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.
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.
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.
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.
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
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.