Am 14.06.2010 17:58, schrieb Darren New:
> clipka wrote:
>> (2) Capacity of memory basically has nothing to do with access speed.
>
> Of course it does. You have speed-of-light delay and address line
> cascading to decode. The slowness isn't due primarily to accessing the
> memory cells. It's due to the cascade of gates you have to go thru to
> decode the address to figure out which cell. That's why video memory can
> be so much faster than CPU memory - there's an access pattern (the video
> beam scan) that can be used to speed up address decoding.

If gates are so slow, how come SRAM is so much faster? After all, even 
the memory cells themselves consist of gates there.

I guess the advantage of the access pattern in video memory is a 
different one: It allows easy /prediction/ of the next address to fetch, 
so readout of DRAM cells can be initiated well before the data is 
actually needed, so it's available just in time - farewell latency.

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