The Twentieth Anniversary Macintosh is sold as a pretty complete package, but there are a few things you can do to upgrade the machine. One issue when upgrading a machine like this is appearance, as you don't want to take a machine as elegant as the Twentieth Anniversary Macintosh and slap on an ugly hard drive, printer, trackball etc. and create an unsightly mess next to your Macintosh.
The Twentieth Anniversary Macintosh has two dimm slots, each capable of holding a 64MB dimm for a total of 128MB of RAM. You must use 5 volt 64-bit 168 pin 60 nanosecond EDO (or FPM) dimms with a 1k or 2k refresh for this machine. The 1k/2k refresh is essential as your machine will not work with 4k refresh chips. This machine will not accept more than 128MB of RAM.
The Chip Merchant carries memory for this machine and generally has the best prices around. They no longer carry the EDO variety, so you will have to settle for the fast page memory, which is a little slower. Other World Computing still sells the EDO variety as of this writing.
Connectix makes Speed Doubler 8, which does several things for this machine. It provides faster emulation of 680x0 code, which can speed certain system functions and older software, it provides faster finder and network copying, and it provides faster disk access. The faster disk access alone makes this product worth the $65 or so. Be sure to upgrade to version 8.1.2 from their website if you use Mac OS 8.1 or greater. Later OS revisions seem to have made Speed Doubler less important, but if you're looking for every last edge, this is one worth considering.
Unfortunately, this product is no longer sold and is not compatible with Mac OS 9. If you are going to run an older system, such as 7.6.1, 8.1 or 8.6, you might try ebay to pick this up.
After installing a 1 Meg level two cache in my machine the MacBench score jumped from 361 to 438! That's almost a 20% improvement in processor speed. The logic board of the Twentieth Anniversary Macintosh is based on the 6500 series, so a cache that works in the 6500 will work fine. Beware that cache for the 7500 and 8500 series macs will not work in this machine. The cache model that I ordered was listed for the 6400, and it works great. Finding one of these will be very difficult these days.
There have been bad batches of 1MB level 2 cache chips out there, so be careful when you buy one and be sure that whoever you buy it from doesn't hit you with a restocking fee if you return it. Also, a word about price. There are vendors charging up to $279 for this item, when it is available for as little as $140 if you shop around. Please, don't reward vendors who want to take you to the cleaners.
Do NOT buy this item if you are plan to purchase a G3 upgrade soon, as the G3 upgrade will replace your Level 2 Cache.
What was formerly thought impossible has happened: There are G3 upgrades for the Twentieth Anniversary Macintosh. Several vendors offer these including Sonnet Technologies, who seems to have the best solution out there right now. Keep in mind that most upgrades require the fat back and at least the early ones blocked one of the RAM slots. Sonnet has announced a 500 Mhz G3 upgrade for the Spartacus, by FAR the fastest upgrade you can get for your machine.
The Twentieth Anniversary Macintosh uses a 2GB IDE powerbook size drive. Mac Components Engineered sells several drives that will work in this machine. Any IDE drive that runs in a powerpc powerbook should work. I am aware of several people who have done this, and it's a fantastic upgrade. Be sure you tell MCE that you are using a 20th Anniversary Mac, as they have the correct bracket. Also, some folks have experienced problems with certain IBM 5GB drives, and MCE knows which ones work and which ones don't. Internal powerbook-type drives are expensive, but that's the price you pay for elegance. If elegance is not an issue (and if it isn't, why did you buy this mac?), any external scsi drive from APS will work quite well, and provide more storage for the money.
There is an issue with the mounting brackets and the twentieth anniversary mac. The older drives use a bracket with 38mm spacing, and the newer drives use a 76mm spacing. MCE should be able to sell you a new bracket. I believe they may even sell you a bracket alone if you purchase a drive somewhere else, although their knowledge of the 20th Anniversary Mac makes them the vendor of choice in this area.
If you are like me, the fondle-pad gets tiring on the hand for extended periods of use. A company called CoStar used to make a trackball called the Stingray that comes in black, and looks good with the Twentieth Anniversary Mac. I've found that this is not nearly so fatiguing on the hand over long periods of use. On the other hand, it's not nearly as comfortable as the Kensington Turbo Mouse, but it looks 1000 times better.
Another option is to order a granite colored mouse from an Apple service provider. The part number for the granite ADB mouse is 922-2328. A granite Apple keyboard is part number 922-2327 if you want a matching set. Another option is to order ADB accessories for the old NeXT computers, which were jet black. Turbo Software carries these products.
If you have an ethernet network you can connect to your machine, installing an ethernet card in the communications slot will provide a dramatic speed increase for all network activity. The twentieth anniversary mac uses as Communications Slot II which is pci-based. It is NOT a full pci slot, and it is NOT a Communications Slot like they put in the old LC's.
There are scsi-port ethernet adaptors out there, but they are slower, not too reliable, and may not work with OS 8.5. If you come upon one really cheap, go for it, otherwise the comm slot is your only option. I have heard reports of people having trouble with these, and Asante states that their scsi-ethernet solution is not supported on any powermac.
The Geoport Telecom Adapter II is really neat and provides some cool CTI features, but it is definately not a very fast modem. While rated at 33.6kbps it rarely actually provides that kind of throughput. Purchasing a 56k modem will make your web surfing a much better experience. Be sure to look for one that conforms to the V.90 56k standard. If you can swing the expense, ADSL will make a HUGE difference, but will require an ethernet card. The Global Village modems look good, can be spray painted a similar color as your Twentieth Anniversary Macintosh, and provide elegant software for sending and receiving faxes. I personally purchased a Global Village 33.6+Voice which came in a nice powerbook gray, and it seems much faster than using the Geoport Pod.
Another option is a cable modem, available in more and more areas. These connect to your computer through an ethernet card, and provide 1.5Mbs as opposed to 56kps, by far your fastest option (this or ADSL). In many cases the cable company will provide the ethernet card, so don't rush out and spend your money on one until you find out.
You cannot plug in a separate monitor to the Twentieth Anniversary Macintosh without installing a separate video card in the 7" PCI slot.
You cannot install a 3D graphics card that requires you to patch through the video. 3dfx based voodoo cards are a noteable example. The new voodoo3 might work, but I haven't yet received confirmation of someone using these with a twentieth. Either way, you will have to use them in conjunction with an external monitor.
You cannot use an Apple DOS card that requires you to patch into your computers video connection.
You cannot install a PCI card that is larger than 7" into the case.