Messages in this thread | | | Date | Mon, 16 Dec 1996 16:12:32 +0000 (GMT/BST) | From | Mike Jagdis <> | Subject | Re: Cyrix 6x86 - wierd problem |
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On Fri, 13 Dec 1996, Nigel Metheringham wrote:
> However if run from the rc files on boot, the script consistantly manages > to produce a zero length output (which for some reason is not picked up by > the supervisory script). > > One of the other machines has shown up odd perl problems - script fails to > compile, but then works OK.
With VSPM disabled the immediate candidates appear to be DTE_EN (directory table entry caching), WT_ALLOC (allocate cache lines on write misses as well as read misses), ~SLOP (allow loops to be optimised) and the use of branch prediction for far targets.
> stepping : 1 rev 5
What are the revisions on the other boxes?
> bogomips : 52.33
This is way too low. This seems to suggest that __delay() is being inordinately slow. This should be running straight out of the 256 byte icache so looks like a chip problem. Is it possible that the chip is overheating? Once the system is running it will sleep when idle so will tend to keep its temperature down however under CPU intensive activity or during the boot its temperature will tend to skyrocket if there isn't sufficient cooling. I seem to remember that the Cyrix uses clock skipping if it starts to cook. Perhaps interestingly 52.33 is about half what you get if you build the kernel with 486 alignment optimizations rather than 586. This could be an indication that chip has throttled back to half speed and is powering down on-chip caches.
The other possibility is that the chip has problems with branch prediction but this seems unlikely in the absence of other bug reports.
Mike
-- .----------------------------------------------------------------------. | Mike Jagdis | Internet: mailto:mike@roan.co.uk | | Roan Technology Ltd. | | | 54A Peach Street, Wokingham | Telephone: +44 118 989 0403 | | RG40 1XG, ENGLAND | Fax: +44 118 989 1195 | `----------------------------------------------------------------------'
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