Cc: Bodo Eggert <7eggert@...>, Rene Herman <rene.herman@...>, H. Peter Anvin <hpa@...>, Christer Weinigel <christer@...>, Ingo Molnar <mingo@...>, Paul Rolland <rol@...>, Pavel Machek <pavel@...>, Thomas Gleixner <tglx@...>, <linux-kernel@...>, Ingo Molnar <mingo@...>, <rol@...>
> The last time I heard of a 12 MHz bus in a PC system was in the days of
It wasn't about clone makers speeding up their busses. The ISA bus
originally ran at the CPU clock - 4.77/8/6/10 .. etc. Quite a few board
makers assumed 8MHz and while faster isn't a big problem at 8bit trying
to do the 8/16 bit decode with logic chips at 8MHz is quite tight and
above that generally broke. 8bit tends to work fine because you've got a
lot more timing headroom.
It is about supporting this properly. Properly for ISA devices means
using I/O delays. Properly for chipset devices is probably using udelay.
Linux runs on x86, it isn't limited to PC type architectures at all. We
don't need a BIOS, we don't need legacy compatible I/O devices.
No point. We've got the 64bit kernel for that. That is a much saner
boundary to throw out all the nutty stuff.
Alan
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