> Can you try with kernel parameter 'acpi=noirq' or 'irqpoll'?
I made a typo when passing the irqpoll parameter to the kernel. In 
kernel 2.6.20.4 with the irqpoll parameter passewd to kernel the SATA 
disk works:

[    1.320000] ide: Assuming 33MHz system bus speed for PIO modes; 
override with idebus=xx
[    1.320000] ahci 0000:00:12.0: version 2.0
[    1.320000] ACPI: PCI Interrupt 0000:00:12.0[A] -> GSI 22 (level, 
low) -> IRQ 16
[    2.324000] ahci 0000:00:12.0: AHCI 0001.0100 32 slots 4 ports 3 Gbps 
0xf impl SATA mode
[    2.324000] ahci 0000:00:12.0: flags: 64bit ncq ilck pm led clo pmp 
pio slum part
[    2.324000] ata1: SATA max UDMA/133 cmd 0xF8824D00 ctl 0x0 bmdma 0x0 
irq 222
[    2.324000] ata2: SATA max UDMA/133 cmd 0xF8824D80 ctl 0x0 bmdma 0x0 
irq 222
[    2.324000] ata3: SATA max UDMA/133 cmd 0xF8824E00 ctl 0x0 bmdma 0x0 
irq 222
[    2.324000] ata4: SATA max UDMA/133 cmd 0xF8824E80 ctl 0x0 bmdma 0x0 
irq 222
[    2.324000] scsi0 : ahci
[    2.636000] ata1: SATA link down (SStatus 0 SControl 300)
[    2.636000] scsi1 : ahci
[    3.120000] ata2: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
[    3.136000] ata2.00: ATA-7, max UDMA/133, 160836480 sectors: LBA48 
NCQ (depth 31/32)
[    3.136000] ata2.00: ata2: dev 0 multi count 16
[    3.144000] ata2.00: configured for UDMA/133
[    3.144000] scsi2 : ahci
[    3.456000] ata3: SATA link down (SStatus 0 SControl 300)
[    3.456000] scsi3 : ahci
[    3.768000] ata4: SATA link down (SStatus 0 SControl 300)
[    3.768000] scsi 1:0:0:0: Direct-Access     ATA      HDS728080PLA380  
PF2O PQ: 0 ANSI: 5
[    3.768000] PNP: PS/2 Controller [PNP0303:PS2K,PNP0f03:PS2M] at 
0x60,0x64 irq 1,12
[    3.768000] serio: i8042 KBD port at 0x60,0x64 irq 1
[    3.768000] serio: i8042 AUX port at 0x60,0x64 irq 12
[    3.768000] mice: PS/2 mouse device common for all mice
[    3.768000] EISA: Probing bus 0 at eisa.0
[    3.768000] EISA: Detected 0 cards.
[    3.792000] input: AT Translated Set 2 keyboard as /class/input/input0
[    3.800000] TCP cubic registered
[    3.800000] NET: Registered protocol family 1
[    3.800000] Starting balanced_irq
[    3.800000] Using IPI No-Shortcut mode
[    3.800000] ACPI: (supports S0 S1 S3 S4 S5)
[    3.800000] Freeing unused kernel memory: 316k freed
[    3.804000] Time: hpet clocksource has been installed.
[    3.876000] ACPI: duty_cycle spans bit 4
[    4.268000] SCSI device sda: 160836480 512-byte hdwr sectors (82348 MB)
[    4.268000] sda: Write Protect is off
[    4.268000] sda: Mode Sense: 00 3a 00 00
[    4.268000] SCSI device sda: write cache: enabled, read cache: 
enabled, doesn't support DPO or FUA
[    4.268000] SCSI device sda: 160836480 512-byte hdwr sectors (82348 MB)
[    4.268000] sda: Write Protect is off
[    4.268000] sda: Mode Sense: 00 3a 00 00
[    4.268000] SCSI device sda: write cache: enabled, read cache: 
enabled, doesn't support DPO or FUA
[    4.268000]  sda: sda1
[    4.292000] sd 1:0:0:0: Attached scsi disk sda

And the disk (lshw):

       *-storage
             description: SATA controller
             product: SB600 Non-Raid-5 SATA
             vendor: ATI Technologies Inc
             physical id: 12
             bus info: pci@00:12.0
             logical name: scsi1
             version: 00
             width: 32 bits
             clock: 66MHz
             capabilities: storage ahci_1.0 bus_master cap_list emulated
             configuration: driver=ahci
             resources: ioport:e800-e807 ioport:e400-e403 
ioport:e000-e007 ioport:dc00-dc03 ioport:d800-d80f 
iomemory:febffc00-febfffff irq:222
           *-disk
                description: SCSI Disk
                product: HDS728080PLA380
                vendor: ATA
                physical id: 0.0.0
                bus info: scsi@1:0.0.0
                logical name: /dev/sda
                version: PF2O
                serial: PFDH37SYTWKR9E
                size: 76GB
                capabilities: partitioned partitioned:dos
                configuration: ansiversion=5

Nice isn't it? I'm happy.

