Re: SCSI I/O errors galore, PART II
> > Seems in this case it can't. My external disk only runs at 5 MB (of
> > course).
> >
> > How to set MESH to 5 MB/s? I'd not object to providing a patch that makes
> > it a driver option, if someone can point me to the correct combinattion of
> > period and offset to limit the rate.
>
> Eternal is different. Since Apple wisely decided on a 25-pin scsi
> cable scheme for external disks, they can only get up to 5MB/s
> there. [Sarcasm] So they used a separate controller for that. The
Nope, not on a Powerbook at least.
> NCR 53Cwhatever. Anyway, that controller is what drives the second
> "slow" connector on the mobo's that have it, as well as the external
> 25pin connector. Why Apple did it this way is beyond me and seems
> so collosally stupid that there is just no way to explain it.
> Perhaps real 50 pin cables were deemed too expensive or something.
All Macs ever had was the 25 pin connectors, call it back(*ss)wards
compatibility.
> A former author of the linux driver for the aic7xxx series of scsi
> controllers once tried to explain exactly how NCR and apple managed
> to hack the scsi standard to get a 25 pin cable to work with drives
> that have a 50pin connector, but he got so upset about the whole
the 50 pin connectors are half ground (signal return) wires for single
ended SCSI. Differential, that would be atrocious.
> Suffice it to say that if your disk can't do over 5MB/s then you
> have nothing to do or worry about.
Yep, but I've always had the driver throttled to 5 MB anyways. I've
totally forgotten about that compile time option (thanks Geert, I finally
figured out how the sync period is calculated). Time to turn it into a
runtime option I guess, that might be easier than distributing two kernel
images. Opinions, anyone?
Michael
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