So if the 815 is the stacked dual drive we all know and love

[JohnBuell]

what would the device described in US patent number 4339778 have been? The 816?

Found this with Google's patent search, but you can use your own favorite engine.

[fibrewire]

probably the original intention of the 815, but realized that it is more difficult and costly to design a dual mech / single drive shaft design than to use existing 810 mechs

[Curt Vendel]

I have the schematics to the 816 which appears to be a much better, cost reduced, component reduced design. There is no information on its industrial design however, so it may have been slated to use the same case, or it certainly would've been nice to have seen a side by side, like the Apple ][ drives....

 

BTW - also slated with an 817 as well.... Atari loved its prototypes :-)

 

 

 

what would the device described in US patent number 4339778 have been? The 816?

Found this with Google's patent search, but you can use your own favorite engine.

[carmel_andrews]

Is it true that the 815 was designed to work as four seperate Dbl Dens. disk drives

 

Question is, was that a firmware trick or a software trick

[Rybags]

My impression is that it's 2 seperate single-sided drives only. Using side 2 is a case of flipping the disk over.

 

The only control is assignment as 1/2 3/4 5/6 or 7/8 via physical switch.

[Curt Vendel]

They had settings for drives 1/2, 3/4, 5/6 and 7/8 on the back with selector knobs.

 

DOS 2.0D could handle the devices up to D8:

 

 

 

Is it true that the 815 was designed to work as four seperate Dbl Dens. disk drives

 

Question is, was that a firmware trick or a software trick

[fibrewire]

Is it true that the 815 was designed to work as four seperate Dbl Dens. disk drives

Designed to work as a double-sided double-density drive, as there are additional areas on the PCB for a second set of R/W heads that parallel the existing R/W head circuitry. Also there are dummy entries in the 815 source that indicate the possibility of controlling a second set of heads, and an additional ROM on board that is referenced but not used, as well as 38.4 kbit SIO speeds.

 

I believe the 2nd ROM is present, however it may be empty and only loaded with dummy code for continuity purposes. Or it could contain the missing code to make a DSDD drive!

 

Look at pic #9 here

[+kheller2]

I have the schematics to the 816 which appears to be a much better, cost reduced, component reduced design. There is no information on its industrial design however, so it may have been slated to use the same case, or it certainly would've been nice to have seen a side by side, like the Apple ][ drives....

 

BTW - also slated with an 817 as well.... Atari loved its prototypes :-)

 

 

 

what would the device described in US patent number 4339778 have been? The 816?

Found this with Google's patent search, but you can use your own favorite engine.

 

Got a board layout and screen for that? Hmm.. it would be nice to have some small board that can drive two mechs, enhanced or double density... yes the XF551 board fits that bill.. but I want track buffering.