[Coco] Drivewire for Dummies - Part 1

Fri Mar 23 17:37:56 EDT 2012

Oops, as a developer I tend to use the word "site" a lot more than "sight," 
the truth is out.  And the stubborn side of me refuses spell check as well, 
so I'm sure there are some other typos :)  Glad the basic ideas come across 
though.  And if anyone wants to cut/paste into wiki's/etc, feel free.  You 
can even fix my grammar and spelling.

-Robert

----- Original Message ----- 
From: "Arthur Flexser" <flexser at fiu.edu>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Friday, March 23, 2012 4:02 PM
Subject: Re: [Coco] Drivewire for Dummies - Part 1

> Really an excellent and highly understandable presentation, speaking
> as someone who has never used drivewire or HDBDOS.
>
> One tiny blooper that confused me for a second:  around halfway
> through, you say "Now we get our sites back on drivewire" when you
> meant "sights".  I thought momentarily that you were speaking of
> website data.
>
> Art
>
> On Fri, Mar 23, 2012 at 9:52 AM, Robert Hermanek
> <rhermanek at centurytel.net> wrote:
>> With no prior knowledge I can see how it would be hard to know where to 
>> start, so I'll write a few messages here on the assumption of someone 
>> having no idea what it is for.
>>
>> Background: Once upon a time, if you were lucky you had a color computer 
>> with a disk controller. (If not, you were biting your nails hoping your 
>> cassettes loaded.) If you had a disk system, then you could have up to 4 
>> drives, and they were labelled drives 0 through 3, and you selected which 
>> disk drive you wanted to use with the drive command:
>>
>> DRIVE n
>>
>> Each of these four physical 5 1/4 floppies would store approximately 160k 
>> of data. Back in the day, this was pretty huge. Although disks were more 
>> reliable and much faster than cassette, disk failures or directory 
>> crashes were still quite common.
>>
>> After the floppy era, hard drives started making an appearance. 
>> Harddrives are orders of magnitude larger (megs vs. kilobytes) however 
>> for usage in disk extended basic on a color computer, these larger 
>> devices would still have to be presented as "virtual floppies" of 160k 
>> each, so that a massive rewrite of DECB (disk extended color basic) would 
>> not be necessary, and also to avoid incompatibilities with old software.
>>
>> HDB-DOS appeared on the scene eventually in order to facilitate 
>> connecting to a hard drive from DECB and getting access to your new space 
>> in friendly 160k virtual disks.
>>
>> Next, some very clever folks (insert list of all the geniuses involved 
>> here) came up with "DriveWire." For the coco, it still comes down to be 
>> connected to some large "device." But in fact all read/write disk 
>> requests are redirected out the rs-232 port, and a server application on 
>> the far side (on a modern PC) will respond to the request and send data 
>> back to the coco. The coco sees this data as the response of a sector 
>> read (for example) from a floppy disk, just like back in the day when it 
>> was connected to actual coco disk drives via a disk controller.
>>
>> For drivewire to work then, there are four things you need:
>>
>> 1) a coco running HDB-DOS
>> 2) a cable connecting rs-232 to serial port on PC
>> 3) a drivewire server application running on the PC
>> 4) a disk image mounted and ready in the drivewire server app.
>>
>> Now a little discussion of disk images, and people can correct me if I'm 
>> wrong.
>>
>> Once, disk images (files with a DSK extension) were just a handy way of 
>> storing the data on a 35 track standard coco disk, so again about a 160k 
>> file. This file simply contains each track, each sector, in order, and 
>> the 256 bytes that make up each sector.
>>
>> For the purpose of drivewire however, these DSK images started being 
>> placed in collections, since we didn't want to just work with one virtual 
>> floppy, but many virtual floppies.
>>
>> Going back to the coco running HDB-DOS, there are now two commands for 
>> selecting which drive you want to access:
>>
>> DRIVE n
>>
>> This is the same command I mentioned above, and it will choose which 
>> virtual disk you want to use on the currently selected device. Now for 
>> original coco's running a disk controller, there was no talk of what 
>> device you wanted to access--you were accessing your disk controller, and 
>> if you were lucky you had more than one drive connected to it. You could 
>> then say DRIVE 0 or DRIVE 3 to access your disks.
>>
>> When connecting to scsi devices came about, a new command was added:
>>
>> DRIVE #n
>>
>> Yes, looks the same except for the # symbol. This command selects which 
>> device you want to access. For example, if you had a scsi controller 
>> connected to your coco, with 2 physical harddrives attached, each of 
>> these harddrives would contain their own collections of virtual floppy 
>> disks. So all of the following are possible:
>>
>> DRIVE #0
>> DRIVE 0 - first virtual disk on device 0
>> DRIVE 1 - next virutal disk on device 0
>> (etc)
>>
>> DRIVE #1
>> DRIVE 0 - first virtual disk on device 1
>> DRIVE 1 - next virtual disk on device 1
>>
>> (etc)
>>
>> Now we get our sites back on drivewire, and here is what we come up with:
>>
>> 1) When you use the DRIVE #n command, you are selecting the "device," but 
>> for drivewire this simply means which source file (collection) of virtual 
>> floppies you wish to use. This collection is a single file (like a single 
>> physical harddrive back in the day) that contains, one after another, 
>> virtual floppy disk images.
>>
>> 2) When you use the DRIVE n command, you are choosing which virtual 
>> floppy on the currently selected collection you wish to use.
>>
>> 3) The real bonus: Back in the day with physical devices, you were 
>> limited to how many devices and disks you had by what you really had--in 
>> drivewire there is no limit other than the device and disk #'s have to be 
>> a byte value. That means you can select any device # 0 - 255 (DW4 
>> server), and any drive # 0 to 255 on each device. 256 X 256 = 65,536 
>> virtual disks that can be accessed by a coco connected to a drivewire 
>> server. That's a whole bunch of space!
>>
>>
>> So a final summary is:
>>
>> 1) Get HDB-DOS running on coco, get server running on PC, get connected 
>> with a cable. (we'll get the specifics of the cable soon)
>> 2) In the server application, choose as many disk collections (that will 
>> be seen as "devices" in HDB-DOS) mounted as you would like.
>> 3) Select your current collection from the coco using the DRIVE #n 
>> command, and then choose your current virtual floppy disk using the DRIVE 
>> n command.
>>
>> --
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>> Coco at maltedmedia.com
>> http://five.pairlist.net/mailman/listinfo/coco
>
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