Re: A86: a question
[Prev][Next][Index][Thread]
Re: A86: a question
At 06:36 AM 4/20/98, you wrote:
>
>At 08:30 PM 4/19/98 -0500, you wrote:
>>
>>Could someone please explain what "T states" mean in relation to Z80
>>processor speed? I looked it up in the Z80 reference book from Zilog, but
>>it didn't explain it.
>>
>>I've never seen "T states" or anything like that when "counting cycles" for
>>the PC (which varies greatly from processor to bus to cache), so does it
>>have to do with bus i/o "cycle eaters"?
>>
>>Please confirm this understanding: a microprocessor's MHz is how many
>>million cycles it executes per second...a 6 MHz processor like the TI-86's
>>runs 6,000,000 cycles per second. An instruction that executes in 5 cycles
>>could be executed 1,200,000 times second. But this seems a little too fast
>>for the calc, but not my 50 MHz 486.
>>
>The MHz is actually the clock ticks or pulses per second. On some
>processors, the cycles for the processor isn't the same as the MHz. For
>example, the PICs' cycle is 4 clock ticks long. But in the Z80 references
>T-states does mean one clock tick, so T-states is the same as the MHz. Look
>at pg. 3-1 in the Z80 User's Manual. They call them T-cycles, but it's the
>same thing. Chapter 3 is on timing, explains how memory reads/writes, i/o,
>etc. is timed, if you're interested.
>
>So anyway, you're right, a 5-cycle instruction should execute 1.2 million
>times a second.
>
>--Joshua
Thanks. But, that sounds like a contradiction: Do you have 6,000,000
million cycles per second, or time states per second? You said they are the
same, but T-states and cycles per instruction are different. What book are
you refering to? I filled out the form on www.zilog.com, and I received the
"Z80 Microprocessor Family--Databook". Is there another one I can receive?
David Phillips
electrum@tfs.net
Follow-Ups: