iMac G5 Developer Note

Discussion in 'General Mac Discussion' started by Sun Baked, Sep 9, 2004.

  1. Sun Baked macrumors G5

    Sun Baked

    Joined:
    May 19, 2002
  2. Chip NoVaMac macrumors G3

    Chip NoVaMac

    Joined:
    Dec 25, 2003
    Location:
    Northern Virginia
    #2
    Thanks for the link.

    Found this interesting:

    Can't wait till the XBench tests start hitting.
     
  3. crazzyeddie macrumors 68030

    crazzyeddie

    Joined:
    Dec 7, 2002
    Location:
    Florida, USA
    #3
    Since when has the Boot ROM been on the PCI bus?
     
  4. ToddW macrumors 6502a

    Joined:
    Feb 26, 2004
    #4
    Looks like the iMac G5 does have dual DDR. The iMac keeps getting better and better.
     
  5. Daveway macrumors 68040

    Daveway

    Joined:
    Jul 10, 2004
    Location:
    New Orleans / Lafayette, La
    #5
    Very ineteresting, where did you get it from?

    I'm like the other guy^^, since when has the boot rom been on a PCI bus??
    I didnt know firewire was on PNY, i thought it was on the PCI, o well, you learn something new everyday.


    Im glad i bought one!
     
  6. KeareB macrumors member

    Joined:
    Sep 16, 2003
    #6
    Performance on single vs. dual memory bus & latencies

    I ordered the iMac with 512KB and bought a 1GB stick from third party (assuming it is CL-3). Acted too quickly, perhaps.

    Also from the developer note: "The iMac G5 supports CAS latencies of 2, 2.5, 3, 4, and 5." Of course I don't think we yet we know what latency the RAM is as installed by Apple.

    I wonder:

    1. Speed increase in moving from single to dual memory bus.
    2. Speed increase in moving from CL-3 to 2.5 or 2.
     
  7. rdowns Suspended

    rdowns

    Joined:
    Jul 11, 2003
    #7
    OK, I'm clueless here. Seems like I would want two identical DIMMs installed. I order it with 1-512MB stick from Apple. What 512MB DIMM should I buy?
     
  8. KeareB macrumors member

    Joined:
    Sep 16, 2003
    #8
    I'm not sure we know. Crucial only offers CL-3 (but at a reasonable price). I would guess that with a 512KB CL-3, the iMac will run at dual bus / CL-3 speed.

    Kingston, which is the only memory site to date which is in tune with the single vs. dual memory bus issue, has much higher prices, as does Apple. I don't know if this means their RAM is CL-2.5 or CL-2. Nor do I know what any performance boost would be if you paid through the nose for matching CL-2 sticks vs. CL-3 sticks.

    If you are willing to spend money for CL-2 sticks to get whatever performance increase that would offer, you are probably starting to get into the territory where it just makes sense to get a dual tower - whose % performance boost would dwarf either the single/dual memory bus or the latency issues raised here.
     
  9. Sun Baked thread starter macrumors G5

    Sun Baked

    Joined:
    May 19, 2002
    #9
    Long, long, time -- almost as long as we've had PCI, and most likely part of the Open Firmware introduction.
     
  10. ToddW macrumors 6502a

    Joined:
    Feb 26, 2004
    #10
    Best thing I think would be to wait till it comes in and then open that mother up and see what kind of RAM is in there. My guess would be that the best performance you can get per dollar is 2*512MB of dual DDR. That will probably get more bang for your buck. The chipset seems to perform like that of the nforce 2, its memory bus works in a similar way.
     
  11. aafuss1 macrumors 68000

    aafuss1

    Joined:
    May 5, 2002
    Location:
    Gold Coast, Australia
    #11
    Shasta-I wonder why Apple named one of the ASIC's with that name.
    Also one bus seems to have dual bandwith-800mbps, like FireWire 800 or a P4 800FSB.
     
  12. aafuss1 macrumors 68000

    aafuss1

    Joined:
    May 5, 2002
    Location:
    Gold Coast, Australia
    #12
    The audio is reminisciant to me of Intel's High Definition Audio in some ways-but not as high quality :


    How well does it compare to Intel's High Definition Audio on the latest PC's ?
    'Audio
    The iMac G5 sound system supports analog recording and both digital and analog playback.

