Timeline for Origin of CHS geometry limits in BIOS calls
Current License: CC BY-SA 4.0
11 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Oct 21 at 15:56 | comment | added | Justme | @Netch actually, these answers might not answer your question - I simply stated the Xebec controller used this notation for writing CHS data, but why the notation is like that is still unknown. The Xebec controller has it's own Z80 CPU which made it an easily adaptable hard drive interface for any machine, so the protocol between BIOS and the Z80 code could have been anything. Maybe it existed in same form already in some other machine and it fit the BIOS interface without modifications, maybe IBM engineers asked Xebec how to best adapt their current BIOS API, who knows. | |
| Oct 21 at 11:50 | comment | added | Netch | Thanks, assumed true (with additions from a neighbor answer). | |
| Oct 21 at 10:16 | history | edited | Justme | CC BY-SA 4.0 |
added 107 characters in body
|
| Oct 21 at 9:28 | history | edited | Justme | CC BY-SA 4.0 |
added 360 characters in body
|
| Oct 21 at 9:19 | comment | added | Justme | @Netch Sort of. I mean they use Xebec chipset as hard drive controller, and the Xebec chipset wants the sector and cylinder data in that specific two byte format, and hard drive BIOS then uses that same two-byte format to avoid conversion/repacking of the values. Less moving data around that way, more moving data around if done in other way. | |
| Oct 21 at 9:04 | comment | added | Netch | So do you mean this was from hardware designers which selected the simplest way they saw, but BIOS guys avoided then to repack the values? | |
| Oct 21 at 9:02 | history | edited | Justme | CC BY-SA 4.0 |
added 196 characters in body
|
| Oct 21 at 9:00 | comment | added | Justme | @Netch The XT hard drive controller wants the sector and cylinder bytes to be written in that format. I will add that to the answer. | |
| Oct 21 at 8:49 | history | edited | Justme | CC BY-SA 4.0 |
added 242 characters in body
|
| Oct 21 at 8:46 | comment | added | Netch | Well, the important thing in your answer is that ATA geometry came later than XT. I missed this initially. But all this doesnʼt answer why XT developers stole bits from the sector number, which was much more plausible to grow, than from the head number. | |
| Oct 21 at 8:43 | history | answered | Justme | CC BY-SA 4.0 |