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Disk Boot Faulure on good hardware

NeXT

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So this machine I built will not boot form floppy. IT will boot from IDE if it wants to but first I need to floppy boot it to install DOS. ;)

Same as the DOM boot thread, ASUS ISA-486SV2 Rev. 3.1 and ISA combination floppy/IDE controller with the GoldStar PRIME 2 chipset. Both support 720k and 1.44mb floppy formats. Motherboard has a good battery and default CMOS configuration. Have tried two different floppy cables, have tried three other 3.5" floppy drives and I have both a 720K and 1.44mb floppy I have formatted and sys'd on another machine and verified they are bootable. This machine will not boot. It just says DISK BOOT FAILURE as soon as it tries to read from the floppy. That I can tell it's not corrupting or physically damaging the disks. I've also tried a different controller card with the same result. Have also tried with TURBO both turned on and off.
There's three cards in this machine. The Disk I/O card, the VLB video card and a tape drive controller (which I've removed for testing with no change)

Edited: As a test of my sanity I recabled the floppy drives and tried booting from a known good 360k 5.25" floppy. No change. I also rejumpered the motherboard as I had originally received and and swapped back in the 40mhz DX-40 I received it with. Still no go.
 
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kc8eyt

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Man I hate issues like yours. This is when I start trying the things that in my mind couldn't possibly be the issue. Looking at the setup you described I would try a standard ISA video card next. I know, VLB shouldn't cause any issues, but like I said, time to try anything. :) I would then try playing the binary shuffle by moving the I/O and video cards to different combinations of slots.

I just refurbished a Micron Pentium 133 system that I installed a 3D Virge 4MB video card into. The video card will *only* fire up in PCI slot #1. Why? Don't know. But it wasn't until I started playing the binary shuffle that I figured that out. The other PCI slots work fine with different cards (NIC, Sound, Etc..) Just weird.
 

Agent Orange

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So this machine I built will not boot form floppy. IT will boot from IDE if it wants to but first I need to floppy boot it to install DOS. ;)

Same as the DOM boot thread, ASUS ISA-486SV2 Rev. 3.1 and ISA combination floppy/IDE controller with the GoldStar PRIME 2 chipset. Both support 720k and 1.44mb floppy formats. Motherboard has a good battery and default CMOS configuration. Have tried two different floppy cables, have tried three other 3.5" floppy drives and I have both a 720K and 1.44mb floppy I have formatted and sys'd on another machine and verified they are bootable. This machine will not boot. It just says DISK BOOT FAILURE as soon as it tries to read from the floppy. That I can tell it's not corrupting or physically damaging the disks. I've also tried a different controller card with the same result. Have also tried with TURBO both turned on and off.
There's three cards in this machine. The Disk I/O card, the VLB video card and a tape drive controller (which I've removed for testing with no change)

Edited: As a test of my sanity I recabled the floppy drives and tried booting from a known good 360k 5.25" floppy. No change. I also rejumpered the motherboard as I had originally received and and swapped back in the 40mhz DX-40 I received it with. Still no go.
From my experience with 486's of that ilk, I would double check the BIOS settings and make sure the onboard floppy controller is disabled. Other than that maybe swap out the RAM. I know, not much wisdom here but worth mentioning.
 
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mR_Slug

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Have you tried a different FDD controller? had as PS/2 Model 65sx that with a known good disk, FDD and cable, refused to boot. AFAIK the FDD controller is bad. Also check boot sector virus. BTW your youtube is great.
 

NeXT

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I'm on my fifth controller, in fact. At this point it is VERY unlikely to be a bad controller, cable, drive or floppy.

So I switched out the VLB video card for a more generic ISA Trident to no avail, then I replaced the ram with 4mb that I know were tested and switched off the internal and external cache with no success. Time for the nuclear option.

IMG_8348.JPG


Different motherboard, same CPU, ram, VLB video card, power supply and the original controller card and it booted the floppy as soon as I had the drive configured. It has to be the motherboard. :?
There is three revisions of this board. The 2.4, the 2.5 and the 3.1 that I have and guess which one I cannot find the jumper charts for? (and yes things changed between revisions). This board has no onboard I/O or disk controllers and its your regular AMI BIOS.

