Re: AT power supply 12V is low

Posted on 2023-09-30, 19:25

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Well went from bad to worse. I checked the two ends of C2588/02C and had 32 volts on one leg and 58 volts on the other, Those values sound completely off. One would expect a reading of zero volts in DC mode, or maybe a slightly negative voltage (like -0.8V) there, because it is AC. If you measure …

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

Posted on 2023-09-30, 17:51

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The screen still jitters at 1280x1024x256c at 60 Hz, but it jitters in a different manner compared to how the non-edited BIOS was jittering. The "60Hz jitter" looks like an issue with the memory clock. Either the memory clock is too high for the memory chips, so they can't provide data fast enough, …

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Re: AT power supply 12V is low

Posted on 2023-09-30, 17:32

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Open diode on the 12V rail would cause pretty high drop and a lot of ripple. Check the soldering too, could be cracked solder somewhere. Good advice. The +12V rail in this supply is rectified by the heatsinked double-diode D22 (behind R40), labelled "C2588 / 02C". There are two 12V AC output pins …

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Re: What was the first ever smooth 70 Hz hardware scrolling DOS game?

Posted on 2023-09-29, 19:44

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by mkarcher

in Marvin \ Software

in Marvin \ Software

I do believe Supaplex was intended to run at 35 Hz, and the 70 Hz rate was more of an accident on 386+; the game first does its calcs, then waits for vsync to scroll, so the framerate is doubled on any machine that can manage the first part in less than one frame. It's not really clear what …

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Re: All Cirrus Logic VLB cards capable of working @ 50 MHz with 0 wait states?

Posted on 2023-09-29, 19:34

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by mkarcher

in Marvin \ Video

in Marvin \ Video

every Cirrus Logic GD542x VL-Bus graphic card works with: FSB @ 50 MHz 0 wait states The sheet is clear: http://www.elemar.pl/PDF/CL-GD5422.pdf That's not how data sheets work. The chip can work at 50MHz FSB, and the chip can work at 0 wait states. The "banner specs" do not necessarily mean that …

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Re: Does any of these 486 CPUs exist with Write-Back L1 cache?

Posted on 2023-09-29, 18:56

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

As per title question: • Intel 486 DX2 66 • AMD 486 DX2 80 • AMD 486 DX4 120 Any of them with write-back L1 cache? Thanks Yes, all of them do exist. Both Intel and AMD sold a lot of 486 processors to embedded system manufacturers when PC users already used Pentium and newer processors. These …

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Re: Good VLB card benchmark

Posted on 2023-09-29, 18:51

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Technically, this would be matter for reimbursement / returns requests, heck even class-action lawsuits. Because the real specs of the products did NOT match what was advertised and declared on the spec sheets. You are looking at a graphics chip datasheet that is targeted to professional graphics …

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Re: Showing some love for Adaptec's ugly ducklings: Adding big drive support to EISA and VL controllers

Posted on 2023-09-29, 18:27

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Are you suggesting I just hex edit the partition type field in the table and change nothing else? Should that work normally? Yes, exactly that. As long as the CHS and LBA fields in the partition table are consistent, and you don't change a partition that exceeds the CHS boundary (i.e. 8GB with the …

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Re: Showing some love for Adaptec's ugly ducklings: Adding big drive support to EISA and VL controllers

Posted on 2023-09-28, 21:33

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The BIOS decides whether to do "extended translation" (X/255/63) or regular (X/64/32) translation based on whether the total drive size is >1GB right? So wouldn't the CHS calls need to process the total drive size for that reason? Even if that was only done once at the time of enumeration, if it …

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Re: Strange SIMM ram package

Posted on 2023-09-27, 23:18

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Of course the ultimate example of UK use of partially defective chips (in the early eighties) was Sinclair's computers. The Spectrum was specced to use 32kb chips, but frequently was built with half-defective 64kb chips instead. No wonder these machines were so much cheaper than competitors... Did …

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Re: Showing some love for Adaptec's ugly ducklings: Adding big drive support to EISA and VL controllers

