H O W - T O USERS

Upgrading System Memory

by Daniel Miles Kehoe

There's a simple rule of thumb with NeXTSTEP: The more memory you plug into your computer, the faster it will run. NeXT says that 8MB is enough for most applications that most users want to run. But running NeXTSTEP on an 8MB system is tight. By itself, the Mach kernel takes up 1.5MB. The Display Post-Script Window Server takes up another three or four, and Work-space Manager another two. That leaves only 2MB or so for your applications before your computer starts doing more paging (swapping programs to disk) than thinking.

With an 8MB system, you'll hear your hard disk rattle every time you switch between application programs. This becomes less noticeable on a 16MB system and all but vanishes on systems with more memory.

Shopping for memory
If price is a factor in your purchase decision, you'll want to consider mail-order memory merchants. These suppliers buy carloads of raw chips from Japan, insert them on tiny SIMM circuit boards, and sell their wares cheaply. Unfortunately, not every memory merchant sells SIMMs that fit the NeXT, and many vendors cannot provide proper technical assistance for NeXT users. But if you find a mail-order vendor with whom you are comfortable, chances are good that it will offer a competitive price. As this is written, you can purchase 4MB SIMMs for 25MHz monochrome NeXT-stations for about $100 and 8MB SIMMs for Turbo Color systems for about $225.

Different NeXT systems require different SIMM types. For a 16MB memory upgrade of older (motherboard serial number AB0028000 or lower) monochrome 25MHz NeXTstations, you need four, 4MB nonparity, 4-by-8, 80-nanosecond (or faster), vertically mounted, 30-pin SIMMs. The same SIMMs can be used in an '030 NeXTcube, but they must be low-profile parts, with a height that does not exceed 0.9 inches. (These are the same SIMMs that are used in many Macintoshes, but not the Mac IIfx.)

For an 8MB memory upgrade for a NeXTstation Color, NeXTstation Turbo (either monochrome or color), or newer NeXTstations, you need two 4MB nonparity, 1-by-32, 72-pin, 70-nanosecond (or faster) SIMMs. Both single- and double-sided SIMMs are compatible.

Check for a year (or longer) guarantee, a 14-day swap policy (should a new SIMM be dead on arrival), and immediate availability. If you're buying mail-order, be prepared to pay extra for the privilege of using a charge card.

Parity
Parity SIMMs have an extra bit that the NeXT computer uses to check for errors as data is read out of memory. NeXT '040 computers automatically detect the ninth bit and use it. Using parity SIMMs increases the reliability of your computer: If a memory error occurs, your computer will instantly crash, easily alerting you to a problem. Without parity SIMMs, your computer might continue to hobble along with memory errors; some applications might mysteriously fail while others might corrupt data.

On 25MHz NeXTstations, parity memory runs slightly slower than nonparity. Parity checking is done in parallel on the new Turbo systems, so there is no performance penalty for using it. If you want to be absolutely sure of your system's integrity, get parity memory. For ordinary applications, parity memory is not needed.

Rolling up your sleeves
NeXT's official position on user-installed memory is simple: "Upgrades should be performed only by an Authorized Service Provider."

That doesn't mean you can't use third-party memory. Even going by the letter of the law, you can order memory from a trustworthy mail-order house and pay your authorized reseller's standard rate for labor. Your reseller may raise an eyebrow but will probably do the work when paid.

On the other hand, you might try to do your own upgrade. But be warned: Do any damage, and you'll void NeXT's warranty.

Installing memory
Static electricity destroys memory chips. To be free of unwanted sparks as you move about the inside of your computer, you should don an antistatic wrist strap and connect it to the computer. Radio Shack � and memory vendors � sell antistatic straps for a few dollars. Upgrading an 8MB monochrome NeXTstation requires that you remove the four SIMMs nearest the computer's power supply. A SIMM-removal tool, which looks a lot like a dentist's pick, is absolutely necessary. Never use a screwdriver to pry out SIMMs.

Carefully press the new SIMMs into place, making sure they're fully seated. Finally, replace the cover and plug back in the computer. Close up the computer and the NeXT automatically recognizes its new memory and configures itself accordingly. To test the newly installed memory, follow these steps:

1. When you switch on the power and see the "Testing System" message, press Command-Command-tilde (~). This brings up the system ROM monitor with the "NeXT>" prompt.

2. Type m to initiate an extended test of the computer's memory configuration. If your installation was successful, you'll see a list of the memory sockets and what's in them.

Here are some companies known to have NeXT memory:

Stratum Technologies 512/258-3570, 800/533-1744

NeXTConnection 603/446-7771, 800/800-6398

South Coast Electronics 714/669-9503, 800/289-8801

Third Wave Computing 512/832-8282, 800/284-0486

Memory International 714/588-0488, 800/266-0488

Clear Point Computers 508/435-2000, 800/253-2778

Sheecom Computers 714/637-4800, 800/366-4433

Chip Merchant 619/268-4774, 800/426-6375

Memory Plus 508/366-2240, 800/388-7587

Technology Works 512/794-8533, 800/688-7466

Impediment 617/837-8877

Micro Electronic Technologies 508/435-9057, 800/766-7466

Peripheral Outlet 405/332-6581, 800/332-6581

ETC 813/884-2863, 800/882-2863

Daniel Miles Kehoe is a contributing editor to NeXTWORLD.