Re: What G3/G4 accelerator cards work with PowerPC Linux?
On 25 Oct, this message from Peter Canning echoed through cyberspace:
> I have a PowerMac 7300 (200 MHz 604e) and I'm thinking of using my tax
> rebate to purchase an accelerator card. The cards I'm aware of are Sonnet
> Crescendo, PowerLogix PowerForce, XLR8 Carrier, and XLR8 MACh Carrier.
>
> Can any one give me any information on which of these upgrade cards (or
> others) work (or are known not to work) with PowerPC Linux, and Debian in
> particular (I'm running a 2.2.19 kernel if that matters, and have MacOS 8.1).
There are very few hard compatibility problems with upgrade cards, bu a
lot of potential breakage.
First, some of the 7x00/8x00 machines were a little different from
others. Namely, the early batches seem to have had some chips with
slower ratings (slower than spec, it would seem), making those
motherboards behave badly under high bus speeds. So, get an upgrade card
where you can play with the bus speed setting. You may need to tune
those settings a bit to avoid frequent misterious crashes.
Next, there are a few software gotchas. It is said that MacOS and/or the
firmware is not compatible with certain advanced features of the newer
CPUs, namely speculative loads (reading from memory before kowing
whether this read will really be used). That's one reason you get a
software driver with some of these cards, which disables this feature.
This problem can be worked around in the firmware, if need be by
hand-patching nvramrc (done that ;-). Linux doesn't have those problems.
The other reason for a driver is the cache setting. All of these upgrade
boards come with on-board L2 cache, which the computer's firmware knows
nothing about, and thus doesn't enable. The driver corrects that, and
Linux has provisions for also enabling it on user demand.
I also had a problem with MESH SCSI not being able to read my bootdisk
with high CPU and/or bus speed settings (well below spec of both the
computer and the upgrade board). Turns out something somewhere got
_too_fast_, and I needed to slow the CPU down in the firmware to make it
boot. Linux releases that brake later on.
> Also, can anybody tell me (or tell me where to find information on) how
> much of a performance improvement I can expect for typical software
> development tasks (compiling and running Java, C, and C++ programs,
> browsing the web, reading email, etc).
My box is a 7600, originally 604/132 and now G3/300. It does compare
well to my TiBook/400. I still use the 7600 for day-to-day usage, and as
long as you don't need superfast graphics, it still is a very decent
machine.
I did however move most of my Linux partitions to an IDE disk off a
Promise IDE controller, which gives at least double-speed disk access
vs. the built-in SCSI, even more so vs. the original Apple hard disk.
You could also add a modern PCI graphics board, but then again changing
everything is probably more epxensive than just bying a new box.
Depeneds on you what you prefer....
Cheers
Michel
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