DOS ain't dead

> 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.

> 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 ?

Yes, Win98 booted in INT13h compatability mode but disk operations was extremely slow about 1MB/s. And windows gives you warnig that disk subsys run in 16bit mode. Normally in IDE compatability mode I can reach ~30MB/s copying speed.

---
DOS gives me freedom to unlimited HW access.

> Thanks for explanation. BTW is the driver specific for each controller
> model (e.g. ICH7, ICH8,...) or it works samo on whole ICHx family?

AHCI is its own standard, so any software written to work on say, the ICH9 AHCI controller should also work on a JMicron AHCI controler, or an ICH10 controller too. Vendors may add their own features to their controllers, and thus want their own driver to take advantage of those features though, and that would be outside of our DOS world without the chipset specifications. The AHCI spec is however available to the public, and that's what I wrote my software against.

Key word there is *should* ;)

> Thanks for explanation. BTW is the driver specific for each controller
> model (e.g. ICH7, ICH8,...) or it works samo on whole ICHx family? Yes it
> would be nice for ghost or pqmagic clone. But this sw are not opensource.
> I think Ghost is very rich of features and also has nice GUI and it will
> be hard to make such well opensrc program. If ghost would allow to use
> some external disk driver with documented api it will be much easier...

Older ICH's like ICH8 don't support AHCI. ICH8R should though, and there have been rumours that the ICH8R drivers can be tweaked to support ICH8, but I haven't seen real confirmation. (the JMicron on the same board did support AHCI and NCQ though (MSI p965 neo-F), would have to look up the exact chipnr)

While messing with an external ESATA bracket, I blew up my ICH8 though, so I'm now at ICH10R

> Hello
> I'm interested about your ahci code.
> I'm not a programmer and I have trying to enable ahci on some notebook but
> vendor doesn't provide this option in bios.
> I have managed through a pci option rom to rewrite ICH7-M registers to
> switch controller in ahci mode but then bios can't boot from fixed disk.
> But if I boot from usb some linux distro I can see is in ahci mode and can
> get access to disk.
> That explain why I'm intersted about your ahci code.
> I hope this will help somehow in my tries to regain access to boot from
> disk.
> Thanks.
> I forget to say,I have tested also with AHCCMDT from ata-atapi.com and
> their software can find and gain access to disk when I use this trick to
> switch controller to ahci but is only for testing.

Hmmm.
So my code would have to be converted into a BIOS int-13 extension loaded through your PCI option rom. that would allow you to boot the device, then your OS would load an ahci driver. If you are only using DOS for your OS, no driver would be required. Doable I think, but I doubt performance would be any better. Performance is only better when you can utilize a lot of system memory and have many outstanding IO requests at a time.

I don't have the time to work on it though, and whoever did do this would need the hardware to test it with-this is not something I could write at home and just send to you without many hours of debugging.

I guess I have to ask what/why are you trying to achieve with this setup?