Welcome, Guest. Please login or register.

Author Topic: compact flash question  (Read 2507 times)

Description:

0 Members and 1 Guest are viewing this topic.

Offline Thomas

Re: compact flash question
« on: April 05, 2013, 08:36:58 AM »
For CF cards the same limits apply as for hard disks. 4 GB is an OS limit. You need to install updated drivers to use larger drives. The boot partition always has to be inside the first 4GB. Sizes up to 2 TB are possible with the right drivers and a matching file system.

Up to 8 GB is possible with a new file system only (no driver patches needed and no limit for the boot partition). For example these:
http://aminet.net/package/disk/misc/ffstd64
http://aminet.net/package/disk/misc/PFS3_53

(Some CF cards report CHS values which are higher than allowed by the specs. With these special cards even more than 8GB is possible.)
« Last Edit: April 05, 2013, 08:43:28 AM by Thomas »
 

Offline Thomas

Re: compact flash question
« Reply #1 on: April 05, 2013, 03:32:41 PM »
Quote from: paul1981;731362
I would just like to add that make sure you do indeed create two partitions if you're using a CF/HDD larger than 8GB (unless you have a custom kickstart ROM chip with latest scsi.device). And of course, use PFS3 or SFS.


Yes, that's true generally. But as mentioned above, there are a few (probably cheap) CF cards which report their real size through CHS although this is not allowed by the ATA specs. With these CF cards you can have one large partition as long as the file system supports Direct-SCSI (which rules out SFS but qualifies FFS V44).

Offline Thomas

Re: compact flash question
« Reply #2 on: April 06, 2013, 07:54:36 AM »
Quote from: paul1981;731389
If a user has one single bootable partition of capacity greater than 8GB, and he or she has standard 2/3/3.1 roms, then if the Startup-sequence is edited when the disk data is beyond the 8GB barrier (standard old scsi.device limit) then the Startup-sequence will be rendered unreadable by the system. :nervous:



Why should this be? Don't you read what I write? If you use a file system which uses direct-scsi commands, you can use all capacity the scsi.device recognises as one partition. If you don't have such a file system, all partitions (not only the boot partition) are limited to the first 4 GB of the drive. File corruption only happens in the latter case, if you don't limit partitions to the first 4GB of the drive.

File systems with direct-scsi capability include the old SFS V1.84, FFS V44 (which is the result of the FFSTD64 patch), PFS3 DS and PFS3 AIO.

There is no 8GB limit as such, but scsi.device limits the capacity to what the drive reports. I the drive reports its size according to the ATA specs, the capacity is limited to 8GB. But if the drive does not follow the ATA specs and reports its real size, scsi.device can use all the capacity with direct-scsi commands.

Only if you want to patch scsi.device and then use a file system which does not use direct-scsi but TD64 or NSD, then you need to arrange the boot partition inside the first 4GB and can have other partitions outside.

Another problem can arise if you use FFS (V43 or higher) with big partitions but don't have enough RAM to allow the disk-validator to validate the partitions. Then the affected partition will remain full and write protected although there are no files on it.

Offline Thomas

Re: compact flash question
« Reply #3 on: April 06, 2013, 04:28:50 PM »
The next limit above 4GB is 2TB. The limits shown above only apply to the internal IDE controller of the A1200/A600/A4000. (The IDE driver is called scsi.device for compatibility, other than that there was no mentioning of SCSI yet. Direct-SCSI is a software interface. The IDE driver also interpretes these commands, it's not necessary to have SCSI hardware for this.)

But there are also file system limits. PFS3 has a limit of 100 GB, SFS has a limit of 128 GB for a partition.

Offline Thomas

Re: compact flash question
« Reply #4 on: April 07, 2013, 10:12:21 PM »
All you say is true for all drives but a few. Those few drives do illegal things with the response to a capacity query and thus allow scsi.device to access the entire drive and not just the first 8 GB as it should be.

There is the explanation: http://eab.abime.net/showthread.php?p=846925#post846925

So a lucky guy might be able to use a 32 GB CF card with just a Direct-SCSI file system and no scsi.device patch. Bad luck for you that you never saw such a drive.