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Written By: Keith "Farrel" McClellan
Posted: February 29, 2000
Having hard drive and memory tweaks in the same guide seems like an odd marriage, but believe it or not, they overlap in quite a few ways. Hard drives have a feature commonly referred to as DMA, or direct memory access. Your system's RAM partitions out part of itself for its VCache, or virtual cache, in which it keeps data from the hard drive. And the hard drive itself can actually "become" RAM when it's used for Virtual Memory. Suffice it to say, these topics fit together so well that it is almost impossible to separate them out, so why bother trying?
Note: These tweaks are written with Windows 98 and above in mind. If you are running Windows 95, be even more cautious than usual.
Direct Memory Access
DMA is one of the biggest tweaks you can do for your Hard Drive and Memory subsystems, because it allows the computer to circumvent the CPU when loading data into memory from the hard drive. Before continuing with these tweaks, however, be forewarned that enabling DMA on a drive that doesn't support it is very dangerous, so unless you are SURE that DMA is supported, forego these tweaks. It should be pointed out that just about all 5400 and 7200-rpm hard drives, and even many lower speed drives, support DMA.
If you are unable to get the appropriate information off of the manufacturers website, check out Windows-help.net, which includes several tests to determine DMA compatibility.
Within the BIOS, make sure your hard drive is configured to Master (if possible) and that any supported UDMA settings are turned on. If you aren't sure if your hard drive supports UDMA (or your BIOS doesn't have the setting), try out the settings first using TweakBIOS. This program may also help you configure your hard drive when used on an overclocked system (covered later in the guide).
To enable DMA within Windows 9x, go to the Control Panel / System applet (Start -> Settings -> Control Panel -> System) and go to the Device Manager tab. Under the Disk Drive subheading, choose the listing of your hard drive and open it by double clicking on it. Go to the settings tab and make sure that DMA is enabled. To make sure that DMA doesn't cause any internal Windows conflicts (assuming the drive supports DMA), you are going to need to add these lines to the Mshdc.inf file at the bottom of the [ESDI_AddReg] tag (if they aren't already there):
Only add the bottom two lines (the bolded ones) if you have more than two IDE drives (HD/CD devices) connected to your system. Within the DISKDRV.INF file, add the same lines under the [DiskReg] entry. If the lines are already there, you don't need to continue on, because you are done. Otherwise, copy the two modified files to another directory (I recommend creating a new directory named inf2 in your windows system directory) and remove all of the items under the Hard Drive Controllers and all of the Hard Drives (only hard drives, not removable media) from under the Disk Drives heading. Then reboot your system. When the computer's Hardware Wizard pops up to reinstall the drives, set it so you can choose from the compatible drivers list and check the date on the drivers. They should be for the same day you modified them. If they are, great, use them, otherwise you will need to point them at the copies (the inf folder is invisible at this point, which is why you need the second copies) and use those. I grabbed the extra information about this tweak from Super7.net. Thanks guys!