Solved

Theoratical DMA question

Posted on 1998-05-29
3
339 Views
Last Modified: 2010-04-27
Hi,
    I have a question regarding DMAs. I understand the concept that the DMA is used to organise the movement of data so that the processor can get on with processing it. What are the implications if 2 DMAs are used? Is there any sort of limit to the number of DMAs you could use? Would it cause bigger problems with keeping the cache consistent?
Thanks in advance,
Nik.
0
Comment
Question by:PiersBull
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
3 Comments
 
LVL 2

Accepted Solution

by:
datn earned 100 total points
ID: 1135682
DMA or direct memory access are used by high speed devices that bypasses the CPU, therefore, "direct". Serial and parallel ports are not DMA, but sound cards and SCSI cards often are. In IBM-AT compatible machines, you have access to 7 DMA channels. If you have the same DMA channel being used at the same time, you will have a resource conflict. However, if the devices do not need the DMA simultaneously, it is possible to share the DMA. For example, if you have a tape backup and a network adapter, you can do backups, but not while being on the network.
0
 

Author Comment

by:PiersBull
ID: 1135683
Hi datn,
    Does 7 DMA channels imply that there are 7 DMAs? i.e. 7 seperate pieces of hardware?

Cheers.
0
 
LVL 2

Expert Comment

by:datn
ID: 1135684
You actually have two DMA controllers per card. The first 4 DMA does transfers at 8-bit, while the 2nd 4 DMA has 16-bit transfers. Channel 0 does not appear on most 16-bit cards. If it does, it still only transfers data at 8-bits. Channel 1 and 5 are usually for the sound, with channel 5 being only 16-bit. Channel 2 is universally used by the floppy controller. Channel 3 is for ECP parallel ports. Channel 6 is available usually as a SCSI. Channel 7 is also a 16-bit available.
0

Featured Post

Revamp Your Training Process

Drastically shorten your training time with WalkMe's advanced online training solution that Guides your trainees to action.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

this article is a guided solution for most of the common server issues in server hardware tasks we are facing in our routine job works. the topics in the following article covered are, 1) dell hardware raidlevel (Perc) 2) adding HDD 3) how t…
Every server (virtual or physical) needs a console: and the console can be provided through hardware directly connected, software for remote connections, local connections, through a KVM, etc. This document explains the different types of consol…
Michael from AdRem Software outlines event notifications and Automatic Corrective Actions in network monitoring. Automatic Corrective Actions are scripts, which can automatically run upon discovery of a certain undesirable condition in your network.…
This is my first video review of Microsoft Bookings, I will be doing a part two with a bit more information, but wanted to get this out to you folks.

705 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question