Edited: sorry, the jumper designations for the 3.1 exist but they're really confusing. Since the system presumably was configured as-is when I got it it should already work fine so I'm stumped.
 
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NeXT

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Okay here's a hot take.

So I used this other motherboard to format and install MS-DOS on an IDE DOM, then I swapped that out for the Asus board and booted up using the C: drive.
MS-DOS reports a Data Error when you try to access either floppy drive but otherwise the system seems to be running fine, so whatever is causing the floppy system specifically to malfunction is not otherwise interfering with the rest of the computer or MS-DOS, but at least now we have a way to load any diagnostic programs anyone can think of that might better answer what is going on.
 

modem7

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I noted a past thread on these forums.
My recorded summary is, "Thread 42994: Acer VI15G motherboard. SETUP option 'video cacheable option' preventing boot from floppy."
An example of how odd the relationship between symptom and cause can be.

(BTW. The recent migration of vBulletin appears to have renumbered the old threads.)
 

NeXT

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Nope, disabling video BIOS shadow/caching doesn't fix it either. As a shot in the dark I also went through the DOS Benchmark Pack to see if I could make it choke on something like bad cache, a bad CPU or ANYTHING really. All I could determine is that the BIOS has the Y2K bug (but I set it to 1994 so that didn't matter here) and I underestimated the performance of this VLB Trident card. :)
 

NeXT

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Someone over on VOGONS suggested I verify that we have working DMA by testing to see if both serial ports work. They do.
The floppy controller needs DMA 2 in order to use the floppy drive. Sure enough I pulled out the other POST card and I can see IRQ6 when the floppy drive is polled but no DMA.

IMG_8368.JPG


I beeped out and verified that DRQ2 and DACK2 was present on each ISA slot and that looked okay. DACK2 connects to U24 pin 13 (74LS138N) which goes to the chipset while DRQ2 goes to U8 pin 13 (74F151BN) and I could beep all the pins back to the chipset, except for Z̅. It seems to connect to a trace layered in the board but was not connected to the chipset directly. I have no idea if that could be the fault or if it's not important in this case.


Edited: Oops, the POST card was not fully seated in the board. We do actually have DMA2.

IMG_8370.JPG
 
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Ruud

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Someone over on VOGONS suggested I verify that we have working DMA by testing to see if both serial ports work.
I beg your pardon but IMHO the serial ports don't use DMA. It is another matter using LPT ports in ECP mode. But to be honest, I have no idea to test that.

Having read all, my idea is that the FDC chip is broken. If the FDC is part of a bigger IC, then you can have a problem: replacing these ICs is a problem. And you have to find a replacement in the first place.

FYI: I have 8086 board that has a broken internal FDC so I know that it is possible.
 

NeXT

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Having read all, my idea is that the FDC chip is broken. If the FDC is part of a bigger IC, then you can have a problem: replacing these ICs is a problem. And you have to find a replacement in the first place.

Did you at all see the above post where I booted with no issues using a different motherboard but the same floppy drive, cable AND disk controller, then proceeded to see the fault persist on several other controllers?
 

Timo W.

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There are two settings to check in the BIOS:

1. Cache mode. If it is set to write-back, change it to write-through. A non-working floppy is one of the side effects when something is not compatible with WB mode (often with AMD CPUs)

2. Virus protection. Some Bioses of that time had a built-in virus protection that did strange things when accessing the mbr/boot sector. Disable that.
 

NeXT

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It was something way more insane.
One of the three SN74F151's that handle DMA multiplexing for the chipset had a broken pin. The floppy controllers could all request DMA channel 2 but it would never reach the chipset. I desoldered it after suspecting it might be bad and swapped it with a neighboring chip, predicting the floppy would come back and the IDE channel would fail. Sure enough, it did.

CGS_10577.JPG

CGS_10576.JPG


I soldered a new leg onto the chip and it seems to be all good now.
 

kc8eyt

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How the shiznit did that happen?

Awesome troubleshooting by the way.
 
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