MaxTransfer for IDE-CF

[lurkist]

Got my Compact Flash card up and booting in a spare A1200 after a mishap with (literally) crossed wires!  Works a charm, but I only have a 32MB card for now, waiting for a cheap large one on eBay.

Question -

Since CF cards generally seem to claim 8MB per second, what Max transfer settings are people using?

Cheers

[Thomas]

MaxTransfer has nothing to do with speed. Set it to 64k and your are fine in all situations.

You won't get more than 2MB per second with the internal IDE bus anyway.

Bye,
Thomas

[lurkist]

64k - doesn't sound like something I'd type into that field, eg. default is

0xffffff

but is apparently best suited to SCSI drives.

I've seen an example for IDE drives that says

0x1fe00 or
0xfe00

I also found this on a FAQ -

"For unknown drives, the maximum "safe" value is 0x0001FE00. Other (older) drives may require 0x0000FFFF or even 0x0000FE00. The sure test is to copy files larger than the MaxTransfer value to and from the drive, checking for corruption afterwards. Pictures work well for this, as corruption is easy to detect."

but what does it all mean?!?

I'm assuming they're HEX values which I don't understand.  Is there a calc util to decipher these strange figures?

Cheers

[lurkist]

OK, according to a HEX calc util I found on Aminet, the figures above mean-

0xffffff = 16777215
0x1fe00  = 130560
0xfe00   = 65024

There seems to be no logic behind them, particularly the default which is wayyy bigger than the reccomendations.

64k = 0xfa00  Should I type this in?

[KThunder]

max transfer is an old setting that is hardley used anymore. old drives would corrupt large files if the setting was too large. newer drives shouldnt have a problem no matter what setting you put.
this is something that resurfaces regularly by people who apparently think it is a problem. do a google search for ifaq or irritatingly fequently asked questions and see what they say about it. they tell you to try every concievable setting and tell them if it makes any difference.
it doesnt (no i didnt try i have ide and scsi tech manuals and protocal docs for drives from 8bit ide scsi to udma 166 eide and ultrawide scsi) cf drives use new protocals while most amiga interfaces use generic settings. safe but slow

[Thomas]

@lurkist:

64k = 64 * 1024 = 65536 = 0x10000

0xfe00 is fine, too, it's one block (512 bytes) less than 64k.

@KThunder:

It's rather so that new drives corrupt files with larger values because manufacturers don't test their drives with large values. At least that's what I heared.

There are more problems with larger MaxTransfer values than with low ones and there are new posts about MaxTransfer problems every now and then in different forums. So you cannot say that MaxTransfer is an old setting which does not affect current drives.

Bye,
Thomas

[mrmkl]

I think that setting Maxtransfer low enough makes the IDE device drivers ask not more than a certain amount of sectors to read or write per one IDE (or ATA) command. So the problem could come because of buggy firmware on the IDE disk, which doesn't do the correct amount of data transfer when it gets certain values to the sector count register. For example, the value "0" to this register should ask for 256 sectors in (certain, if not all, revisions of) the ATA-standard, but if then the IDE drives behaves wrong, data could get corrupted on the disk?

[Thomas]

Exactly.