[Coco] COCO FPGA

[Becker, Gary]

I have been thinking a lot about the number of disks to support. I have always had a backdoor method of using the maximum number of disks that DW supported (256). I have a specialty NitrOS-9 driver that can support up to this maximum number. I do not believe NitrOS-9 could actually support that number of disks simultaneously, but the capabilities are there. I have the code written to support 128 disks using DW and 128 using the SD Card. This allows someone to boot with DW and gen a disk on the SD. I am placing the drives on fixed 16 MB boundaries. It would take a 2 GB SD Card to support 128 16 MB disks. Larger disks than 16 MB can be used, but then you would have to skip drive numbers until you get to a spot that does not overlap.

Disk BASIC is different. Actually it is not Disk BASIC, it is using the floppy disk without my modified NitrOS-9 driver. The standard hardware that has everything supports only has 4 drive select lines. I am trying to support those 4 drive selects as disks 0 through 3. But they might have to be drive 1, 2, 4 and 8. I am going to completely ignore the fact that drive select 3 is also the side select for double sided disks. A good thing about the CoCo3 is that the BASIC ROMs are copied to RAM. This allows someone to change the drive select definitions with simple poke commands. So, what I am trying to support under disk BASIC is a total of 16 disks. But only 4 can be useable at a time. Also, it will require a switch to chose between DW and SD Card. So copying between the two is more of a challenge. If there is a program to copy a disk with a single disk drive, then it should not be much of a problem. When it asks to change disk, just flip the switch. But, I am open to other ideas in this area. Software that has its own built in disk support, i.e. Orchestra 90, will just be able to use the standard four disks.

Hope this makes sense to everyone. Also, since the code is still in development, things might change.

Gary

-----Original Message-----
From: Aaron Wolfe [mailto:aawolfe at gmail.com] 
Sent: Saturday, December 24, 2011 11:20 PM
To: CoCoList for Color Computer Enthusiasts
Subject: Re: [Coco] COCO FPGA

On Sat, Dec 24, 2011 at 6:18 PM, Frank Pittel <fwp at deepthought.com> wrote:
> Cool!! I can't wait. How many floppy images will be available? The reason I ask is that around here it's
> impossible to get SD cards smaller then 2gig. :-)
>

This is also why I am a bit surprised to see it implemented in a 100%
fdc compatible fashion, since that would seem to limit use to a 3 or 4
floppy images per card, simply due to the nature of the beast..  not a
big deal given how cheap they are.  or maybe some sort of way to do a
redirect using switches, secret pokes, etc and point to different
places on the card, but that adds a fair bit of complexity.  Anyway,
Gary will do it well, that much I am sure.



> The Other Frank
>
>
> On Sat, Dec 24, 2011 at 01:15:45PM -0600, Becker, Gary wrote:
>> SD storage is coming to the CoCo3FPGA. In one mode, disk images will appear to be floppy disks behind the standard floppy controller. Just as DW can be used today. Not sure when it will be finished. It depends on how much time I have over the holidays to work on it. The code is almost finished and I have started the debug process. So, look for it sometime in January 2012.
>>
>> Everyone have a safe and happy holiday season.
>>
>> Gary
>>
>> -----Original Message-----
>> From: Aaron Wolfe [mailto:aawolfe at gmail.com]
>> Sent: Saturday, December 24, 2011 2:34 AM
>> To: CoCoList for Color Computer Enthusiasts
>> Subject: Re: [Coco] COCO FPGA
>>
>> On Sat, Dec 24, 2011 at 3:17 AM, Mark McDougall <msmcdoug at iinet.net.au> wrote:
>>
>> >
>> >> I know first hand that Drivewire will go well into the future.
>> >
>> >
>> > Personally I don't like DriveWire because it doesn't work with software that
>> > accesses the disk hardware directly. That's not to take anything away from
>> > it, though...
>> >
>> >
>>
>> On the CoCo3FPGA, DriveWire *does* work with software that accesses
>> the hardware directly, because the CoCo doesn't know it's using
>> DriveWire.  The stock DECB rom is running and talking to what it
>> believes is a stock FDC.
>>
>> Funny enough, any storage option that did use the SD card would
>> probably not be so compatible, just as any of the hard drive/flash
>> storage options available to a real coco are not so compatible.
>>
>>
>>
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