VOGONS


First post, by XboXC

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I have mb468 motherboard (i486) and ibm 4.3GB hdd. But bios detect it as 107MB. And i cant boot from hdd. When i boot from floppy and check „dir” command on C: i get normal size of partition (~2GB for fat16).

Main "PC":
----------
Mac Pro Xeon 2x 3GHz (Quad), 12GB RAM, MacOS 10.15, Radeon HD 5770

Retro:
-----
Apple Macintosh Quadra 650, 68040 33MHz, 64MB RAM, Mac OS 8.1
PC (clone): Intel 80486 DX2 66MHz, 64MB RAM, Windows 3.11 WfW, ATI Rage2

Reply 1 of 12, by douglar

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Is this your motherboard? https://theretroweb.com/motherboards/s/powertech-mb468#bios

What BIOS do you have? BIOS dated before June 1994 often have trouble with drives > 512MB. Try upgrading to the latest BIOS if you don't have the latest. It has a December 1994 date, which means there's a pretty good chance that it can handle drives between 512MB and 8GB correctly.

If you already have the latest BIOS, consider adding XT Ide Universal Bios as an option ROM. https://xtideuniversalbios.org/

If you are not interested or able to write a new eeprom, try using a drive overlay like ez drive.

http://vogonsdrivers.com/getfile.php?fileid=1900

Last edited by douglar on 2025-01-16, 13:13. Edited 1 time in total.

Reply 2 of 12, by XboXC

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The bios that i have is from 1995. Is newer. That bios have LBA mode (and normal and large). I have second hdd 1.2GB and it works properly

Main "PC":
----------
Mac Pro Xeon 2x 3GHz (Quad), 12GB RAM, MacOS 10.15, Radeon HD 5770

Retro:
-----
Apple Macintosh Quadra 650, 68040 33MHz, 64MB RAM, Mac OS 8.1
PC (clone): Intel 80486 DX2 66MHz, 64MB RAM, Windows 3.11 WfW, ATI Rage2

Reply 3 of 12, by douglar

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XboXC wrote on 2025-01-16, 13:13:

The bios that i have is from 1995. Is newer. That bios have LBA mode (and normal and large). I have second hdd 1.2GB and it works properly

Well, can you configure the drive to use the correct CHS values or LBA values in your BIOS?

Reply 4 of 12, by XboXC

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Only in „normal” mode. But i dont try that

Main "PC":
----------
Mac Pro Xeon 2x 3GHz (Quad), 12GB RAM, MacOS 10.15, Radeon HD 5770

Retro:
-----
Apple Macintosh Quadra 650, 68040 33MHz, 64MB RAM, Mac OS 8.1
PC (clone): Intel 80486 DX2 66MHz, 64MB RAM, Windows 3.11 WfW, ATI Rage2

Reply 6 of 12, by Chkcpu

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Hi XboXC,

This MB468 board has an Award BIOS and as douglar pointed out, all these BIOSes from July 1994 or later correctly support IDE drives up to 8GB.

However, Award BIOSes from 1994 and 1995 have a small bug. This so called “2GB Harddisk size display limit bug” limits the harddisk size display, on the BIOS Setup and boot screens, to 2015 MiB / 2113MB. Whenever a drive is 2016 MiB/2114MB or larger, the display starts to count from zero again. The same happens at 4032/4228 and 6048MiB/6342MB.
This looks a lot like a 2 GB BIOS limit but is actually only a bug in the calculation of the harddisk size for display, and it doesn't affect the BIOS support for these large drives.

So your 4.3GB should work normal with this board and the BIOS is telling you that it detected an 107+4228=4335MB drive.
So just use the HDD Auto detect, select/check LBA mode and disregard the incorrect size display. When using Fdisk after that, you should see the full 4134MB drive size.

That being said, there is a fix for this bug. You can read about it at Re: Diy modding support for k6+And 120gb hard drives into bios roms
If you want this fix, do you have an (E)EPROM programmer to read your present BIOS and write a new EPROM after the fix?

