[Coco] Hard drive modes.

[L. Curtis Boyle]

LBA means seeks are done by just sector number (newer style). CHS means you have to specify Cylinder, Head, and Sector numbers. Since OS-9 uses cluster/sector numbers, LBA can map directly (well divide by 2 since most drives are 512 byte sectors, but that’s just a shift right). With CHS, you have to do math, which takes more code/cycles.

L. Curtis Boyle
curtisboyle at sasktel.net



> On Dec 31, 2014, at 1:57 PM, Allen Huffman <alsplace at pobox.com> wrote:
> 
>> On Dec 31, 2014, at 11:51 AM, L. Curtis Boyle <curtisboyle at sasktel.net> wrote:
>> 
>> I did fill up a 128 MB drive, but that was because I was keeping a lot of sound and graphics files that weren’t specifically Coco related. The IDE driver I did for Glenside did support LBA and CHS modes, but LBA is a lot easier (and less code required) to support. 
> 
> I am going to stop pretending I remember what LBA implies. Could you refresh me/us? I do not know if I am familiar with CHS at all.
> 
> My personal CoCo hard drives have been: Burke & Burke MFM/RLL (OS-9), KenTon SCSI (RGB-DOS), and SuperIDE (OS-9/HDB-DOS). I expect I have forgotten everything I am going to need to know to get the CoCoSDC acting like an OS-9 hard drive...
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