Question about dma settings

[Nelly]

hi all,
i just put together an asus a7m266,1ghz(266)t-bird,512mb pc2100(crucial),maxtor 20gb(m),40gb(s),creative 12dvd(m),creative 12x10x32 cdrw(s),sb live val.,ati radeon 64mb ddr...the dvd is set to dma mode 2 in the bios but i am unable to set the cdrw.it always defaults back to mode4. anyone have any ideas why? and is this important?on this puter(p3v4x,sony-cdrw)both are dma enabled.on another p3v4x i built with an hp cdrw it was again set to mode4.what the heck is mode 4?
thanks in advance,
Nelly

[glc]

Mode 4 is standard IDE, so to speak. DMA 2 is Ultra 33 - and if the CD only wants to be Mode 4, that's all it's capable of. You can't force it to be something it isn't. This has *nothing* to do with "enabling DMA" on the drives.

[Nelly]

thanks glc,
this means that if i choose dma under windows Me it will functiuon in dma mode?
TY
Nelly

[glc]

Yes.

[muckshifter]

IDE - Integrated Drive Electronics - Any drive with an integrated controller. This means that most of the control circuitry is built into your "IDE Drive", and not on the controller. Most of us consider any ATA drive to be an "IDE Drive".

ATA - Stands for Advanced Technology Attachment. ATA drives are a subset of IDE drives and use a 40 Pin connector. ATA is used interchangeably (even incorrectly) as a substitute for IDE (ATA Drive = IDE Drive).

PIO Mode - Programmed I/O Mode. Defines the I/O Mode in which an ATA hard drive runs. Basically determines the speed at which the bus is run. The higher the PIO mode, the higher the bus speed. PIO modes went out when UDMA came in, and this term is becoming obsolete.

DMA - Direct Memory Access. Allows a device direct access to main memory, bypassing the CPU. This allows for faster transfers, and takes a lot of the load off of the CPU.

"IDE" Drives
While an IDE drive is actually any drive with a controller built in, we use this term to designate most of the hard disk drives we use today. Actually, what we usually call "IDE drives" would really better be called "ATA Drives" as ATA is the interface (similar to SCSI) that "IDE drives" use.

While most of the drives we use now are Ultra DMA, many of us remember using "mode 3" or "mode 4" hard drives. These were ATA-2 drives, using PIO mode 3 or mode 4. Here's a table of the evolution of the ATA Interface since 1993:

Interface Type
ATA-2 PIO 3 13.3MB/s 1993
ATA-2 PIO 4 16.6MB/s 1994
UDMA/33 33.3MB/s 1997
UDMA/66 66.6MB/s 1999

UDMA
As drive technology got better and areal densities started rising at rates faster than 20% per year, the need for a new standard emerged. One that would allow 2 devices to share an ATA chain comfortably, and still have room to breathe. With current hard drives reaching sustained transfers up in the 10MB/sec range, obviously a 16.6MB/sec bus would not have sufficed. Before these speeds were attained, however, Quantum developed the Ultra-ATA/33 standard (UDMA/33). To obtain the 33MB/sec speeds, the clock signal was kept the same, but data was now transferred on the rising AND falling edges of the clock, rather than just the rising. While this was cozy for a little while, it was not long before drive technology was growing faster than the new interface could handle.

Ultra DMA/66
As areal densities rose and rotational speeds jumped, hard drive manufacturers once again saw the need for a new standard. Similarly to UDMA/33, Ultra DMA/66 once again doubled the maximum capacity of the IDE chain. To do this, the clock speed halved, this time to 30ns, and a few problems arose. With such fast clock speeds across such a long bus, noise becomes an increasing problem. To combat this, an 80 wire model was created, and that is why UDMA/66 cables are different than anything we have seen for ATA drives in the last 6 or 7 years.

All UDMA/66 drives are capable of running on your legacy ATA chains, and you can even run legacy ATA drives on your UDMA/66 chains. Without the 80-wire cable, however, you will not get the "advantages" of the UDMA/66 devices.

UDMA drives offer more than just a bandwidth increase, however. They also increase the reliability of data, by adding a CRC calculation to the standard. Whenever data is sent to a drive operating in UDMA mode, it will error check the data, and if an error occurs, the data will be resent at a slower transfer mode. When all is said and done, however, in a single drive system, or even for most of us in a dual drive system, the gains are minimal, and upgrading the drive is likely more important than upgrading the controller.

All UDMA/66 drives are capable of running on your legacy ATA chains, and you can even run legacy ATA drives on your UDMA/66 chains. Without the 80-wire cable, however, you will not get the "advantages" of the UDMA/66 devices.

I do hope that was usefull.

[Nelly]

well thank you muck,all...
does the fact that my cdrw is not set to dma in the bios going to have any effect on how it operates in Win ME?(it IS checked for the drive in ME)its a brand new drive so i'm just bugged as to why it doesn't say dma in the bios...i just sent an email to soundblaster support to see if i can get a response from them.i'll post when i get a reply for fyi for everyone.
thanks,
Nelly

[muckshifter]

Good luck in getting a response from Creative.

You do not need to set DMA in the BIOS (indeed some mobo’s do not have a setting in the BIOS). If it is set to DMA in WinME then give it a whirl. If you suffer from any reading problems, while using the drive, then un-tick DMA mode & try again.

Creative should stick to producing sound cards, but then you have to diversify to stay in business.

good luck.

[glc]

DMA in the bios has NOTHING to do with DMA in Windows. You cannot set a PIO Mode 4 device to DMA in the bios. The drive will detect as what it is. I know of NO cd readers or cd burners that are UDMA - just some DVD drives, and they are only UDMA 2. What's the problem? Just enable DMA in Windows for all your drives. DMA and UDMA aren't the same thing really. UDMA is just another term for "Ultra ATA". DMA is Direct Memory Access.

I have two Ultra ATA33 hard drives - and the bios reports them as Mode 4 UDMA 2. My 24x CD reader reports as Mode 4 and my 2x CD burner reports as Mode 3. Thats exactly what they are - and there is no way to get them to report as anything else unless I SLOW things down in the bios - and why would I want to do this?