In the 2.6.21-rc5 version this hasn't worked (the typo was here too, 
copy, paste & destroy :P). Here's is the output of dmesg:

[    1.336000] ide: Assuming 33MHz system bus speed for PIO modes; 
override with idebus=xx
[    1.340000] ahci 0000:00:12.0: version 2.1
[    1.340000] ACPI: PCI Interrupt 0000:00:12.0[A] -> GSI 22 (level, 
low) -> IRQ 16
[    2.344000] ahci 0000:00:12.0: AHCI 0001.0100 32 slots 4 ports 3 Gbps 
0xf impl SATA mode
[    2.344000] ahci 0000:00:12.0: flags: 64bit ncq ilck pm led clo pmp 
pio slum part
[    2.344000] ata1: SATA max UDMA/133 cmd 0xf8824d00 ctl 0x00000000 
bmdma 0x00000000 irq 222
[    2.344000] ata2: SATA max UDMA/133 cmd 0xf8824d80 ctl 0x00000000 
bmdma 0x00000000 irq 222
[    2.344000] ata3: SATA max UDMA/133 cmd 0xf8824e00 ctl 0x00000000 
bmdma 0x00000000 irq 222
[    2.344000] ata4: SATA max UDMA/133 cmd 0xf8824e80 ctl 0x00000000 
bmdma 0x00000000 irq 222
[    2.344000] scsi0 : ahci
[    2.656000] ata1: SATA link down (SStatus 0 SControl 300)
[    2.656000] scsi1 : ahci
[    3.140000] ata2: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
[   33.140000] ata2.00: qc timeout (cmd 0xec)
[   33.140000] ata2.00: failed to IDENTIFY (I/O error, err_mask=0x104)
[   34.120000] ata2: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
[   64.120000] ata2.00: qc timeout (cmd 0xec)
[   64.120000] ata2.00: failed to IDENTIFY (I/O error, err_mask=0x104)
[   64.120000] ata2.00: limiting speed to UDMA7:PIO5
[   65.100000] ata2: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
[   95.100000] ata2.00: qc timeout (cmd 0xec)
[   95.100000] ata2.00: failed to IDENTIFY (I/O error, err_mask=0x104)
[   96.080000] ata2: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
[   96.080000] scsi2 : ahci
[   96.392000] ata3: SATA link down (SStatus 0 SControl 300)
[   96.392000] scsi3 : ahci
[   96.704000] ata4: SATA link down (SStatus 0 SControl 300)
[   96.704000] PNP: PS/2 Controller [PNP0303:PS2K,PNP0f03:PS2M] at 
0x60,0x64 irq 1,12
[   96.704000] serio: i8042 KBD port at 0x60,0x64 irq 1
[   96.704000] serio: i8042 AUX port at 0x60,0x64 irq 12
[   96.704000] mice: PS/2 mouse device common for all mice
[   96.704000] EISA: Probing bus 0 at eisa.0
[   96.704000] EISA: Detected 0 cards.
[   96.704000] TCP cubic registered
[   96.704000] NET: Registered protocol family 1
[   96.704000] Starting balanced_irq
[   96.704000] Using IPI No-Shortcut mode
[   96.708000] Freeing unused kernel memory: 332k freed
[   96.724000] input: AT Translated Set 2 keyboard as /class/input/input0
[   96.780000] ACPI: duty_cycle spans bit 4
[   97.236000] SB600_PATA: IDE controller at PCI slot 0000:00:14.1
[   97.240000] ACPI: PCI Interrupt 0000:00:14.1[A] -> GSI 16 (level, 
low) -> IRQ 17
[   97.240000] SB600_PATA: chipset revision 0
[   97.240000] SB600_PATA: not 100% native mode: will probe irqs later
[   97.240000]     ide0: BM-DMA at 0xff00-0xff07, BIOS settings: 
hda:DMA, hdb:DMA
[   97.240000] Probing IDE interface ide0...
[   97.528000] hda: HDS728080PLAT20, ATA DISK drive
[   97.976000] hdb: ASUS DRW-1608P3S, ATAPI CD/DVD-ROM drive
[   98.032000] ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
[   98.052000] hda: max request size: 512KiB
[   98.056000] hda: 160836480 sectors (82348 MB) w/1719KiB Cache, 
CHS=16383/255/63, UDMA(100)
[   98.056000] hda: cache flushes supported
[   98.056000]  hda: hda1 hda2 < hda5 hda6 >
[   98.108000] hdb: ATAPI 63X DVD-ROM DVD-R-RAM CD-R/RW drive, 2000kB 
Cache, UDMA(66)
[   98.108000] Uniform CD-ROM driver Revision: 3.20
[   98.356000] Probing IDE interface ide1...


Why this happens? Any clue?

I attached those files too so you can take a better look at them. Thanks!

Matías