This message is from the T13 list server.
>Curtis Stevens 04/11/02 09:57AM > you pause to look at project 1510D (HBA draft standard) > you will see that it defines PRD mechanisms for both PIO and UDMA... Good to hear. And thanks for the hint! That hint led me to the 21 October 2001: http://www.t13.org/ 1510D ATA/ATAPI Host Adapter Standard Abstract: This standard specifies an Open Host Controller Interface for ATA host adapters. Different types of host adapters, methods for their identification, and the programming interfaces used are defined. ATA/ATAPI Host Adapter Standard is currently under development. The draft document is http://www.t13.org/project/d1510r0b.pdf (255,492 bytes). ... 6.6 PCI Registers ... 10h Base Address 0 -- Base Address of Cmd-Block Regs, ATA Channel X 14h Base Address 1 -- Base Address of Control Regs, ATA Channel X 18h Base Address 2 -- Base Address of Cmd-Block Regs, ATA Channel Y 1Ch Base Address 3 -- Base Address of Control Regs, ATA Channel Y ... which may relate to: to learn to write the boot hd ... the classic [Apple] iMac ... http://members.aol.com/plforth/ofpong/ http://members.aol.com/plforth/moforth/index.html http://members.aol.com/plforth/moforth/20020315/ofide.txt via: Displaying PCI Configuration Registers http://developer.apple.com/qa/qa2001/qa1036.html Thanks again, x4402 Pat LaVarre [EMAIL PROTECTED] http://members.aol.com/plscsi/ >>> Curtis Stevens 04/11/02 09:57AM >>> If you pause to look at project 1510D (HBA draft standard) you will see that it defines PRD mechanisms for both PIO and UDMA... ... -----Original Message----- From: Pat LaVarre [mailto:[EMAIL PROTECTED]] Sent: Wednesday, April 10, 2002 5:57 PM To: [EMAIL PROTECTED] Subject: [t13] Pio by PRD vs. Dma by PRD This message is from the T13 list server. [ BC [EMAIL PROTECTED] since I updated the Subject line. ] > Ok, I meant how is using a PRD list with "PIO" different from "DMA" > (especially from the software perspective) ? Hmmm. I wonder if I'm misunderstanding you? I'm Not trying to be cute or sarcastic ... The low Cpu load is the same, not different. The difference from the host software perspective is that Pio works better than Dma. We can accordingly imagine a PRD list for Pio would work better than a PRD list for Dma. What's happening now is that people write software to talk Pio because it works better than Dma, which makes up for the cost of wasting Cpu cycles on Pio. But that doesn't mean people are happy to waste Cpu cycles. What the people want is Dma that works, and a PRD list for Dma would be a way to deliver that. The commodity Usb/AtapiPio bridges do exactly this: they deliver the Dma experience with Pio cycles at the target. Works great up to burst rates of 17e+6 byte/s. Would be good to see on The Motherboard too. Am I making any more sense yet? Who knows. Maybe serial Ata will learn to count data bytes. Maybe it will learn to copy arbitrary lengths of them from arbitrary addresses. Who knows. x4402 Pat LaVarre [EMAIL PROTECTED] http://members.aol.com/plscsi/ >>> RE: RE: [t13] UDMA Bursts - Pause versus Termination >>> Ooi, Thien Ern 04/10/02 06:19PM >>> This message is from the T13 list server. Ok, I meant how is using a PRD list with "PIO" different from "DMA" (especially from the software perspective) ? -----Original Message----- From: Pat LaVarre [mailto:[EMAIL PROTECTED]] Sent: Wednesday, April 10, 2002 4:38 PM To: [EMAIL PROTECTED] Subject: RE: RE: [t13] UDMA Bursts - Pause versus Termination ... Pio works better than Dma. We know this because we know people use the checkbox that Microsoft provides to turn Dma off. x4402 Pat LaVarre [EMAIL PROTECTED] http://members.aol.com/plscsi/ >>> Ooi, Thien Ern 04/10/02 04:59PM >>> This message is from the T13 list server. I don't understand. How is that different from MW-DMA and UDMA? T.E. -----Original Message----- From: Hale Landis [mailto:[EMAIL PROTECTED]] Sent: Wednesday, April 10, 2002 2:22 PM To: [EMAIL PROTECTED] Subject: RE: RE: [t13] UDMA Bursts - Pause versus Termination ... Another question: Can you give me one good reason why (5 years ago!) the host side should not be able to use a PRD list for PIO data transfers and have the host adapter preform the equivalent of the x86 REP INSx/OUTSx instructions? Given the popularity of ATA/ATAPI and all the improvements done in device designs there is no excuse for the host adapter side of the interface to be in such a sad state! ... *** Hale Landis *** www.ata-atapi.com ***
