Date: Mon, 28 Jun 2004 16:43:53 +0100 From: Mark Benson <[EMAIL PROTECTED]> Subject: Re: [PCI] Cache on MOBO NOT Disabled...
On Monday, June 28, 2004, at 02:51PM, Jim Pendarvis <[EMAIL PROTECTED]> wrote:
That is normal. My Sonnet G4/700 has 256k L2 and 1mb L3. Both are active.
CPUDirector will not let me turn the L2 cache off. The manual says that it will always be enabled at startup, but it could be turned off for testing purposes.
Generally, it would be better to have both turned on.
I have heard rumblings that the built-in (i.e. soldered not slot type) cache on
some 9600s is not capable off running reliably at high bus speeds (50MHz or
faster) therefore, depending on what model of 9600 and what type of cache it
has, it may be better to turn it off if possible.
As Peter mentioned, in the 9600 Kansas/Mach 5 machines, removing the stock CPU card removes the cache because the in-line cache in those machines is on the CPU card.
On the 9500 and pre-Kansas 9600 the cache is soldered down and there is no provision for disabling it with hardware. CPU upgrade makers provide software which is supposed to be able to disable it using low level register settings. However, you can disable the 9500/9600/Genesis cache in hardware by removing resistor R31 from the motherboard. Note that I have never tried this myself. This was reported by generally reliable sources back when these machines were newer.
On the S900 and J700 there is a pair of solder points/holes for a jumper which controls the on-board cache. Some machines were shipped with the jumper pins installed but most were shipped without them. IIRC, shorting these two points disables the cache (jumper installed) and opening them (default, jumper not installed) enables the cache. The jumper point is labeled J38 and you can see a labeled image at <http://www.io.com/~trag> and look for the file name S900_MB_Labeled.jpg.
The PowerTower Pro has a cache socket (the only six PCI slot machine so equipped) and removing the cache is just a matter of physically pulling the cache module from the socket. However, in some cases folks have found their PTPs to be more stable with the cache installed. Perhaps it helps terminate a bus or something.
Jeff Walther
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