Re: LZ: Running Apps. Off Expander
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Re: LZ: Running Apps. Off Expander
>I have been talking to many of my local friends who are very avare of
>hardware and software workings on computers (as am I) and we have come
>to a blank in our pool of knowledge. Is it possible to set up a data
>stream from the memory expander (By Mel Tsai)so that programs could be
>run directly from the expander? If not, why? The transfer rate is
>5kb/S and so i dont think that the prossesor is too fast for the data
>stream...
>Perhaps one of you can fill me in.
5 kilobytes per second is not even close to the speed needed for this!
The Z-80's CALL $xxxx instruction executes in 17 clock cycles. It
involves the movement of 5 bytes (3 bytes of instruction fetch, and
2 bytes written to the stack). Since the Z-80 is running at about
6 Mhz, it is able to do this in 1/352941 seconds. Since it is
transferring 5 bytes in one call, that means that at least for
this instruction, it is transferring 1.76 megabytes per second!
For more typical instruction execution, you still need at least
1.5 megabytes per second! This calculation neglects the time taken
for sending addresses. Since instruction flow can branch and data
access can be anywhere, you cannot just send instructions
sequentially.
(If your PC has 64-bit-wide, 60ns RAM, it can transfer up to 133
megabytes of data per second!)
References: