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iMac
G3/G4 Q & A:
Technical & Performance (3/3)
Are third-party processor upgrade
cards available?
Newer Technology, PowerLogix, and Sonnet Technologies have designed upgrade cards for early models of the iMac that circumvent the ROM-issue. Basically, each company has installed a faster processor on an iMac daughtercard with an original iMac ROM.
Newer Technology filed for bankruptcy on December 28, 2000, but PowerLogix and Sonnet continue to offer iMac upgrades. For additional information on these particular cards, be sure to check out the Upgrade Cards: By Compatible System: iMac listing on EveryMac.com.
Will third-party video cards, TV cards, or 3DFX cards be available?
It is theoretically possible that third-party vendors will utilize the "Mezzanine" in revision A & B iMacs to create various cards, but since the slot was removed in the iMac "266" and later iMac models, it is no longer likely. As for a 3DFX card, MicroConversions created a 3DFX, Voodoo 2 card for the iMac that accelerated all 3DFX-enabled games. Unfortunately, when the "Mezzanine" slot was removed in the "266" iMac, Microconversions ceased operations.
The iMac is not purely CHRP-based, but work previously done on the CHRP/PPCP architecture did benefit the development of the iMac. The iMac includes OpenFirmware and USB which were both elements of CHRP. Keeping costs low were also a high priority of CHRP design, which was also a high priority in the development of the iMac.
The iMac does not have the traditional 4 MB ROM that the original "Beige" Power Macintosh G3 series has, but it does have a Boot ROM that is around 1 MB. The Boot ROM contains software to initialize the computer, OpenFirmware, the MacOS ROM image, and device drivers. The remaining 3 MB of ROM is loaded into RAM by OpenFirmware. The result of the ROM being loaded into RAM is that many instructions are executed more quickly, making the iMac slightly faster, but 3 MB of RAM cannot be used by the system or applications.
Is the iMac a Network Computer (NC)?
Not in the traditional sense that it requires a network to operate, but it does have fast 10/100Base-TX Ethernet built-in for high speed networking, as well as OpenFirmware that makes true "network booting" a reality. The iMac is able to boot from a MacOS X-based server.
How much RAM can the iMac support? How do I install it?
Officially, the original iMac series can support 128 MB of RAM with two 64 MB 10 ns SO-DIMMs. Both SO-DIMMs used in the iMac must use SDRAM, not EDO or SGRAM (with a "G"). One RAM slot is located on top of the daughtercard and can accommodate RAM that is up to 2.0 inches high, and the other slot is located on the bottom of the daughtercard and can accommodate RAM that is 1.5 inches high. Unofficially, the iMac can support up to 384 MB of RAM, using one 2.0-inch 256 MB SO-DIMM, and one 1.5-inch 128 MB SO-DIMM. It also should be noted that only the top slot is intended by Apple to be user-upgraded.
When announced, the "Kihei" iMac series was said to support 512 MB of RAM by using two 256 MB, non-interleaved 168-pin, 64-bit-wide, 8 ns PC100 SDRAM DIMMs. However, the "Kihei" iMac series can support additional RAM by using two 512 MB DIMMs, for a total capacity of 1.0 GB.
The "Indigo", "Flower Power", and "Summer 2001" iMac families can support up-to 1.0 GB of RAM by using two 512 MB, non-interleaved 168-pin, 64-bit-wide, 8 ns PC100 SDRAM DIMMs, the same type as the "Kihei" series. In the future, however, these iMacs may be able to support additional RAM with higher-density DIMMs.
The "Flat-Panel" iMac models can support up-to 1.0 GB of RAM total (or 768 MB of RAM without "intervention by an Authorized Apple Service Technician"), by using one 512 MB, non-interleaved 168-pin, 64-bit-wide 8ns PC133 SDRAM DIMM (one 512 MB 184-pin PC2700 333 MHz DDR SDRAM DIMM after September 8, 2003). The "Flat-Panel" iMacs have two RAM slots, one that ships pre-installed with either 128 MB or 256 MB of RAM and is not intended to be user-upgraded, and one open SO-DIMM slot that can easily be upgraded by the user.
Does the iMac support external monitors? Dual monitors?
If the back of the orginal iMac series is removed, it can power an external monitor by disabling the internal monitor and driving the display on the external monitor. However, the original iMac series was not designed to support external monitors or dual monitors. "USB monitors" simply plug into the standard Apple video port on "traditional" Macs and have a USB hub built-into the monitor. Unfortunately, these monitors cannot be hooked up to the orginal iMac series via USB ports.
Unlike early models in the iMac series, according to Apple-published documents, the "Kihei", "Indigo", "Flower Power", "Summer 2001", and "Flat-Panel" iMacs all support "video mirroring" on an external monitor up-to 20".
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