Messages in this thread | | | Date | Wed, 12 Nov 1997 16:09:39 -0500 | From | Brian Gerst <> | Subject | Re: SMP kernels and single Cyrix processor problem |
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Linux Developer wrote: > > On Tue, 11 Nov 1997, Brian Gerst wrote: > > > I've been having problems lately with forgetting to unset SMP=1 which is > > enabled by default in the 2.1.x kernels, only to end up with an unusable > > kernel on my cpu/motherboard. I have a Tyan Tomcat IV (SMP capable) > > board, and a Cyrix 6x86L 166+ processor. When the SMP kernel starts it > > immediately oopses after detecting that the motherboard supports SMP, > > even though the processor does not. I have not been able to capture the > > oopses as they scroll by too fast and syslog has not started yet. Is > > there any way I can catch the oopses so I can figure out where it is > > crashing? At least it should determine that the mobo/cpu cannot run an > > SMP kernel and halt with a warning instead of producing the oopses. > > I have spoken with Cyrix about SMP on the 6x86 and 6x86MX series of CPUs a > number of times in the past. Cyrix and AMD both use the OpenPic chipset > for SMP. In order to use a single Cyrix on an SMP board, you must compile > the kernel as single-CPU, and if necessary, set the motherboard to > single-CPU mode. The Tyan Tomcat series shouldn't require this, but you DO > need a single-CPU kernel. Either that or another Cyrix and a dual Socket7 > OpenPic chipset motherboard. ;)
I've found that adding 'nosmp' to loadlin or lilo will allow an SMP kernel to work on a Cyrix. It's just getting quite irritating that SMP is turned on by default in the 2.1.x kernels and it's not a normal config option (out of sight out of mind...)
All the more reason to move SMP to Config.in
Interesting to note though... the SMP kernel still tries to detect a second processor even if nosmp is specified. In my case, it finds a phantom second processor and was probably trying to enable it (and crashing). AFAIK there is no BIOS switch to enable/disable the second cpu, but I do have the single cpu variant of the board (all of which means the second zif socket was not soldered onto the board!).
I am going to try to make a patch to detect if the cpu is really an Intel cpu and disable SMP if otherwise.
--
Brian Gerst
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