pozar@kumr.UUCP (Tim Pozar) (10/19/90)
I am currently working on a driver for a very fast serial port.
I am interested in using one of the DMA channels on the AT. (I expect
that this driver will be used on mainly '386 systems.) I am trying
to find out what has been assigned to which channels on the DMA(s) on
the XT and AT.
Also, I noticed that TOPS's flashcard uses a default of channel
1 at the address of 398. Is this a pretty safe address to use?
I tried to track some of this down via the IBM XT tech manual and
a number of other books like Norton's and Duncan's, but to no avail.
I also checked out the latest Interrupt file (590) with VERY sparce
info on DMAs (read: useless for this project). Is there another
reference I should seek?
Thanks for any help...
Tim
---
uunet!hoptoad!kumr!pozar Fido: 1:125/555 PaBell: (415) 788-3904
USNail: KKSF-FM / 77 Maiden Lane / San Francisco CA 94108
"The nice thing about standards is that you have so many to choose from.
Futhermore, if you don't like any of them, you can just wait for next
year's model."
-- Andrew S. Tanenbaum, "Computer Networks" (4.7.1)lsalomo@omni.uucp (Lawrence W Salomon) (10/21/90)
If I recall, there are three DMA channels on the chip (and if you have an AT, then I think you can two chips). Channel 2, I believe, is used for memory refresh, since the PC uses dynamic RAM; channel 3, I believe, is used for the disk controller; that leaves channel 1. Of course, it has been a LONG time since I have messed with the DMA controller, and I don't have my handy references with me... Cheers, Q - the "Q"uestor for knowledge (, a degree, etc.) lsalomo@hubcap.clemson.edu ibmman@prism.clemson.edu ibmman@clemson.clemson.edu ============================================================================= "Gee Wally, I think there's something wrong with the Beaver." =============================================================================
james@bigtex.cactus.org (James Van Artsdalen) (10/22/90)
In <11055@hubcap.clemson.edu>, lsalomo@omni.UUCP (Lawrence W Salomon) wrote: > If I recall, there are three DMA channels on the chip (and if you > have an AT, then I think you can two chips). Channel 2, I believe, is > used for memory refresh, since the PC uses dynamic RAM; DMA 2 is the floppy drive. Refresh doesn't use DMA any more. -- James R. Van Artsdalen james@bigtex.cactus.org "Live Free or Die" Dell Computer Co 9505 Arboretum Blvd Austin TX 78759 512-338-8789
bote@csense.uucp (John Boteler) (10/27/90)
pozar@kumr.UUCP (Tim Pozar) claimed: > I am currently working on a driver for a very fast serial port. >I am interested in using one of the DMA channels on the AT. (I expect >that this driver will be used on mainly '386 systems.) I am trying >to find out what has been assigned to which channels on the DMA(s) on >the XT and AT. That's gotta be one helluva fast serial port! Being a good programmer :) I am sure that you will provide the user the option of selecting these parameters, rather than hard coding them into your driver. If it helps you, the Adaptec 1540B SCSI host adapter I just installed uses DMA channel 5, with jumper options to select many other channels. I believe there to be many more DMA channels provided on AT class systems than there were on the now-ancient PC class architecture. Good luck. -- John Boteler bote@csense {uunet | ka3ovk}!media!csense!bote SkinnyDipper's Hotline: 703 241 BARE | VOICE only, Touch-Tone(TM) signalling