Last week I introduced
myself and spoke of how I would try to help others get Linux
running on their low-end Macs. This week we'll look at what
hardware is needed and which hardware will make for a faster
running system. Keep in mind that some of this may appear to be
intimidating, but doing your homework now will hopefully avert
problems later on.
Minimum Recommended Hardware
I recommended certain types of Macs last week, and I will expand
upon that now. I don't recommend installing on Linux NuBus Macs
mainly due to lack of support - some things work and some just
don't. I intend to focus on the Old World PCI-based Macs, which are
well supported but need more preparation to get Linux up and
running properly than the New World machines.
Processor: 603s and 604s are adequate, but a G3 or G4
will give much better performance due to the faster, larger,
integrated backside Level 2 (L2) cache. Faster isn't always better
- having more memory will give you a more noticeable speedup than a
faster processor with too little RAM. Running a G4/800 with 64 MB
RAM will be no faster than a G3/400 with 512 MB RAM, if not
slower.
Linux programs can make use of the AltiVec "velocity engine" of
the G4, but it's not a necessity. Further, I have seen some issues
with getting the G4's L2 cache working correctly on Old World
machines. Good speed G3s can be found on eBay for around
$25-100 depending on your machine. G4s usually carry a hefty
premium that doesn't always show the best return.
Memory: 128 MB is a good start; 256 MB or more is better.
I have installed a modern Linux with just 80 MB RAM on a Power Mac 7500, but it was really
slow.
512 MB would be excellent, and I don't really recommend any more
than that. With 256 MB RAM, I still have over half of that free or
being used by Linux as disk cache, so unless you're running
OpenOffice and the GIMP at the same time, you don't need to go
crazy.
Also keep in mind that the 4-digit Macs used Fast Page Mode
(FPM) memory. Some also accept EDO (Extended Data Out) memory and
use it like FPM. FPM memory has different notches than the newer
SDRAM used since the Beige G3s,
and they won't interchange. Most PCI machines support interleaving
memory (using slot A1 and the B1 instead of A1 and A2), which can
give about a 20% speed boost.
Hard Drive: The stock MESH (Macintosh Enhanced SCSI
Hardware) controller on the Old World Macs is abysmally slow. It's
only a 5 MB/s controller. The NCR controller was slightly better,
at 10 MB/s, but most of the Macs I have come across have the drives
connected to the slower MESH controller.
The onboard controllers are fully supported, but I recommend a
PCI SCSI card. Adaptec's
2940 series are very fast (up to 80 MB/s), show a large
improvement in speed over the stock cards, and are available on
eBay for around $10.
A PCI IDE controller can be a good choice as well, and all the
newer IDE drives are much faster than the old SCSI drives anyway.
Further, the CD-ROM drive can be connected to the NCR or MESH
controller to allow the hard drive to run at full speed on the
faster controller.
The newest option is PCI SATA controllers, which should work
without a hitch on PCI Power Macs, clones, and beige G3s. More on
that after some testing.
Video Card: Linux supports ATI Mach64 based cards, like
the Rage IIs, the Rage LTs, etc. They will work fine, and some Macs
have these onboard, like the Beige G3 and the WallStreet PowerBooks. For those who
can get one, a Rage 128 or a Radeon 7000 would be a better choice
on the higher end, and are also available on eBay for around
$10-30.
Some Macs came with the ixMicro Twin Turbo card (such as the
Power Mac 9600). While this is a
decent video card, there is very little support for it. I have
managed to get them to run under X-Windows, but not well, and when
I tried to adjust the settings, I lost the ability to run
X-Windows. For this reason, I don't recommend it.
Other PCI Macs, like the 7500, have an onboard frame buffer
device that will work under Linux and X-Windows, but it won't be
very fast. A low-end ATI video card will be faster. Further, you
can do a dual head display under X-Windows using the onboard video
along with a PCI video card.
Note about ATI under Linux: There is a bug in the Linux driver
for the ATI cards under text mode that causes there to be several
vertical lines that are fuzzy and hard to read. This bug does not
affect using the GUI under X-Windows, only text-mode.
Preparation: This is the key to a smooth install.
Inventory what your system has and what it may need, as well as
what you can do to make it better. A useful tool is the Apple
System Profiler (under the Apple menu). This will give you lots of
info about your Mac. Newer versions of the Mac OS will show more
information, but you should be able to get what you need from any
version newer than 7.x.
Under the System Profile tab:
- Memory overview: Shows built-in memory and L2 cache, if
available. Ignore the Virtual memory info. (Linux handles virtual
memory differently from Mac OS and WinDoZe)
- Processor info: Listed under Hardware Overview in v9.2.2. This
shows your processor type and machine speed.
Devices and Volumes tab:
- Under this tab, you will find info on your hard drives, video
cards, CD/DVD drives, etc. You will have to click on the arrows to
expand the fields to get all the info. If you have a non-Open
Firmware PCI card installed, it will not give much information on
it, but don't worry, Linux will be able to make use of it. The only
PCI card that I never got working on a Mac under Linux was a
Via-based USB card.
Summary
- Processor: 603 or 604s are good. G3s are great. G4s
work, but may require extra steps to get the L2 backside cache to
work properly (I will delve into this more when I can).
- Memory: 128 MB to 256 MB RAM. No more than 512 MB really
needed.
- Video: ATI Rage series. ATI Rage 128 or Radeon
recommended. ixMicro not recommended. Onboard video works, but can
be slow. Primary display has to have an Open Firmware
BIOS.
- Hard Drive and Controller: PCI-based SCSI or IDE
controller connected to a newer drive will give best results.
Otherwise, connect the hard drive to the NCR controller and the
CD-ROM to the MESH controller. The PCI card does not have to have
an Open Firmware BIOS. I recommend that Linux be installed on a
drive separate from Mac OS if at all possible to make this as easy
as possible.
- OS X and the 8 GB limit: Those of you you have installed
OS X on a low-end Mac have probably run into the 8 GB
limit. Linux does not have this problem and will successfully
install onto any size drive. Further, I have successfully installed
Linux on a Beige G3 with a Rev A ROM on a slave drive with no
problems. OS X requires a Rev B or C ROM to be able to see the
slave drives.
Hopefully I haven't scared you away with all this "geek" speak.
It's probably more than what some Mac users may have ever dealt
with, but having all this info ready will make the install that
much easier. Of course, some of you guys may know more about this
than I do.... Next time I will discuss how to acquire the BootX
Linux boot program and how to set up your hard drives for Linux,
and to get ready to start the installation. 
