Bug#72479: Data Access Exception
Adam Di Carlo wrote:
>Alan Bain <A.F.R.Bain@statslab.cam.ac.uk> writes:
>
>> I do think something should
>> go in the installation manual for the SPARC version about suggesting
>> that the lowest memory block be contiguous.
>
>> I've checked version 2.2.17 of the install instructions and there is no
>> mention of the problem, which I've confirmed exists on quite a few Suns.
>> I'm happy to write a suitable couple of paragraphs (possibly to go
>> in section 3.3.4 Bad Memory Modules). However I'm not sure to whom I
>> should send this.
>
>Just send the text to be added to the bug report -- I'll catch it and
>include it.
Here is some hopefully useful instructions.
---------------------------------------------------------
Memory Configuration
--------------------
Some older Sun workstations, notably the Sun IPX and Sun IPC have
memory banks located at fixed locations in physical memory. Thus if
the banks are not filled gaps will exist in the physical memory space.
The Linux installation requires a contiguous memory block into which
to load the kernel and the initial ramdisk. If this is not available a
`Data Access Exception' will result.
Thus you must configure the memory so that the lowest memory block is
contiguous for at least 8Mb. In the IPX and IPC cited above, memory banks
are mapped in at 16Mb boundaries. In effect this means that you must have
a sufficiently large SIMM in bank zero to hold the kernel and ramdisk.
In this case 4Mb is NOT sufficient.
Example:
In a Sun IPX you have a 16Mb SIMM and a 4Mb SIMM. There are four
SIMM banks (0,1,2,3). [Bank zero is that furthest away from the SBUS
connectors]. You must therefore install the 16Mb SIMM in bank 0; it is
then recommended to install the 4Mb SIMM in bank 2.
Graphics Configuration
----------------------
Especially in the case of older Sun workstations, it is very common
for there to be an onboard framebuffer which has been superseeded (for
example the bwtwo on a sun IPC), and an SBUS card containing a later
probably accelerated buffer is then plugged in to an SBUS slot.
Under Solaris/SunOS this causes no problems because both cards are
initialised.
However with Linux this can cause a problem, in that the bootprom monitor
may display its output on this additional card; however the linux kernel
boot messages may then be directed to the original on board framebuffer,
leaving NO error messages on the screen, with the machine apparently
stuck loading the Ram Disk.
To avoid this problem, connect the monitor (if required) to the video
card in the lowest numbered SBUS slot (on motherboard card counts
as below external slots). Alternatively it is possile to use a serial
console.
--
Alan Bain
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