Subject: Re: Maxtransfer
From: [email-masked] (microbotics1 on BIX)
Date: 31 Jan 94 19:00:23 GMT
Newsgroups: comp.sys.amiga.hardware

[email-masked] (Marek Tomczyk) writes:

>In article <[email-masked]>,
>Lionel Tun <[email-masked]> wrote:
>>What is maxtransfer and to what should it be set for a 
>>Seagate 40M IDE drive in an A1200? Thanks.
>>
>>The default was 0xffffff, I think. I added an extra f for
>>good measure. Was this the right thing to do?

>I don't think so. I've had big problems with the 0xffffff setting on my
>IDE HD. Files bigger than app. 100KB got corrupted when writing to the 
>drive. After reducing the Maxtransfer down to 0xffff all problems 
>dissapeared. I've been told that AT/IDE drives can't handle chunks of data
>bigger than 64KB, therefore one should set the maxtransfer to this value.

On a 1200, MaxTransfer should be 130560 (0xfffe00), or if that gives
problems, 65024 (0xfe00).  Since this is the maximum size for any
transfer, it should be a multiple of 512 (the block size).

IDE drives are supposed to be able to transfer 128k bytes in one chunk,
but because IBM-style disk interfaces don't transfer more than 64k at
a time, some drives have never been tested to more than 64k.  Also, some
drives have problems with an even 128k or 64k, so the suggestions above knock
one extra block off.

>BTW: What does the Memory-Mask mean? Can you change the default value?
>Does it depend on the amount of RAM installed?

The Mask value tells the FileSystem what RAM can be used and how buffers
should be aligned in memory.  It should generally not be changed from
the default of 0x7ffffffe (or 0x00fffffe for an A500/2000 DMA card).

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