    The iMac G5 sound system features a “Combo Output Jack” that supports both analog Headphones Output and Digital Output connectivity. Since a single connector is provided to support both Headphones Output and Digital Output connectivity, support of the Headphones Output and Digital Output is mutually exclusive. Audio output port selection is automatic. When no device is inserted into the “Combo Output Jack”, Internal Speakers are selected. When an optical cable is connected to the “Combo Out” jack then the Digital Output is selected. When an analog device is connected to the “Combo Out” jack then the Headphones Output is selected. It is not possible to simultaneous select or use more than one output at a time. Encoded audio, such as AC3, can be streamed only to the digital audio output. A mute control for the current active output port can be accessed in the Output section of the Sound panel in the System Preferences.

    Digital playback features Sony / Philips Digital Interface (S/PDIF) when an optical cable is connected to the audio output combo jack. S/PDIF technology results in a clean audio signal with no added noise to or from the external audio device. The Digital Output supports both PCM and AC3 formats. Digital output encoding conforms to IEC 60958-3. The IEC 60958-3 category code encoding for non-encoded (i.e. PCM) audio formats indicates an Optical Laser – CD device. The IEC 60958-3 category code encoding for encoded (i.e. AC3) audio formats indicates an Optical Laser – DVD device.

    Under control of the system software, the sound circuitry digitally creates and records sounds. The iMac G5 can receive input only from one of two analog input sources which includes a built-in microphone and Line Input. Hardware input gain control is supported over a range of –4dB to +20dB. The input gain control can be accessed using the Audio Midi Setup application included in the “Applications/Utilities” folder.

    The sound circuitry and audio device drivers support audio data in multiple formats. Both digital and analog outputs support PCM audio at 16 and 24 bits with sample rates of 32.000 KHz, 44.100 KHz, 48.000 KHz, 64.000 KHz, 88.200 KHz and 96.000 KHz. In addition, the Digital Output also supports AC3 audio at 16 bits with sample rates of 32.000 KHz, 44.100 KHz, 48.000 KHz, 64.000 KHz, 88.200 KHz and 96.000 KHz.

    If audio data recorded on another computer at a sample rate not supported by the iMac G5 hardware is played on the iMac G5, the Core Audio (Mac OS X’s OS Level Audio API) transparently sample rate converts the data to the current sample rate that has been selected on the iMac G5. To maximize audio fidelity, the Core Audio samples are stored as 32-bit floating point. The Sound Manager exists as a Carbon compatibility layer, but developers are encouraged to move their applications to Core Audio for maximum performance and fidelity, because the Sound Manager is not capable of supporting bit depths greater than 16 bits or sample rates greater than 48.000 KHz. Sample rates of 64.000 KHz, 88.200 KHz and 96.000 KHz are not supported by the Sound Manager. Bit depths of 24 bits are not supported by the Sound Manager.

    For more information about audio APIs on Mac OS X, visit the Apple audio technologies developer web page at

    http://developer.apple.com/audio/

    In this section:
    Digital Audio Output
    Audio Line Input Specifications
    Headphone Output Specifications

    Digital Audio Output
    Digital audio data is transmitted from the iMac G5 using an optical cable, commonly referred to as a TOSLink cable. The digital audio output format conforms to IEC60874-17.

    The audio output connector on the iMac G5 is a 3.5mm electrical/optical combination (“combo”) jack. The combo jack accepts standard electrical audio cables with a 3.5 mm stereo plug, and standard TOSLink optical cables that have a 3.5 mm optical plug. Typically, TOSLink optical cables are available with standard friction-lock ktype F05 plugs on each end. Adapters are available that attach to the F-05 plug and convert it to a 3.5 mm optical plug. TOSLink cables are available from pro-audio, musician’s supply, hi-fi and other retailers.

    For details on the S/PDIF digital output format and performance specifications, refer to “Digital Audio Output Specifications”.

    Digital Audio Output Specifications
    During playback of a 1KHz, full-scale sine wave (S/PDIF output format, 44.1KHz output sample rate, 24-bit sample depth, unless otherwise specified) the digital audio output has the following nominal specifications:

    Jack Type: 3.5mm Analog/Optical Combo Jack



    Output Data Formats: S/PDIF (IEC60958-3), AC3



    Output Sample Rates: 32KHz, 44.1KHz, 48KHz, 64KHz, 88.2KHz, 96KHz



    Bits per Sample: 16 or 24 (S/PDIF),16 (AC3)



    Frequency Response: 20Hz – 20KHz, +/-0dB



    Signal-to-Noise Ratio (SNR): >130dB



    Total Harmonic Distortion + Noise (THD+N): <-130dB (0.00003%)



