[Coco] Super IDE vs. Drive Pak

[John Kent]

For some reason I thought CF cards were limited to 2GB.
I can't remember why I thought that.
If you look at the IDE register interface you'll see you should be able 
to address up to 137GB.
For 160GB drives and beyond, I'm not sure what happens.
There must be some additional registers or bits somewhere.

A2 A1 A0 D15-D8   D7-D0
0  0  0  Odd Data Even Data
0  0  1           Error / Feature
0  1  0           Sector Count
0  1  1           Sector Number    LBA  7- 0 (                  256 * 
512 =         131,072)
1  0  0           Cylinder Low     LBA 15- 8 (            256 * 256 * 
512 =      33,554,432)
1  0  1           Cylinder High    LBA 23-16 (      256 * 256 * 256 * 
512 =   8,589,934,592)
1  1  0           Select Card/Head LBA 27-24 ( 16 * 256 * 256 * 256 * 
512 = 137,438,953,472) * 2 Drives
1  1  1           Command/Status

C/D/H = 1, LBA, 1, Drive, Head (LBA 27-24)

137.5GB * 16 = 2.2TB but then you lose the LBA and Drive bits
(from the Apacer Compact Flash AP-CFXXX22 specification sheet)
It assumes 512 byte sectors. I believe 2TB hard disks and beyond use 
4096 byte sectors which are only readable by Windows 7 and beyond and 
not windows XP so perhaps you can squeeze another factor of 8 out of the 
IDE register set.

John

On 16/11/2011 11:34 PM, Mark Marlette wrote:
> All,
>
> Good thread!
>
> Input has been gathered and we will be making some changes at Cloud-9 on the SuperIDE product based upon this great feedback. More to follow on that.
>
> Just want to clear this misconception. The SuperIDE DOES NOT have a size limit other than the CF spec itself. If you want to plug a 64GB CF, do so. The limitations are placed upon it are by NitrOS-9 and or HDB-DOS. This is a 24bit LSN, which is a bit over 4GB, IIRC. So is it practical to have a 4, 8, 16, 32,64GB CF on the CoCo? No, but if you want to you can.
>
> I ship with a 256MB just because it is a sweet size. 84MB partition for HDB-DOS and a 127MB partition for NitrOS-9, with another small partition with the remainder available. The reason for this is that there as several utilities under OS-9 that ASSUME a cluster size of one! Run those on a non 1 cluster size and POOF-BAM goes the drives structure. IMHO, not worth it. B&B are the biggest offender. Who would have thought we would be here today doing what we are doing? All GREAT tools, thus my basis of my partition sizes.
>
> How many people have more than 127MB of data/programs on their NitrOS-9 drive? Sure there are some. For those who want to have a 4GB partition, then you can do that on what ever size CF GREATER than that you select. Fill the 4GB partition up?? Not likely.
>
> Options are good. :)
>
> Any case, thank you all for the support and the great feedback. You will like the results. :)
>
> Regards,
>
> Mark
> Cloud-9
> http://www.cloud9tech.com
>
>

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