Facts and rumors around the PowerMac G4 with UMA 2 architecture (Core99)

Well, as you know the new UMA 2 PowerMac has been released at MWSF 2001. Not all my predictions were correct (of course), so I'd like to compare the Plausible version with the actual version that will be available in February.

These tables below show 3 versions of the UMA 2 PowerMac, also known by the name "Shark", which is actually part of the bridge chip system on the UMA 2 motherboards, and not the codename of the machine.

Table nr.1 show the thing that actually was released, nr.2 shows a version that I though was very plausible, nr.3 has some more unconfirmed rumors in it and nr. 4 even adds a few rumors. I'd say nr.3 and nr.4 are more like the machines that are going to surface at MWNY or later this year. All the important specs will be looked at more closely afterwards. For questions and comments, you can contact me at bensch@g-news.ch.

Last updated on: 01/11/2001


The UMA 2 PowerMac compared with the rumors, and a new version added
Part: Actual (true) Plausible (old) Possible (old) Unlikely (old) MWNY updated version (rumor)

466-533 MHz G4 (MPC7410) and 667-733MHz G4e (MPC7450)
all single, 533 avail. in 2x

600-733MHz single or dual G4e (MPC7450) Dual or quad 600-900MHz G4e (MPC7450) Single or MP 1GHz+ G4e, Apollo, SOI

Single 800MHz -1GHz G4e (MPC7450) or Apollo (with SOI)
Dual or quad versions at lower speeds also

Cache: 1MB L2 2:1 or 256KB L2 1:1 and 1MB L3 3:1 256KB L2 1:1 256KB L2 1:1, 1MB L3 2:1 256KB L2 1:1, 2MB L3 1:1 256KB L2 1:1, 1MB L3 3:1 or slower
Bus: 133MHZ MaxBus 133MHz MaxBus 133MHz MaxBus @ 128bit 133MHz+ MaxBus @ 128bit 133MHz+ MaxBus
AGP: 4x AGP (266MHz) with write combining, 3 RAM slots 4x AGP (266MHz), 4 RAM slots 4x AGP Pro(266MHz), 4 RAMslots Dual 4x AGP Pro(266MHz), 8-12 RAM slots 4x AGP or AGP Pro, write combining, 4 RAM slots
PCI: 4x 33MHz, 64bit 3x 33MHz, 64bit 3x 33MHz, 64bit & 3x 66MHz, 32bit 6x PCI-X 4x 33MHz, 64bit
HDD: ATA 66 controller w/2 ports ATA 100 controller w/ 2 ports ATA 100 controller w/ 2 ports ATA 100 & UW320 in PCI, hot swappable, native FireWire drives ATA 100
DVD: CD-RW or SuperDrive 10x Speed 12x Speed 16x Speed / DVD-RAM SuperDrive in all models except the smallest
Graphics: Rage 128 Pro or nVidia GeForce2 MX 32MB SDR ATI RADEON AGP 4x RADEON or NV20 AGP 4x RADEON Pro or NV20 AGP 4x nVidia GeForce2 MX in all models, Geforce 3 in the top models or as BTO
Sound: 16bit onboard with 10W amplifier 16bit onboard & 128bit PCI 128bit PCI only 128bit onboard 16bit onboard with 10W amplifier, SoundBlaster LIVE! as BTO
Networking: 10/100/1000BaseT & Airport (opt.) 10/100/1000 BaseT & Airport (opt.) 10/100/1000 BaseT, Airport (opt.) and FireWire 10/100/1000 BaseT, Airport and FireWire 10/100/1000BaseT & Airport (opt.)
USB: 2 SUB ports (separate) 2 USB ports (separate) 4 USB ports (spread over 2 buses) 2 USB 2.0 ports (480Mbit) 2 USB 2.0 ports (480Mbit)
FireWire: 2 ext, 400Mbit 2 ext., 1 int. 400Mbit 2 ext., 1 int. 800Mbit 2 ext., 2 int. 1600Mbit 2 ext, 1 int. 800Mbit
Removable: Zip 250 drive IDE (opt.) Zip 100 (IDE) Zip 250 (IDE) Zip 250, int. FireWire Zip 250 (IDE) opt.
Input: Fullsize Pro Keyboard, one button optical Pro mouse Full sized Keyboard, 2 button Wheelmouse, optical Full sized Keyboard, 3 button Wheelmouse, optical Full sized Keyboard, Optical multi-button mouse Fullsize keyboard, wireless?
Optical 2+ button mouse
Case: Graphite Mini Tower Graphite Mini Tower Bigger, more drive bays Huge Bigger, more drive bays (also external ones)
Other: 56K V.90 Modem (in slot, I guess) Modem slot Modem slot Modem slot 56K V.90 Modem in slot


G4e indepth:

  • 0.18 first, later 0.15-0.13 micron process in copper
  • 256K on-die level 2 cache at 1:1 ratio
  • possible level 3 cache off-die up to 2MB
  • up to 733MHz initial speed
  • 256bit CPU to cache bus (up from 64bit)
  • support for up to 64GB of physical memory (up from 4GB), due to 36bit addressing mode
  • enhanced MaxBus performance (64 and 128bit modes)
  • enhanced use of the Altivec units and improved execution unit performance
  • 32bit architecture
  • longer pipelines, 7 stages (up from 4), to allow for faster operation clockspeeds
  • 1.5Volts consuming an average of about 10W (lower, think PowerBook G4)
  • SOI (Silicon on Insulator) to be used in G4 gen. 4 (codename Apollo), will further enhance performance and lower power consumption and requirements
  • See this PDF file for more info (very interesting, really)



  • 100-166MHz bus doubled by DDR (Double Data Rate) to 200-333MHz performance
  • 2664MB/sec maximum throughput (PC100 SDRAM has 800MB/sec)
  • Much cheaper than RDRAM (faster too in most cases)
  • Very fast



  • 4x AGP supports up to 1024 MB/sec throughput, offers support for 1x and 2x AGP cards
  • AGP Pro is a slightly enhanced version of AGP 4x, offering extra connectors, however this is not even being used on PCs yet
  • PCI-X is the successor to current PCI, unlikely to appear before the very end of 2000, new standard, 1064 MB/sec max. (up from 256MB/sec) (2001 now and still now PCI-X)
  • ATA 100 is simply faster than ATA 66 (however dubbed to be about 50% faster than ATA 66)
  • FireWire can run at 800+Mbit/sec, but Apple has problems finding a supplier for those controllers.
  • 10/100/1000 BaseT controllers exist already and are being used in current G4s
  • ECC RAM is unlikely to make it to the Mac
  • VBS (Virtual Buffer System) is a pretty complicated technology adding some kind of buffer to RAM to make it even faster (I understand this as some kind of pipelining the RAM)
  • L3 is being used in the upcoming G4 Towers with the MPC7450 chip.
  • Graphics: The low end machines stick to Rage 128 Pro at the moment, which may be replaced by Radeon some time in the future, the high end machines have nVidia GeForce2 MX cards, which are likely to be replaced with the NV20 card once it's ready.

The overall performance of these new UMA 2 PowerMacs can be somewhere between 50-200% faster than
current G4 Sawtooth systems. What remains clear is that they're going to be a major step in the history of the
PowerMac. I expect the first systems based around UMA-2 around MWSF 2001 in January. (and I was damn right)

Thank you for your interest,

Bensch Blaser

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© Bensch Blaser, 2000