[Coco] 720k sssd

[Bob Devries]

You need to realise that the default for the Coco whether DECB or OS9 is 
DOUBLE DENSITY (DD), not SD. SD was used mostly on the early TRS-80 Model 1.

Some versions of OS9 (but not the coco version) had track 0 in 
single-density mode.

The density setting changes the rate at which the data is read and written. 
In DD mode that rate is 250KB per second. In SD mode, it is less (128 
KB/sec??), and for 3.5" 1.4MB disks it is 500 KB/sec. The density does not 
set the actual amount of data, since you could specify a single sector per 
track on a DD disk. The density does however set the upper limit of data 
that can be written, since that is a function of time.

Regards, Bob Devries

--
Besides a mathematical inclination, an exceptionally good mastery of one's 
native tongue is the most vital asset of a competent programmer.

Edsger W.Dijkstra, 18 June 1975

----- Original Message ----- 
From: "Stephen H. Fischer" <SFischer1 at Mindspring.com>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Sunday, February 28, 2010 4:12 PM
Subject: Re: [Coco] 720k sssd


> Hi,
>
> That's what  thought.
>
> The Flex disk reading program I remember takes entire control of the disk 
> controller, the first DECB disk reading program did also.
>
> Later the OS-9 disk driver added support for reading DECB disks.
>
> I think that all CoCo disk controllers could do SD.
>
> SHF
>
>
> ----- Original Message ----- 
> From: "Bob Devries" <devries.bob at gmail.com>
> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
> Sent: Saturday, February 27, 2010 8:44 PM
> Subject: Re: [Coco] 720k sssd
>
>
>> The t0s parameter just sets the number of sectors on track 0, not its 
>> density. I think that parameter historically was there to allow for SD 
>> working, but not all controllers can do SD AFAIK.
>>
>> Regards, Bob Devries
>>
>> --
>> Besides a mathematical inclination, an exceptionally good mastery of 
>> one's native tongue is the most vital asset of a competent programmer.
>>
>> Edsger W.Dijkstra, 18 June 1975
>>
>> ----- Original Message ----- 
>> From: "Gene Heskett" <gene.heskett at verizon.net>
>> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
>> Sent: Sunday, February 28, 2010 3:26 PM
>> Subject: Re: [Coco] 720k sssd
>>
>>
>>> On Saturday 27 February 2010, Stephen H. Fischer wrote:
>>>>Hi,
>>>>
>>>>I have read some 5-1/4 Flex disks where the first track was Single 
>>>>Density.
>>>>
>>>>So Single Density disks can be read on a CoCo.
>>>>
>>>>But there may not be an option in Dmode!
>>>>
>>>>SHF
>>>
>>> Yes there is, its the "t0s", and is given in sectors per track just for 
>>> track
>>> zero.
>>>>
>>>>----- Original Message -----
>>>>From: "Ryan Pritchard" <coconut at pritchard.ca>
>>>>To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
>>>>Sent: Saturday, February 27, 2010 6:29 PM
>>>>Subject: Re: [Coco] 720k sssd
>>>>
>>>>>I only have 3.5" 1.44MB and 720KB drives to use with my CoCo, and they 
>>>>>do
>>>>>35 track single sided just fine...  I believe they are doing DD 
>>>>>though..
>>>>>Problem is I don't have many 720K diskettes to use with them to make 
>>>>>the
>>>>>drives work properly.  I am guessing you have some 720K disks that are 
>>>>>SD?
>>>>>
>>>>> Regards,
>>>>>
>>>>> Ryan Pritchard
>>>>> Fun Extends All Basic Life Expectancies
>>>>>
>>>>> On 2010-02-27, at 2:30 PM, Rick Ross wrote:
>>>>>> Does anyone off the top of their head know the dmode for a 3.5 in to
>>>>>> make it sssd?
>>>>>>
>>>>>> Thanks in advance
>>>>>>
>>>>>> Rick
>
>
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