Umax SuperMac S900

The SuperMac S900 (known as the Pulsar in Europe and Asia) was Umax’s first Mac clone and would remain Umax’s most powerful, most expandable computer and the last production Mac clone with 6 expansion slots until the S910 arrived.

Umax SuperMac S900The S900 in unique in that it has a second CPU slot, but only accepts a Umax SuperMac secondary processor card. You cannot use any other type of card in that slot, and the second CPU must match the speed of the first.

The primary CPU uses the same daughter card connector as Apple’s Power Macs of the same era, providing lots of processor upgrade option to the S900 owner.

Umax was the only clone maker to acquire a Mac OS 8 license from Apple, and the version 5 installer CDs shipped with Mac OS 8.


  • S900/150 (Pulsar 1500). 150 MHz CPU, 50 MHz bus
  • S900/180 (Pulsar 1800). 180 MHz CPU, 45 MHz bus
  • S900/180 DP (Pulsar 1800 DP). Two 180 MHz CPUs, 45 MHz bus
  • S900/200 (Pulsar 2000). 200 MHz 604e CPU, 50 MHz bus
  • S900/200 DP (Pulsar 2000 DP). Two 200 MHz CPUs, 50 MHz bus
  • S900/225 (Pulsar 2250). 225 MHz CPU, 45 MHz bus
  • S900/233 (Pulsar 233). 233 MHz CPU, 46.67 MHz bus
  • S900/240 (Pulsar 2400). 240 MHz CPU, 48 MHz bus
  • S900/250 (Pulsar 2500). 250 MHz CPU, 50 MHz bus
  • S900/250 DP (Pulsar 2500 DP). Two 250 MHz CPUs, 50 MHz bus
  • S900Base with G3. 250 MHz G3 processor bundled with system


  • S900/150 introduced 1996.05.06, discontinued 1997.02.01
  • S900/180 introduced 1996.08.01, discontinued 1997.07.01
  • S900/180 DP introduced 1996.10.02, discontinued 1997.02.01
  • S900/200 introduced 1996.08.07, discontinued 1998.08.31
  • S900/200 DP introduced 1996.11.18, discontinued 1997.08.01
  • S900/233 introduced 1997.03.17, discontinued 1998.08.31
  • S900/240 introduced 1997.01.07, discontinued 1997.03.01
  • S900/250, S900i/250, and S900/250 DP introduced 1997.03.17, discontinued 1998.08.31
  • S900Base with G3 introduced 1997.11.03, discontinued 1998.08.31
  • requires System 7.5.3 through 9.1
  • CPU: 180-250 MHz 604e, upgradable with standard daughter card
  • second CPU: ASPD slot for adding second CPU, allows for dual processing (see Second Processor for SuperMac S900/910 for more details)
  • bus: 45-50 MHz
  • RAM: 16-64 MB (16 MB on motherboard), expandable by an additional 1024 MB to 1040 MB total using 8 DIMM slots and 70ns 5 volt EDO or fast-page DRAM; memory can be interleaved
  • Video: ixMicro Twin Turbo Graphics Accelerator standard with 4-8 MB VRAM, resolutions to 1920×1080, 24-bit color to 1152 x 870 with 4 MB, to 1920×1080 with 8 MB
  • L2 cache: 512k
  • hard drive: 2 GB or 4 GB SCSI-2, Ultra SCSI, or RAID
  • CD-ROM: 6.7x (150 MHz), 8x (180-233 MHz), or 24x (250 MHz, G3)
  • Zip drive: optional
  • Internal and external Fast SCSI busses (upgradable to Ultra Wide SCSI-3 with E100 card)
  • ADB: 2 ports for keyboard and mouse
  • two miniDIN-8 GeoPorts on back of computer
  • DB-25 SCSI connector on back of computer with SCSI-1 support
  • PCI slots: 6
  • ethernet: built in, upgradable to 100Base-T with E100 card
  • size (HxWxD): 17.25″ x 7.0″ x 17.5″
  • weight: 28 lb.

Accelerators & Upgrades

Online Resources


  • The J700 and S900 have a PCI bridge chip controlling all PCI slots except the first two, which use the normal Apple chip. As a result, only cards that are PCI 2.1 compliant can be installed in slots 3-6 (3-4 for J700). Problematic cards are usually older SCSI cards, and, for some reason, ixMicro cards such as Ultimate Rez (but not the older ixMicro Twin Turbo cards). There are claims that even ixMicro-branded cards have slot preference, and in a multiple-card setup at least one has to be in slot 1 or 2, while the other can be in slot 4 or 5.
  • Newer Tech recommends against using EDO memory in the J700 and S900, because these models have “occasionally exhibited some problems when running with EDO memory. These problems tend to become more pronounced when updating your machine with a G3 card. . . . Therefore, we are recommending people to stick with FPM (Fast Page Memory) in these machines. If you are already running EDO memory without apparent problems, we certainly don’t mean to imply that you should be having problems, merely that you could have some.”
  • Umax suggests updating the J700 and S900 to version 2.0.2 of the Licensing Extension if you’re using Mac OS 8 or 8.1. <>
  • The version of FWB Hard Disk Toolkit that ships with most SuperMacs is not compatible with Mac OS 8 or later. You must use version 2.0.6 or later, available on the Umax software updates page. Be sure to install the new drivers on your hard drive before you run the OS 8 installer. Also, you must be sure that you do not update the driver on your hard drive during OS 8 installation. Using an older version of FWB HDT or the Apple driver on the SCSI drive that came with the SuperMac may so botch the hard drive structure that you will need to reformat it and reinstall everything. (As always, you should do a full backup before installing new drivers or updating your operating system.)
  • If your monitor is coming up green with extensions off or until the entire system is loaded, you can adjust the TwinTurbo card to change this behavior. Be sure the computer is off, disconnect the monitor, remove the cover, ground yourself by touching the power supply, the carefully remove the video card. Next to the video ports is a jumper marked JP4. Remove it from the two pins it’s on and move it to the other end (it must still be on the middle pin). Reinsert the card, connect your monitor, and do a quick boot with extensions off (hold down the shift key while starting). If it’s not green, shut down the computer, seal it up, and go back to work. If the green should persist, put the JP4 jumper back where it was. (According to Sync on Green Returns on Restart, the 8 MB card does not have a JP4 jumper.)

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