Optron #26 31 марта 1999

Доработки     Железо

Opinion - Kontorller Beta Disk Interface: simplification without consequences.

      Simplification - without consequences?

{} S. Filimonov, 1999


            ... After the removal of the cecum

            patient began to see better.


                             Felix Krivine


  More recently, in inexperienced users a broad popular one - 
and a lot cheaper - to sell at Lviv radio market device, known 
as "The controller at RT4. Often hear: "He's better than a 
standard floppy disk controller Beta Disk Interface (BDI), and 
all the rest! He has - a few (!) smaller size and consumption. 
There is very clever loop. And anyway ... "And, of course, the 
main argument:" It is much cheaper! " 

  I conducted a comparative analysis of schemes and the BDI
before us devaysa. I dare suggest that our device is the result 
of alteration (or rather - to simplify) BDI. Therefore, there 
is every reason to continue to call the BDI "prototype". 

  So, the fact is that the developer
so simplified their offspring compared with the prototype, 
which severely eroded the number of its performance. Of course, 
with decreasing number primenyamyh chip consumption, 
masgabarity and cost are reduced - but at what cost?


  Let's try together to understand this
difficult question.


  Device can serve no more than two
disk drives (and in fact a normal controller
must serve up to four).

  Trigger mode setting is implemented ...
Say, a bit unusual - the inverter with open collector (resistors
collector load implement mounting
OR). To fully appreciate its beauty -
look at the chart (I'll submit it
also not quite the usual form):


                           + 5



      1 o 1 o

     LN2 LN2

*
*


  What?

  Adds piquancy to the fact that in the latter samples devaysa 
instead of RT4 (with open-collector) used RT11

(Without it). A trigger signal installation
go directly to that RT. (There have been persistent rumors 
that, if applied RT11, the trigger for the stability of the 
resistance of the aforesaid should rezstorov reduced to 150 
ohms.) 

  The question, of course, debatable, but personally I do not
would like to see me in a sort of
Device mode asking such things.

  When connected to a computer devaysa
problems: it (again -
for the sake of simplicity) is missing a signal block 
ports-OUTIORQ. This signal has to generate extra. How proposes 
to do this the developer - the diodes and resistors - to put it 
mildly, not the best solution. I myself had the opportunity see 
unstable operation of the scheme. And what a poor debugger - to 
guess at What is the reason: whether in a RT4 (one more gift! 
"), whether in the trigger mode, or in diode-resistor ladder?


  And if your computer has more and 128K
memory, it is necessary, but the shaper signal-OUTIORQ, mount 
and more dynamic scheme off the controller 128th mode - on the 
unencumbered LN1 element (if it is, of course, the board 
computer available). But then it is appropriate ask: "Why, 
indeed, need controller? After all, commercials can be just as 
easily sell the chip and KR1818VG93 saying: "It is my

controller, only it needs a little more binding. "

  The button "MAGIC", responsible for the removal of all
memory to disk, work on opening
(Developer stingy to the inverter). A
because the buttons are known to have peccadillo:
Soldered to end up like him Wire
and become useless contacts. So
can you imagine what would happen if
this information on your disk.

  In general, as is the case with a trigger mode, the desire to 
save all changes reasonable limits. And it is typical

for the entire circuit solutions devaysa!

  And where did the "Legend of ingenious
PLL - I do guessing. Being
Maybe someone inexperienced users found
that, "If there is such a tricky thing, as
RT4, then it surely must be sewn
no less cunning loop "?

  The fact that in the prototype there are no
no loop. There are mechanisms that synchronize the speed of 
rotation of the disk (and synchronization, and loop - it is 
said in Odessa, two big differences "). Implemented this scheme 
with IE10 - fully replicated in our devices. 

  And at RT4 in devayse implemented decoder
address - yes, in addition, still incomplete, the
compared with the prototype. If we compare
consumption of RT4 and rassypuhi, "which
This decoder is made in the prototype, then
immediately the question arises - what's the payoff?

  The disadvantages devaysa I would mention also
its absence of an input buffer on the bus
data, because when you connect the drive controller processor 
may be heavily overloaded (oh, like users "to hang a bunch of 
bells and whistles on percent!) 

  And finally, get my money
Motherboard devaysa leaves much, much
desired. Controllers collected on them,
obtained as a kind of "disposable" - Non-Repair. Replace - with 
no well-known consequences - in this board inoperable or burnt 
chip is not possible. But the cost of

manufacture of boards, of course, below!


  So now I can only repeat the address of those who are tempted 
- quite clear - a low cost devaysa, the words of Pushkin:



  And he said Balda reproachfully:

  - Do not chase would you, Pop, for cheapness!