At 10:25 -0600 12/06/2002, Andy Ball wrote:
>Hello!
>
>I'm trying to help out a friend who recently picked up a
>300MHz beige G3 Mac.  He says the mainboard supports both
>SCSI and ATA disk drives.  I've trawled my usual sources
>(LEM, google etc.) without finding much in the way of
>specifics.

>He's thinking of upgrading its disk drive.  I've read that
>it supports "wide SCSI", but I'm not sure if this means
>single-ended, hvd or lvd (I'm guessing single-ended).  I'm
>also wondering about the speed of the SCSI bus (20MHz?)

The built-in SCSI in the Beige G3 is unenhanced narrow SE SCSI-II. 
5 MB/s theoretical.  It's good for hooking up peripherals like 
CDROMs, tape drives, scanners and removable media drives, but not 
much good for fast storage.  There are folks who will tell you that 
it is 10 MB/s but they are confused because they believe that SCSI-II 
is synonomous with Fast SCSI-II.   The Beige SCSI is unenhanced, not 
Fast.

IIRC, the built-in ATA is ATA-33 (or is it 16?) which isn't the 
fastest around, but only the newer hard drives deliver sustained 
performance better than 33 MB/s anyway, so it should be adequate 
unless he's really hard core about performance.  Hmmm.  Apple's 
Developer Note says that it supports ATA-2.  Is that 33 or 16 MB/s?

Some G3s shipped with an optional SCSI card installed.    If his is 
one of those, it should be obvious, because there will be an Adaptec 
or Atto brand SCSI card in one of the three PCI slots.   You'll need 
to identify the SCSI card to determine (or ask) what SCSI protocol it 
supports.

>Does his beige G3 support 5V cards, 3.3V or both? As
>you can tell, I'm not all that familiar with this model.

The Beige G3 PCI slots supply both 5V and 3.3V but the 5V signaling 
standard must be used.   In other words, if you need a 3.3V supply on 
the PCI card, it's available, but by the time the signals leave the 
card, they need to be 5V signals.   The slots are 32 bit, 33.3333 
MHz.

If he still has a copy of the Mac OS installed, launch the Apple 
System Profiler from the Apple menu and scroll down to "ROM 
Revision".  If he has $77D.40F2 then he has a Rev. A ROM and slave 
drives are not supported on the IDE busses.  If he has a later 
revision then slave drives are supported.    If you doesn't have 
Apple System Profiler or a similar utility available, you can pull 
the ROM module and read the numbers off of the chips.   If the two 
chips read 341S0402  and 341S0403, then he has the Rev. A ROM.

Jeff Walther