Point & Click - Cold Hard Cache For Your GUI
by Clifton Karnes

Whether you're running Windows, GeoWorks Ensemble, or a more exotic graphical user interface, one thing's for sure: You need a disk cache. Why? Because all GUIs are disk-intensive. They simply can't keep everything they offer in the computer's memory, so they routinely swap program code and data from disk to memory and back. Every time your computer reads from the disk, your system slows down. Just how much depends on how fast your hard disk is.

By far, the most cost-effective way to speed up your hard disk is to use a disk cache. This is such an important tool that Windows actually includes a cache as standard equipment, and it automatically installs it for you.

GEOS doesn't come bundled with a cache, probably because its programs run so fast without one. You pay the price for speed, however, when you run a DOS program or shell to DOS. Here GEOS is a tortoise; a cache will dramatically improve its speed.

So, you need a cache. But which one? Windows users get the latest version of SMARTDrive free (it comes with most versions of MSDOS, too), but there are other programs that claim to be better. This month I looked at two: HyperDisk (HyperWare, Route Box 91, Pall Mall, Tennessee 38577; 615-864-6868; $69.00) and Power Cache Plus (Intelligent Devices, 112 Harvard Avenue, Suite 295, Claremont, California 91711; 714-920-9551; $99.95). Both high-performance programs work with Windows, GEOS, and DOS, and both claim to be faster than SMARTDrive.

HyperDisk comes with special versions for conventional memory, 286 systems, and 386 systems. As with most modern caches, it can cache in conventional, expanded, or extended memory, but if your're running Windows, you'll almost certainly want to use extended memory.

Power Cache Plus comes in two versions: PCPFAST offers faster performance, and PCPSMALL is slower but optimized to use less memory. As with HyperDisk, it can cache in conventional expanded, or extended memory.

Power Cache Plus has one incompatibility with Windows: It can't coexist with a permanent swap file. If you run Windows in 386-enhanced mode and use a permanent swap file, you'll take a performance hit by switching to a temporary swap file, as we'll see.

To test these caches, I ran a series of benchmarks in Windows, DOS, and GEOS and found some surprising results.

For the Windows test, I created a macro using PubTech's BatchWorks that opens four applications along with typical documents. I loaded Word for Windows with a 34K document, Microsoft Excel with a 15K spreadsheet, Q+E with a 190K database, and Crosstalk. After each was loaded, its window was resized (with BatchWorks), and then each was closed.

I ran the tests on a Gateway 25-MHz 386 with 4MB of RAM and a 17-ms 110MB hard drive. I set each cache for 1024K using extended memory. In 386-enhanced mode, the suite of Windows programs produced the following times:

No cache 2.08 minutes HyperDisk 1.03 minutes Power Cache Plus 1.68 minutes SMARTDrive 1.13 minutes

Both HyperDisk and SMARTDrive were able to work with a permanent swap file with which Power Cache Plus is incompatible. Because of this, its time suffered. When I tested HyperDisk and SMARTDrive without a permanent swap file, their times were closer to that of Power Cache Plus. Next I tested all three caches in DOS, using the database cache test supplied with Power Cache Plus. Here, the results were amazing. Power Cache Plus averaged more than twice as fast as HyperDisk, and in reading and writing random records, if was more than three times as fast. SMARTDrive and HyperDisk were neck and neck. Average times were:

No cache 6.79 minutes HyperDisk 4.61 minutes Power Cache Plus 2.14 minutes SMARTDrive 4.69 minutes

For GEOS, I tested each cache with a variety of operations: loading GEOS from DOS, running GeoDraw and GeoWrite, and shelling to DOS--one of GEO's slowest operations. Since GEOS is less disk-intensive than Windows, neither cache significantly improved the performance of GEOS applications. But the time it took to shell to DOS and return was more than doubled with both caches. Cache times for these operations were almost identical for HyperDisk, SMARTDrive, and Power Cache Plus.

What does all this mean? If you're using lots of DOS applications and you don't mind not being able to use a permanent swap file in Windows, then power Cache Plus is the choice. If you're not into DOS apps in a big way, then HyperDisk is the winner by a hair. For most of us, SMARTDrive will do just fine, especially if you can afford to give it 1024K of memory.