[comp.sys.apple] 65816 as a Harvard machine

jason@madnix.UUCP (Jason Blochowiak) (03/10/90)

toddpw@tybalt.caltech.edu (Todd P. Whitesel) writes:
> [Deleted discussion of the '816's ALU size, etc.]
> Caching direct page on chip and harvard architecturing it with the ALU would
>be even better.

	Harvard on an '816? Do you know how many programs that would kill?
I shudder at the thought... Perhaps a mode for it, but given my (minimal)
understanding of the matter, that'd be mighty difficult to do. 

	On-chip caching in basically any form, though, would be great.

>Todd Whitesel
>toddpw @ tybalt.caltech.edu

-- 
                      Jason Blochowiak - jason@madnix.UUCP
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toddpw@tybalt.caltech.edu (Todd P. Whitesel) (03/10/90)

jason@madnix.UUCP (Jason Blochowiak) writes:

>toddpw@tybalt.caltech.edu (Todd P. Whitesel) writes:
>> [Deleted discussion of the '816's ALU size, etc.]
>> Caching direct page on chip and harvard architecturing it with the ALU would
>>be even better.

>	Harvard on an '816? Do you know how many programs that would kill?
>I shudder at the thought... Perhaps a mode for it, but given my (minimal)
>understanding of the matter, that'd be mighty difficult to do. 

>	On-chip caching in basically any form, though, would be great.

I meant harvarding the CACHE with the ALU. As long as you allow the separate I
and D cahces to act like standard memory as well, it breaks nothing and allows
many operations (especially zero page and stack) to execute in parallel, thus
shaving off quite a few cycles on the most commonly used instructions.

Executing code out of the D cache would slow things down, sure, but would be
not be hard to do on chip. (Ok, so the cache coordination could get a bit messy
... It looked like a cheap win if it could be done so I thought I'd mention it.)

Todd Whitesel
toddpw @ tybalt.caltech.edu