    Channel Separation: >130dB



    Audio Line Input Specifications
    The iMac G5 has a stereo audio line input jack on the back panel. The audio input is designed to accept audio signals with input levels ranging from 150mVRMS (-14.3dBu) to 3VRMS (+11.8dBu). The input gain should be set according to the input level so as not to clip the input to the A/D converter in the CODEC. Input gain control is supported over a range of –4dB to +20dB. The input gain control can be accessed using the Audio Midi Setup application included in the “Applications/Utilities” folder. The default input gain setting is 0dB, which will accommodate an input level of 2VRMS (+8.2dBu), which is the typical output level from CD players, DVD players and other consumer audio equipment. With an input gain setting of 20dB, the minimum recommended input level is 150mVRMS (-14.3dBu), which will correspond to 3dB below full-scale on the A/D converter in the CODEC.

    The audio input jack is a 3.5 mm miniature phone jack with the signals connected as follows:


    Tip
    Left-channel audio

    Ring
    Right-channel audio

    Sleeve
    Audio ground



    During input of a 1KHz, full-scale sine wave (44.1KHz input sample rate, 24-bit sample depth, unless otherwise specified) the audio line input has the following nominal specifications:

    Jack Type: 3.5mm Analog Jack



    Input Sample Rates: 32KHz, 44.1KHz, 48KHz, 64KHz, 88.2KHz, 96KHz



    Bits per Sample: 16 or 24



    Input Impedance: > 20K Ohms



    Input Gain Range: -4dB to +20dB



    Typical Input Level (Input Gain = 0dB): 2VRMS (+8.2 dBu)



    Maximum Input Level (Input Gain = -4dB): 3VRMS (+11.8dBu)



    Minimum Input Level to Achieve Full Scale on A/D (Input Gain = 20dB): 200mVRMS (-11.8dBu)



    Minimum Recommended Input Level (Input Gain = 20dB): 150mVRMS (-14.3dBu)



    Frequency Response: 20Hz – 20KHz, +/-0.5dB



    Signal-to-Noise Ratio (SNR): >90dB



    Total Harmonic Distortion + Noise (THD+N): <-85dB (0.006%)



    Channel Separation: > 85dB



    Headphone Output Specifications
    The iMac G5 has a stereo audio output jack on the back of the enclosure. The audio headphones output is suitable for connecting amplified external speakers, audio equipment, or headphones.

    The audio output connector on the iMac G5 is a 3.5 mm electrical/optical combination (“combo”) jack with the electrical signals connected as follows:


    Tip
    Left-channel audio

    Ring
    Right-channel audio

    Sleeve
    Audio ground



    Note: : For best results, equipment plugged into the headphones jack should not connect the audio ground to other grounds, such as the chassis or “green-wire” ground.

    During playback of a 1KHz, full-scale sine wave (44.1KHz output sample rate, 24-bit sample depth, 100K ohm load, unless otherwise specified) the audio line output has the following nominal specifications:

    Jack Type: 3.5mm Analog/Optical Combo Jack



    Output Sample Rates: 32KHz, 44.1KHz, 48KHz, 64KHz, 88.2KHz, 96KHz



    Bits per Sample: 16 or 24



    Output Impedance: <50 Ohms



    Output Level: 1.75VRMS (+7.1 dBu)



    Frequency Response: 20Hz – 20KHz, +/-0.5dB



    Signal-to-Noise Ratio (SNR): >90dB



    Total Harmonic Distortion + Noise (THD+N): <-85dB (0.006%)



    Channel Separation: >85dB



    Output Power (Into 16 ohm Headphones): 60mW'-from G5 iMac dev note.

    So:
    -supports dual outputs
    -upto about 100KHz output sample pass
    -S/PDIF output
     
  13. aafuss1 macrumors 68000

    aafuss1

    Joined:
    May 5, 2002
    Location:
    Gold Coast, Australia
    #13
  14. sjk macrumors 6502a

    Joined:
    May 2, 2003
    Location:
    Eugene
    #14
    I'd check with transintl.com. When I bought a 1GB DIMM for my eMac they told me it used the same Samsung chips as Apple RAM, tho' I forgot to check it before I installed it. And they're less expensive than over-hyped Crucial. :)
     
  15. tateusmaximus macrumors member

    tateusmaximus

    Joined:
    Sep 9, 2004
    Location:
    sydney
    #15
    do you think there would be any advantage in going higher than ddr400? like ddr533 (still ddr not ddr2). i dont know how these memory controllers work in macs!

    seems like dual channel is the way to go either way.
     

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