Cheers, Jan

CPU Identification utility
The Unofficial K6-2+ / K6-III+ page

Reply 7 of 12, by douglar

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Chkcpu wrote on 2025-01-17, 15:31:

However, Award BIOSes from 1994 and 1995 have a small bug. This so called “2GB Harddisk size display limit bug” limits the harddisk size display, on the BIOS Setup and boot screens, to 2015 MiB / 2113MB. Whenever a drive is 2016 MiB/2114MB or larger, the display starts to count from zero again. The same happens at 4032/4228 and 6048MiB/6342MB.
This looks a lot like a 2 GB BIOS limit but is actually only a bug in the calculation of the harddisk size for display, and it doesn't affect the BIOS support for these large drives.

Thanks for the info. I added it to the storage Wiki

https://www.vogonswiki.com/index.php/Storage# … age_Limitations

Reply 9 of 12, by XboXC

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Chkcpu wrote on 2025-01-17, 15:31:
Hi XboXC, […]
Show full quote

Hi XboXC,

This MB468 board has an Award BIOS and as douglar pointed out, all these BIOSes from July 1994 or later correctly support IDE drives up to 8GB.

However, Award BIOSes from 1994 and 1995 have a small bug. This so called “2GB Harddisk size display limit bug” limits the harddisk size display, on the BIOS Setup and boot screens, to 2015 MiB / 2113MB. Whenever a drive is 2016 MiB/2114MB or larger, the display starts to count from zero again. The same happens at 4032/4228 and 6048MiB/6342MB.
This looks a lot like a 2 GB BIOS limit but is actually only a bug in the calculation of the harddisk size for display, and it doesn't affect the BIOS support for these large drives.

So your 4.3GB should work normal with this board and the BIOS is telling you that it detected an 107+4228=4335MB drive.
So just use the HDD Auto detect, select/check LBA mode and disregard the incorrect size display. When using Fdisk after that, you should see the full 4134MB drive size.

That being said, there is a fix for this bug. You can read about it at Re: Diy modding support for k6+And 120gb hard drives into bios roms
If you want this fix, do you have an (E)EPROM programmer to read your present BIOS and write a new EPROM after the fix?

Cheers, Jan

Yes dos and win3.11 see good size (4.3) but i cant boot that from this disk. After bios post screen i see black/white table with pc parameters and only blinking cursor. Theres no text „error boot” or „no booting disk” or similar - just cursor. That is main problem. How can i fix it?

Main "PC":
----------
Mac Pro Xeon 2x 3GHz (Quad), 12GB RAM, MacOS 10.15, Radeon HD 5770

Retro:
-----
Apple Macintosh Quadra 650, 68040 33MHz, 64MB RAM, Mac OS 8.1
PC (clone): Intel 80486 DX2 66MHz, 64MB RAM, Windows 3.11 WfW, ATI Rage2

Reply 10 of 12, by jmarsh

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Probably doesn't have a proper boot sector, try running "fdisk /mbr" to write a new one.

Reply 11 of 12, by XboXC

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Yes i think when bios calculate wrong size, they dont see properly boot sector.

Main "PC":
----------
Mac Pro Xeon 2x 3GHz (Quad), 12GB RAM, MacOS 10.15, Radeon HD 5770

Retro:
-----
Apple Macintosh Quadra 650, 68040 33MHz, 64MB RAM, Mac OS 8.1
PC (clone): Intel 80486 DX2 66MHz, 64MB RAM, Windows 3.11 WfW, ATI Rage2

Reply 12 of 12, by XboXC

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You right. I just use fdisk /mbr and thats it. Its working. Thanks 😁😁😁

Main "PC":
----------
Mac Pro Xeon 2x 3GHz (Quad), 12GB RAM, MacOS 10.15, Radeon HD 5770

Retro:
-----
Apple Macintosh Quadra 650, 68040 33MHz, 64MB RAM, Mac OS 8.1
PC (clone): Intel 80486 DX2 66MHz, 64MB RAM, Windows 3.11 WfW, ATI Rage2