Hi Roy! :-)

 RJT> This is going back a few years,  but there was a local computer 
 RJT> store around here that at one time advertised a machine they called 
 RJT> their "Pentium-killer". It was a 486,  but of a special
design,  so 
 RJT> that _all_ of the ram in it was as fast as most cache in those days 
 RJT> was.
Well, the best one could do on a 486 would be to make RAM twice as slow as
the internal cache. I've been reading old reports about the 486 design
lately, and operations with data from the cache take 1 cycle, while going
to main memory has a minimum additional 1 cycle penalty for going to the
on-chip memory interface. Note that it still would require glue logic
between CPU and memory that could do its job "instanteneously",
which is impossible. ;)

Now, maybe the comparision was against the 386s of that day, which had
external cache taking a few cycles to do its work. Still much faster than
going to the real memory.

 RJT> I never did get much in the way of details as to just what 
 RJT> brand of MB or what kind of ram they were using in it back then,  
 RJT> but it sounded pretty nifty...
Yeah, but that was still a CPU running at a rather low frequency (the
fastest true 486 designs run at 120 MHz for AMD and 100 MHz for Intel)
compared to what we have now. Doing something like that would be extremely
expensive now. Intel charges excessive prices for Xeon CPUs with 2M of
cache. That may be for marketing reasons, but in fact it is also not easy
to manufacture a 2M cache that can run at GHz speeds.

Ciao
Pascal

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