ActionMOOD@aol.com
Fri, 25 Jun 1999 16:27:19 EDT
Currently firewire supports 400Mbits/sec (25MBytes/sec) with future limits
pushing 1.5Gbits/sec (~200MBytes/sec). Current DV cameras I've used are
pumping out only 3.6 MBytes/sec. The video recorded on the tape is recorded
compressed at the DV data rate for compressed video.
SCSI comes in a many of flavors.
SCSI-1 max 5MB/s.
I'm pretty sure the internal bay on the 8500 was 10 MByte/sec (SCSI 2 aka
fast-narrow).
SCSI-2 Fast+wide got you 20 MB/s. (This is what I use with a Radius VVS on
Quadras and routinely capture at 3-5 MBytes sustained with VVS M-JPEG
compression).
I can never keep the next levels straight beacause it seems that SCSI-3 and
Ultra stand for 40 MB/s and the SCSI-3 LVD can pump out 80 MB/s.
Now the bus. Apple's SCSI manager 4.3 allowed for bus mastering between
peripheral cards plugged into slots on the motherboard. This allowed for
companies like ATTO and FWB to communicate with Radius and Targa hardware at
the highest possible data rate that the bus itself could support. In Quadras
and early PCI MACs the bus supported between 33 and 66 MHz. In fact the
Yosemite Macs also have a 66MHz Peripheral Interconnect (PCI) bus. You
should not confuse this with the advertised 100 MHz system bus. The 100 MHz
system bus is for the bus between the G3 processor and main memory versus.
The 66 MHz bus speed is between processor and peripherals. If you assume
bus mastering could pump one byte from a DV interface down the PCI bus and
through a SCSI interface for each clock cycle then you might achieve 66
MByte/sec transfers. The acual limit is less but I hope I havent gone to
far. Did I forget to mention bus transaction overhead?
Botom line. The DODV (Radius) firewire card has had the least bad press as
far as I can tell. The Adaptec 8945 (SCSI+Firewire) card reviews I've read
have not looked that good. We capture to Wintel NT boxes using FASTs
DV-master set up (arrgghhh). G4 macs are in out purchase plan. Come on
Apple!
-sam
This archive was generated by hypermail 2.0b3 on Fri Jun 25 1999 - 19:42:44 PDT