There are some operating systems like DOS that do not have access to cylinders over 1023.
So I'd recommend to use LBA or AUTO for maximum compatiblity.

So LBA is only used for lowering the Cylinder count?

Whats the max side if hdd that still can use that LBA setting trick (limited to 1024 cylinders)

Depending on your BIOS you may face a limit at 32 GB or 64 GB.
BIOS may hang at startup then.
At 128 / 137 GB its size may be capped, if your BIOS does not have 48-bit LBA support.

All modern HDDs use LBA.
This on your screenshot is just the CHS translation for legacy systems like DOS.

LBA is a type of "translation" of CHS. If you set 1023c x 255h x 63s x 512k/sector = 8,414,461,440 or 8.41G (or as reported by DOS ~ 8.2G)

Disruptor wrote on 2023-01-21, 17:46:

Depending on your BIOS you may face a limit at 32 GB or 64 GB. BIOS may hang at startup then. At 128 / 137 GB its size may be ca […]
Show full quote

Depending on your BIOS you may face a limit at 32 GB or 64 GB.
BIOS may hang at startup then.
At 128 / 137 GB its size may be capped, if your BIOS does not have 48-bit LBA support.

All modern HDDs use LBA.
This on your screenshot is just the CHS translation for legacy systems like DOS.

Motherboard bios doesnt go over 8,4 GB..

Only with the MR bios rom i could do over 64GB.. But havent tested it out yet.

Windows 95 can just use the normal or large setting..

When will the large setting be valid?

My experience would be that if you set normal, DOS will only see ~500ish MB, if you set large it will only see ~2000ish MB (It was an intermediate standard until full LBA, for using disks up to 2G AFAICR) so you want to set it to the recommended LBA to use most of the disk, in partitions as large as the OS in use will allow, but in this case might be a small handful of MB short.

Robin4 wrote on 2023-01-21, 18:10:

Disruptor wrote on 2023-01-21, 17:46:

Depending on your BIOS you may face a limit at 32 GB or 64 GB. BIOS may hang at startup then. At 128 / 137 GB its size may be ca […]
Show full quote

Depending on your BIOS you may face a limit at 32 GB or 64 GB.
BIOS may hang at startup then.
At 128 / 137 GB its size may be capped, if your BIOS does not have 48-bit LBA support.

All modern HDDs use LBA.
This on your screenshot is just the CHS translation for legacy systems like DOS.

Motherboard bios doesnt go over 8,4 GB..

Only with the MR bios rom i could do over 64GB.. But havent tested it out yet.

That was a general rule.
And it seems your BIOS will go over 8 GB.

Normal means CHS access (int13) is passed through to the disk, with the 504 MB limit for IDE disks due to the famous lowest maximum C/H/S definitions in IDE and int13

Large means CHS access goes through some arbitrary kind of conversion usually but not necessarily based on bit shifts goes on, this has various implementations (and so is not guaranteed compatible across PCs or, for that matter, int13 implementations such as if you switched to the XTIDE option rom), some break at around 2 GB, some can go all the way to 8 but are less compatible because of MS's 256 heads bug (there may be a "Large disk access mode = DOS or Other" option to limit them to 255 wasting some capacity, or a functional equivalent to this option may be always on)

LBA means CHS access is converted to a sector number and LBA(28) mode is used instead, this is generally the best option - if your disk supports LBA that is!

Of course, all of these stop at the int13 maximum of 1024/256/63 and none of this applies to "int13x", which is proper LBA passthrough...

...So, what's up with that Normal numbers if I said int13 is limited to 1024/256/63?
Well, something does really apply even to true LBA mode - the BIOS still needs to know the hardware-compatible CHS capacity for the "extended disk parameter table", but then who knows what it will declare in int13 for capacity - maybe 504MB (1024/16/63), maybe something invalid, who knows? 😁
(I keep a few disk detection utilities on my main DOS floppy to try to investigate...)

I have a 2011 computer, apparently designed in 2009, that works reasonably with most HDDs which only declare 1024/256/63 as their CHS capacity, but is broken for MS operating systems with CF cards that are designed to support CHS up to 127 GB!

Robin4 wrote on 2023-01-21, 18:10:

Only with the MR bios rom i could do over 64GB.. But havent tested it out yet.

Impossible - or rather, guaranteed not to allow int13 access over the 8 GB limit; might still be valuable if the original firmware has a lower maximum for LBA/Large or outright freezes with an oversize disk!

BitWrangler wrote on 2023-01-21, 18:19:

My experience would be that if you set normal, DOS will only see ~500ish MB, if you set large it will only see ~2000ish MB (It was an intermediate standard until full LBA, for using disks up to 2G AFAICR) so you want to set it to the recommended LBA to use most of the disk, in partitions as large as the OS in use will allow, but in this case might be a small handful of MB short.

Very helpfull information there.. Thank you.

Didnt thought about that.

Hi Robin4

If you want to read up on the theory behind these BIOS limits, I wrote a "The BIOS IDE Harddisk Limitations" article back in 1999. It is still available at: http://www.steunebrink.info/bioslim.htm

You will need a BIOS from 1998 or later to find the Int 13h extensions nessary to break the 8GB limit. The latest AB-PT5 BIOS on TRW is from 04/18/96, so I'm sure this BIOS is limited to 8GiB.

Jan

Edit: updated my website link

Already find out that the AB-PT5 wont getting any further then 8GiB.. Because i tried a 20GiB disk on the onboard controller.. And it only showed about 8455 Mb of that disk.

Also still playing with bios roms, and see what is the best alternative for me to get the most out of the hardware.

But nice to know from you that i need at least a bios from 1998 or later to break that 8GB limit. (its not easy if i want to build a classic pentium 90 system, it want to use almost period correct motherboard) But i will see what i can get out of it.
But i think an add on controller would be the only solution to solve the onboard controller issue.. Or going with a lower capacity there if thats the better way (or use a low capacity drive only as OS boot drive)

Also remember that BIOS limits don't translate into Windows drive size limits as Windows doesn't use BIOS for hard drive access. It may be possible to fully format and partition a hard drive on another machine, prepare a lower partition that is within BIOS limits and a separate higher partition above that. Windows then would be installed into the lower partition. As long as you are able to configure the hard drive in BIOS in a way to make it boot and access the whole lower partition you should be fine in Windows. In DOS only the lower partition would be visible.

An alternative more robust solution is a PCI ATA 66/100 controller. You would disable the built-in one in BIOS. Boot sequence configuration in BIOS still has an effect. This way you can install a 127GB hard drive into a 486. So old BIOS limits are not such a big issue.

yes iam already playing with those PC ATA 33 / 66 controllers with bios.. But iam also thinking to install a ISA NIC card in the system and add a Eprom or eeprom with the DTC 32 GB LBA bios rom on it.
Iam only curious to see how it will work in the end.. I dont have the right eprom / eeprom for doing that at the moment.. And have to order 1 or 2 first, before i can go on.

What to choose from to install the DTC 32GB rom on the NIC.. Which one would be have a longer life span? Eprom or eeprom or a flash chip?

For my other not so great working FIC- PA2000 motherboard thinking of replacing the old style 32 DIP package to a 32 pin PLCC package.
DIPs are harder to get these days, and PLCC are cheaper to get.. Should be the same device at the end.