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UIDE and AHCI support (Miscellaneous)

posted by Drewfus(R), 27.05.2010, 14:10

> > Jack,
> > what is the possibility for, or status on adding AHCI support to the
> > driver? Is it technically feasible? I enable AHCI on all machines I
> > reimage, and often run DOS diagnostics on the same machines. AHCI
> > support would of course mean that I don't need to switch controller
> modes
> > for DOS/UIDE and then remember to switch back again for Windows.
> Of course I could add AHCI to UIDE -- if I wanted to buy a new system,
> with
> an AHCI mainboard. But in fact I do NOT! NOBODY yet has noted that
> gains ANYTHING in speed/performance and likely IT NEVER WILL, as that
> would
> require something called a "driver" to be written by "Gates & Co."!!
> Does
> the expression "Good LUCK, Sucker!!" mean anything to you??!!
> AHCI's "selling point" is being able to "chain" disk commands and demand
> no
> software handling in-between disk transfers. That is for an
> "asynchronous
> I-O" system like Windows/Unix, NOT for DOS which does one at a time I-O
> and
> CANNOT indicate which of MULTIPLE transfers are COMPLETED, on an
> interrupt!
> So, DOS cannot use "actual" AHCI, and I see NO reason to write 500 bytes
> of
> AHCI run-time logic, plus up to 1000 more of AHCI initialization, into
> only to avoid "switching modes" on DOS/Windows systems. A rather POOR
> use
> of my time!
> I suggest you simply keep your DOS/Windows systems in "compatibility" or
> in
> "legacy IDE" mode, whatever the BIOS guys call it "today"! And I will
> bet
> you lose LITTLE speed/performance, not before "Gates & Co." at-LAST
> "figger
> out" a disk driver WORTH enabling AHCI!! To my knowledge, they still
> have
> NO decent disk driver for SATA/IDE -- Lucho noted to me in 2008, re:
> UIDE's
> performance v.s. Windows "You beat THEM, three MONTHS ago!!" -- and I
> would
> NOT "hold your breath!!" for a decent Windows AHCI driver, either!!

there are web pages that have data that is favourable to AHCI in comparison to IDE mode. See for example:

However, regardless of arguments for or against any performance improvements for AHCI over IDE, what interests me more than this is getting DOS/UIDE to run on existing systems where Windows is preinstalled and AHCI mode is active, without first having to disable AHCI mode manually and having to renable it before rebooting into Windows.

In this sense i like the idea of Laaca, who mentioned that for my purposes it would be adequate to be able to disable AHCI when booting DOS within DOS, and then reenable within DOS before reboot. Given that you've said that DOS does not do asynchronous I-O, and therefore that any theoretical benefits of AHCI are lost in DOS anyway, this idea of quietly disabling/renabling AHCI mode sounds like a good compromise.

So simply put i would appreciate if via UIDE or some other mechanism the following functionality be available for DOS systems.

* Boot DOS
* Save AHCI mode status to environment
* Load UIDE and other drivers
During reboot...
* If AHCI==On AHCI /enable
* Reboot

I hope something like this is feasible without much time or effort.


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