[ltp] "80-wire cables" issue when using SATA drives in PATA Thinkpads

[Stefan Monnier]

Henrique de Moraes Holschuh [2021-01-29 20:18:50] wrote:
> On Mon, 12 Oct 2020, Stefan Monnier wrote:
> But that patch basically just did what libata.force does: you'd get
> UDMA5 all the time, just like you get with libata.force=80c.
>
>> I tried to boot with `libata.force=80c` and it does result in `hdparm`
>> showing me that `udma5` is used instead of `udma2`, but that seems to be
>> a lie because the actual bandwidth I see is still ~30MB/s.
>
> This is likely the fault of the PATA-SATA bridge.

I finally discovered that while `hdparm -tT` is not able to get more
than about 30MB/s, both with or without the `libata.force=80c`, I was
finally able to get more than 40MB/s in other circumstances with
`libata.force=80c`.

This thus confirms that `libata.force=80c` does indeed lift the 33MB/s
limit and that the bandwidth I'm seeing is limited elsewhere (most
likely the poor Thinpad itself).

Thanks for bearing with me,


        Stefan