Posted on 2023-09-27, 23:11

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I guess we kinda already knew this, but whatever the problem is with this 73GB drive on this system is specific to the CHS type int 13 calls. If I partition/format it with a single 100% FAT32 partition it actually works fine. The format will crash at the end as shown in my screenshot before, but …

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Re: Showing some love for Adaptec's ugly ducklings: Adding big drive support to EISA and VL controllers

Posted on 2023-09-26, 17:27

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

As for Aspi - my SCSI drive has died (like lots of others before). I ordered a party of newer ones and will try them instead. Then I can tell more about Aspi7DOS.sys problem. Just a ping to you (by quoting you). The ASPI7DOS problem has been identified and fixed by now. Also, the BIOS patch before …

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Re: Showing some love for Adaptec's ugly ducklings: Adding big drive support to EISA and VL controllers

Posted on 2023-09-25, 20:27

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It appears to format just fine until the very end, after I enter the volume label it hangs with the drive LED stuck on. By the way, I found out when it does this it will eventually timeout (after like over a minute) and give this error. It's not a hard system lock, though the LED remains stuck on …

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Re: Setting Chinon FD-502 5.25 drive as B:

Posted on 2023-09-25, 20:11

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Thanks for all suggestions, serting it at DS1 and opening TERM makes it run flawlessly as B: in the middle of the cablw but onky when there is an A: drive after the twist at the end! Very curious! "only whene there is an A: drive" is not that surprising: You need a drive to terminate the bus. So if …

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Re: Setting Chinon FD-502 5.25 drive as B:

Posted on 2023-09-25, 18:56

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I have Chinon FD-502 that is content with running as A in the middle of a floppy cable but does not work as B on either position. Jumper settings are TERM Closed DS0 Closed DS1 Open DS2 Open DS3 Open That's actually a quite interesting scenario: The PC floppy drive systems uses a "twist" on the …

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Re: Tandon TM-100-2A floppy drive: head moves to track 39 (not 0!) and stays there

Posted on 2023-09-25, 17:42

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

A floppy drive is not supposed to seek on its own. It should only seek when it receives pulses on the "STEP" line. If a drive moves the head either direction, it looks like the STEP signal is picking up noise (like 50/60/100/120 hz hum), and causes the drive to step at that rate. The "DIR" pin …

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Re: Showing some love for Adaptec's ugly ducklings: Adding big drive support to EISA and VL controllers

Posted on 2023-09-25, 06:16

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

It appears to format just fine until the very end, after I enter the volume label it hangs with the drive LED stuck on. By the way, I found out when it does this it will eventually timeout (after like over a minute) and give this error. It's not a hard system lock, though the LED remains stuck on …

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Re: Showing some love for Adaptec's ugly ducklings: Adding big drive support to EISA and VL controllers

Posted on 2023-09-24, 20:24

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by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

The test I did with the 73GB drive was very simple yesterday. It was the sole drive connected to the system as ID0, booting from floppy. The system hung at the point in the DOS initialization (with the 73GB drive's access LED stuck on) where it reads the partition table of the hard disk(s) before …

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Re: Why did NES games generally look less pixelated/lo-fi than CGA/EGA PC games?

Posted on 2023-09-24, 19:30

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by mkarcher

in Milliways

in Milliways

Another reason may be the color palette. Especially the 4-color CGA palette(s) do not allow anything close to smooth color transition, so every color change is a sharp high-contrast edge. The NES allowed to choose from 55 colors . In 200-line mode, even EGA allowed only the 16 RGBI colors, which is …

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Re: Showing some love for Adaptec's ugly ducklings: Adding big drive support to EISA and VL controllers

Posted on 2023-09-24, 18:03

by

by mkarcher

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Perhaps that is only a display bug in this particular case, but it seems like too much of a coincidence. I'm guessing there is a similar truncation elsewhere in the code I made an updated BIOS (patch not yet upload to GitHub) that fixes the ID0 bug. It fixed the issue in the 9GB / 36GB combination: …

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