DOS ain't dead

AHCI CD-ROM driver for DOS (Developers)

posted by DOSferatu, minneapolis, mn usa, 18.12.2009, 16:04

> So with AHCI enabled you have INT $13 and AHCI available, but no IDE PIO
> and no IDE UDMA ? And this 98SSE can'u use INT $13 ?

I'm sure the specifics are different for each vendor's implementation of their INT 13 wrapper, but essentially in AHCI mode:

1) there are no longer IO ports to access the drive. (1f0-1f7, 170-177, etc) so the drive does not appear as a standard hard drive anymore.

2) all of the access to the drive is done through DMA through the AHCI controller itself. essentially the "driver" or int 13 interface takes a command, even identify device, which is PIO, and you build a bunch of tables in memory that tell the controller what the command is, where to get/put the data, etc, then you hit the "go" bit, and the controller takes care of the actual drive communication through DMA.

The performance of AHCI comes through a parallel interface in these tables you can build. You can have 32 outstanding requests at the same time, each with their own scatter/gather tables and buffers in memory.
You build the tables of the commands you want to issue, hit that go bit and sit back and wait for your data to be read or written to/from the drive. (I think you can do up to 32mb sized transfers, and have 32 of them at a time.)

3) my assumption would be that when using the INT13 interface, they probably don't open up 32 channels, as that becomes a big memory hog and could require memory access >1mb. My guess is that it's only 1 channel ever being used, and thus with 1 channel going, you'd end up with the exact same performance as issuing commands to a standard SATA port.

Complete thread:

• AHCI projects? - DOSferatu, 14.12.2009, 20:30 (Developers)
  • AHCI CD-ROM driver for DOS - Rugxulo, 15.12.2009, 02:10
    • AHCI CD-ROM driver for DOS - RayeR, 16.12.2009, 01:37
      • AHCI CD-ROM driver for DOS - RayeR, 16.12.2009, 01:45
      • AHCI CD-ROM driver for DOS - DOS386, 18.12.2009, 02:09
        • AHCI CD-ROM driver for DOS - DOSferatu, 18.12.2009, 16:04
          • AHCI CD-ROM driver for DOS - DOS386, 19.12.2009, 04:08
            • AHCI CD-ROM driver for DOS - DOSferatu, 21.12.2009, 16:45
              • AHCI CD-ROM driver for DOS - DOS386, 22.12.2009, 17:11
        • AHCI CD-ROM driver for DOS - RayeR, 19.12.2009, 20:27
          • AHCI CD-ROM driver for DOS - DOS386, 20.12.2009, 08:05
  • AHCI projects? - Maybe Jack R. Ellis!! - swf, 16.12.2009, 01:05
  • AHCI projects? - Khusraw, 16.12.2009, 11:54
    • AHCI projects? - DOSferatu, 16.12.2009, 15:56
      • AHCI projects? - RayeR, 16.12.2009, 18:10
        • AHCI projects? - DOSferatu, 16.12.2009, 22:21
        • AHCI projects? - marcov, 17.12.2009, 10:25
          • AHCI projects? - RayeR, 19.12.2009, 20:37
            • AHCI projects? - marcov, 17.01.2010, 14:34
              • AHCI projects? - Laaca, 08.03.2010, 09:41
                • AHCI projects? - DOSferatu, 10.03.2010, 16:57
                  • AHCI projects? | Sound - DOS386, 17.03.2010, 05:53
                    • AHCI projects? | Sound - DOSferatu, 17.03.2010, 22:34
                      • AHCI projects? | Sound | Mail theft - DOS386, 18.03.2010, 09:36
      • AHCI projects? - Gabiz_ro, 27.03.2010, 22:45
        • AHCI projects? - DOSferatu, 31.03.2010, 15:59
          • AHCI projects? - Gabiz_ro, 01.04.2010, 19:00
      • AHCI projects? - Gabiz_ro, 07.04.2010, 22:58
      • AHCI projects? - kladno, 06.05.2010, 08:40
  • AHCI projects? - mcluskyism, 06.05.2023, 09:37
    • AHCI projects? - glennmcc, 07.05.2023, 21:04
      • AHCI projects? - mcluskyism, 08.05.2023, 17:28
    • AHCI projects? - mcluskyism, 13.05.2023, 13:27