[Coco] Re: [Color Computer] Re: Dragon Disk interface

[Gene Heskett]

On Sunday 27 March 2005 23:22, Phill Harvey-Smith wrote:
>Gene Heskett wrote:
>> On Sunday 27 March 2005 22:29, Phill Harvey-Smith wrote:
>>>Gene Heskett wrote:
>>>>On Sunday 27 March 2005 17:48, Phill Harvey-Smith wrote:
>
>[Snip, to keep the length down :)]
>
>>>Hope that wasn't too technical :)
>>
>> Not at all Phill, thanks.
>
>No probs.
>
> > One thing I didn't see mentioned was the
>>
>> data rate the 2797 can run at.  I don't have any data sheets on it
>> here.  Can it do 500 kilobaud and maybe even 1 megabaud?
>
>It will do 500Kbaud, as it was designed to also work with 8" disks
> which IIRC work at this data rate.

Yup.  And the 2.88 and up stuff used 1 megabaud.  I see from the data 
sheet google found me that the max clock is 2 mhz, so the usual /4 
gives a 500 kilobaud max rate.  That will do 1.2's and 1.44's only 
then using the std sector formats.  But, the ability to use a 1.44hd 
disk is something we don't have now.  The 720 DD disks haven't been 
made now in 6-8 years, but they do work with our present controllers 
and 3.5" drives quite nicely.

>>I'm
>> thinking in terms of 1.2 meg and even 2.4 or 2.88 meg disks in the
>> usual 3.5" drive for those drives that can support the original
>> I've Been Moved 2.88 disks.  Probably not many of those left in
>> circulation though.
>
>I have had one version of my development board reading 1.44MB PC
> disks, needed to use the speed up poke to enable the Dragon to keep
> up with the data rate tho.

No doubt.  I hadn't thought of that when I wrote that because I'm used 
to the no-halt controller, which buffers all that in a static ram 
chip right on the controller and would not suffer from that 
limitation.  Unforch, thats socketed for only the 1793 28 pin 
econobox version, darnit.

>> Also, since that chip has probably been EOL'd for a decade now,
>> how are supplies?  More recent, and possibly more capable clones
>> even should be considered.
>
>Managed to get hold of 5 of them last year as new old stock, just as
>spares for my real DragonDos cart, and for projects like this. Main
>benifit is that they are compatible from a software pov, to the
> 1793/1773.

Partminer shows a few yet, but I don't know how the package suffixes 
translate.  Less than 100 for all 4 types they do show.

>>    There was one in common useage on many of the
>> older wintel motherboards back before it all got integrated that
>> was quite versatile, but I don't recall its part number now.
>
>Off the top of my head I can't say I can either, but I do know the
> one you mean.
>
>> I do see, in the present linux floppy driver that has to handle
>> everything that comes down the pike, has formats to as high as
>> 3.84 megabytes on a 3.5" drive.  But I don't see a lot of chip
>> specific stuff there, so maybe I'm looking at the wrong driver src
>> file.
>
>Have not dug around in the Linux kernel much, but yeah should be in
>there as the modern integrated chipsets also emulate it.

Yes, the SuperIO chipset on my previous mobo was pretty good, if you 
could come up with the fdparm file line to describe it, it could 
probably do it.  I've not explored what this newer boards chipset can 
do, but with si real estate fairly cheap, I don't imagine anything 
has been removed in the fuunctionality of it.

This is an intrigueing project Phill, do keep us posted.

-- 
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)
99.34% setiathome rank, not too shabby for a WV hillbilly
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message by Gene Heskett are:
Copyright 2005 by Maurice Eugene Heskett, all rights reserved.


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