the story, the …

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Re: Is there any reason to install more than 1 MB RAM on a 286 PC?

Posted on 2023-10-11, 18:54

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Great write up. Can I talk you into giving your version of the classic story about A20, himem, and the keyboard controller? Yeah, but be prepared for some unpopular oppinion mixed in it. When Intel designed the 80286 processor, they didn't specifically target the IBM PC, and especially, Intel …

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Re: The Soundblaster DSP project

Posted on 2023-10-10, 19:37

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Maelgrum wrote on 2023-10-10, 19:25: no timer should be used for the task, and timer is not needed,as ExtInt0 interrupt is synchronous to samplerate (triggered at samplerate speed) you can simply output one sample per ExtInt0 interrupt Thank you! That's the clue I was missing.

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Re: The Soundblaster DSP project

Posted on 2023-10-10, 19:17

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I'm unsure whether this will work at the expected quality. The SB/SBPro uses a classic R/2R-type DAC which is quite resistant to jitter. On the other hand, the SB16 uses an Sigma/Delta DAC (aka Delta/Sigma DAC), which requires to process samples exactly at the sample clock. This is why you should …

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Re: The Soundblaster DSP project

Posted on 2023-10-10, 17:00

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

My idea is do this in SB/SB Pro way - not hardware assisted. I'm unsure whether this will work at the expected quality. The SB/SBPro uses a classic R/2R-type DAC which is quite resistant to jitter. On the other hand, the SB16 uses an Sigma/Delta DAC (aka Delta/Sigma DAC), which requires to process …

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Re: Is there any reason to install more than 1 MB RAM on a 286 PC?

Posted on 2023-10-10, 16:48

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

...The "virtual 8086 environment" provided by EMM386 is slightly slower than running the 386 in real mode... Wait... what what? What's this virtual environment and this 386 real mode??? Short version: The 8086 processor just has a single mode of operation, and when the 286 processor introduced a …

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Re: Where to obtain 110 MHz RAMDAC for ARK1000VL graphics card?

Posted on 2023-10-10, 15:58

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

mkarcher, your response sheds a glimmer of hope. Would you be interested in working on such a VGA BIOS hack? I can try to prepare a patch that replaces the 1024x768x64k interlaced mode by an overclocked non-interlaced mode. Please don't hold your breath, though. If that patch is successfully, I …

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Re: Is there any reason to install more than 1 MB RAM on a 286 PC?

Posted on 2023-10-10, 07:08

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

"Static column" technique. Not static ram memory. I think the article meant fast page memory chips. Static column RAM is slightly different from FPM RAM. FPM RAM dominated the market in the end, and static column RAM was a only used in a small number of "mainstream" computers. With FPM RAM, you …

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Re: Universal chipset patcher. Initial release

Posted on 2023-10-10, 06:56

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by mkarcher

in Release Announcements

in Release Announcements

As you said, you need to program something to flush the cache, because ctchip can't do it.... Actually, ctchipz can do it. Some cfg files contain "macros" that perform different operations in sequence. Flushing / reloading the cache is available in macros. There is a bug in the reload code if you …

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Re: AT power supply 12V is low

Posted on 2023-10-09, 19:15

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

After messing a bit more around with this power supply I think I know now what killed Q1 in the beginning. I didn't realize but the 2625's are not insulated from the heat sinks. Found this out by brushing my hand up against one of the heat sinks when it was on. Gave me a good little buzz. Testing …

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Re: Is there any reason to install more than 1 MB RAM on a 286 PC?

Posted on 2023-10-09, 19:00

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I do vaguely remember from the Pentium days that a higher amount of RAM could sometimes lead to lower performance, due to the cache (COAST) module not "covering" all of it. Or maybe I remember it incorrectly or incompletely? Yes, this is true. The issue of a limited cachable area existed in on- …

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Re: Where to obtain 110 MHz RAMDAC for ARK1000VL graphics card?

Posted on 2023-10-09, 07:21

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

mkarcher, I received a PM about trying to force this ARK1000VL card into 1024x768x64K mode at 56-60 Hz. Do you think it is possible to accomplish this if running VCLK at 130 MHz (the max the PLL can output), increasing MCLK, and altering the VGA BIOS? Obviously this will overclock the CRTC / Shift …

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Re: The Soundblaster DSP project

Posted on 2023-10-08, 12:43

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

it looks like Creative totally cheap-out, since its PAL (i.e. programmable) chip, it seems they had old re-marked chips left-over from CT2290 cards and reprogrammed them. The custom marked PALs usually are OTP or mask programmed, so they can't be re -programmed. To me, it looks like the chip is not …

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Re: Is there any reason to install more than 1 MB RAM on a 286 PC?

Posted on 2023-10-07, 20:21

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I may have picked it up wrong even at the time but I remember For Dummies books and the like portraying Compaq as coming with a clever hack with CEMM to provide EMS on the Deskpro 386, followed by the various EMM programs that followed. That's the same story I heard, and I think it's plausible. …

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