[Coco] (no subject)

[Gene Heskett]

On Sunday 13 January 2008, Dave R in Illinois wrote:
>So If I understand correctly, faster memory would help a tad with simple
>
>calculations but when it comes to anything being drawn on screen, the
>
>GIME is the limiting factor, not the ram. Interresting. Reason I ask is,

Faster memory isn't even warm spit, since the gime controls all timing.

>I was interested in building a coco from scratch, similar to CoCoZilla, but
>
>Replacing the 6309/6809 with a Freescale 68HC11 to lower part count.

I don't think os9/nitros9 will run on the hc11 without major surgery.

>
>Thanks a bunch :D
>
>
>
>Dave
>
>
>
>
>
>
>
>
>
>I *think* I have some 120ns stuff in my 2nd coco3 with a half meg board in
>it.
>The 2 megs kit in the main one is 90ns I think. Those both work ok and the
>90ns stuff runs dead cold at the actual clock speed it is being run at. I
>can toss a furniture blanket over it with a photo thermometer under it, and
>the temp rise after several hours is 2 degrees. It also has a 63C09 in it
>and is running on an old AT power supply wired externally. But it isn't the
>memory speed that controls the coco's speeds, its the 'dot' clock speed
>being
>tied to the display standard where the machine was intended to be used. That
>
>is in the general area of 14.3 mhz, and is further divided by either (IIRC)
>8
>for the 3's, and 16 for the originals and 2's to get the actual cpu clock of
>
>(for NTSC, PAL is slightly different) 0.889 mhz for the 1's and 2's, and
>1.79
>mhz for the 3's.
>
>A side comment here, applicable to the 63C09 equipt machines. The cpu is not
>
>the limiting factor for speed, the gime is. Its output drivers are so puny
>they simply cannot drive a memory interface line fast enough to make use of
>faster memory. What we really, really need, is a replacement gime made with
>modern cmos technology. And thumb our nose at the FCC who mandated the noise
>
>abatement design that made it so in the first place, combined with Tandy's
>refusal to apply a shielding scheme that might have actually worked. But I
>digress...
>
>>Dave
>>
>>On Saturday 12 January 2008, Lazy wrote:
>>>Would upgrading the memory in a Coco 2 from 20ns to 10ns provide a
>>>
>>>
>>>
>>>noticeable difference in speed?
>>
>>Since memory speed of the original was about 250ns, and the cycle itself is
>>
>>
>>much longer than that, no. And it may lead to troubles using memory that
>>
>>fast in a circuit designed for 10x slower speeds as the faster memory may
>>
>>suffer from noise glitches the slower stuff ignores.
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>--
>>
>>Coco mailing list
>>
>>Coco at maltedmedia.com <http://five.pairlist.net/mailman/listinfo/coco>
>>
>>http://five.pairlist.net/mailman/listinfo/coco
>
>--
>Coco mailing list
>Coco at maltedmedia.com
>http://five.pairlist.net/mailman/listinfo/coco



-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
No two persons ever read the same book.
		-- Edmund Wilson