root@apal.hanse.de (Andreas Mueller) (11/29/90)
--
FOREVER
{
(This goes to Dave H.)
{
Thanks a lot for your 5 minute :) explanation and the timing sketch, it's
been very helpful.
}
}
So here's my next question:
I've an A1000 with an self build 020/881 board and 512 KByte stat. ram.
(The 020 is a 16MHz type (runs with C7M) the 68881 runs with 20MHz).
I'm working on clocking the 020 with a heigher clock rate.
My idea is to switch between two synchronus clocks (14.3 && C7M)
whenever the CPU 'works' in CPUSPACE || 32 bit ram || AS* is high.
(I've already finished this add on, and it works fine)
Regarding your answer, I'm wondering:
What is faster, 16MHz asynchronus (some waits) or
14.3.. MHz synchronus (no wait !?) clocking?
(Let's say, the KickStart is located in 32 bit ram)
And question number two:
How is the synchronus clocking on the 2620 handled?
-----------------------------------------------------------------------------
+----------------------------------------------------------------------------+
| Andreas Mueller (A1020:) | "Who left his footprints in my computercase?" |
| Phone: +49 040 251 23 27 | "Strong typing is for weak minds!" |
| Hamburg, FRG | |
| UUCP: root@apal.UUCP | |
+----------------------------------------------------------------------------+daveh@cbmvax.commodore.com (Dave Haynie) (12/05/90)
In article <root.3248@apal.hanse.de> root@apal.hanse.de (Andreas Mueller) writes: >I've an A1000 with an self build 020/881 board and 512 KByte stat. ram. >(The 020 is a 16MHz type (runs with C7M) the 68881 runs with 20MHz). >I'm working on clocking the 020 with a heigher clock rate. >My idea is to switch between two synchronus clocks (14.3 && C7M) >whenever the CPU 'works' in CPUSPACE || 32 bit ram || AS* is high. >(I've already finished this add on, and it works fine) In theory, 16MHz 68020s only run down to 8MHz. In practice, switching the clocks will work if you're careful not to glitch the resulting CPU clock, but realize that you will be running the CPU somewhat out of spec. >What is faster, 16MHz asynchronus (some waits) or >14.3.. MHz synchronus (no wait !?) clocking? >(Let's say, the KickStart is located in 32 bit ram) Where are the wait states? If you have the same speed fast memory and simply take synchronization waits when accessing the 68000 bus, my feeling is that the 16Mhz system is faster, especially if you have 32 bit Kickstart as well. Of course, that's "generally faster", anything severly chip ram bound could go slower. If you have only 16 bit RAM, I would expect the 14MHz system to be faster for any real-world application. >And question number two: >How is the synchronus clocking on the 2620 handled? The A2620 always runs with the CPU clocked at 14MHz. It's actually very much like the A2630; it latches data the same way on reads, etc. The main difference is that, being synchronous, much of the logic is simplified since you always know how the CPU and board clocks line up. >| Andreas Mueller (A1020:) | "Who left his footprints in my computercase?" | -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy ONLY 50 MILES TO GO