alt Hacker NewsThanks for trying to educate the young whippersnappers about hard drives, but a lot of this rambling seems entirely off-topic.
>Unless you can manually set CHS in BIOS to match, which a USB adapter won't let you do anything you want like BIOS. A Pi could substitute for that but it was never really a good idea, mainly useful to set a non-default CHS on one drive to match the default CHS on an established drive when both are plugged into the same motherboard.
USB hard drives act as SCSI block devices, they don't have a CHS geometry and sectors are addressed by a single number (LBA=Linear Block Address).
Again: the purpose of this device is to connect an OLD HARD DISK to a MODERN COMPUTER. Not the other way around! If you plug it in and try to boot from with a BIOS / UEFI CSM that supports this, it will make up a CHS geometry based on the total number of sectors, instead of using the (real or translated) one that the drive actually uses and reports in its "IDENTIFY DEVICE" response. Because it's connected over USB and behaves like any other USB mass storage device.
That may well lead to problems when booting DOS from a drive that was formatted in some other machine, because the MBR will not use the same geometry. But that's not what this is for.
>If I was being very skeptical, I would say it's possible the coder didn't even know that USB adapters exist.
From the second paragraph in the readme: «« While cheap, modern adapters usually only work with newer "LBA" type drives, ATAboy works all the way back to the earliest CHS only, PIO Mode 0, ATA disks. »»
Good to get your message. Upvote for sure.
There were a lot of "non-standard" elements to work around through time, since there wasn't actually a real standard. More info can always help from many viewpoints and experiences and still not cover it all, young or old the more that have something to give as well as something to learn is a winning combination :)
The CHS values are still present in the partition table along with LBA equivalent, SCSI or not. Only with MBR layout though, not GPT. Some systems have never paid attention to CHS, some have never stopped. Like different forms of DOS.
Which is why a proper USB adapter is intended to just work with a PIO-0 HDD, and usually does unless the data layout on the old drive is so uncommon to be the kind of edge case that would be a show-stopper when connected to a vintage ATA motherboard too. That would require the unique CHS to be manually set in the BIOS to conform to a "custom" layout that was so non-mainstream for some reason when the old HDD was set up.
Then you had "drive overlays" which can get even more challenging when you're connecting old HDDs to newer PCs so often it makes you blue in the face :)