31 Dec
2011
31 Dec
'11
4:07 p.m.
Fred Cisin wrote:
WHAT brand and model computer are you talking about?
On Tue, 27 Dec 2011, Enrico Lazzerini wrote:
The DEC RX02 8" SSDD floppy held 988 data blocks of 512 bytes or
505,856 bytes. While DEC never supported the RX03, the extra code
was included in V04.00 of RT-11, but was removed in V05.00 of RT-11.
The DSD 880/30 had a single functional RX03 floppy drive which could
be used as equivalent to the RX02 drive under RT-11. The RX03 drive
supported the use of a DSDD 8" floppy with 1976 data blocks of
512 bytes or 1,011,712 bytes.
Under DSDD, I believe that each sector was 256 bytes and that
2 sectors were required for each block. The interleave was every
other sector to allow the silo in the controller to be unloaded into
the user buffer. Unfortunately, the DEC RX02 Qbus controller
never supported 22 bit user buffer addresses. However, it was
possible to have a bounce buffer available to the device driver
which could hold the contents of the silo after which the bounce
buffer could be transferred to the user buffer while the silo was
being filled again - during read operations of course.
I presume that larger sectors with fewer inter sector gaps would
have allowed higher capacity. However, the DEC RX02 controllers
had silos of 256 bytes which required the sectors to be the same size.
Well this is all i know:
8"
STAT d:DSK:
9600 r: 128 Byte Record Capacity
1200 k: Kilobyte Drive Capacity
128 d: 32 Byte Directory Entries
128 c: Checked Directory Entries
128 e: Records/ Extent
16 b: Records/ Block
64 s: Sectors/ Track
2 t: Reserved Tracks
2 SIDES
This is that I calculate:
BEGIN SCO2 (1024 bytes/sector) - DSDD 8"
DENSITY MFM ,HIGH
1200K disk capacity is close to maximum for an 8" diskette.
It is what you expect from 8" DSDD. "High" would be incorrect usage, but
from a 5.25" perspective, it fits.
CYLINDERS 77 SIDES 1 SECTORS 8,1024
NO.
You can not get 1200K disk capacity from single sided.
SIDE1 0 1,2,3,4,5,6,7,8,9
SIDE2 0 1,2,3,4,5,6,7,8,9
Those are 10 sectors per side. You said 8
Are you sure that that is the sector sequence?
Here what 22disk tell me:
http://elazzerini.interfree.it/Foto2982.jpg
Where I'm wrong?
1) Instead of transcribing some text, you sent a URL to a picture that is
more than 2 MEGAbytes. (a photograph of your screen?)
THANK YOU for sending the URL instead of attaching it!
A) Not everybody reads their mail in a web browser. Sending a URL
requires cut and paste to get it TO the web browser.
B) Believe it or not, some of us use dial-up! 2M takes too long.
C) Surely that file could be MUCH smaller. Thats a kilobyte for
each character on the screen.
Was it an error message? That would only call for a few lines of text.
Was it a scrambled display, such as non-ASCII characters in filenames?
2) You are posting asking for technical support for an unregistered copy
of a program on a forum where the author is an active participant! If you
REGISTER the program, then he will provide support, maybe even an updated
copy of the program, etc. (It may have additional formats now!)
You didn't tell us the name of the format.
You didn't tell us the form of your calculations. Were they a wild
guess? or did you look at sectors on the disk to determine them?
What "side-pattern" is it? Does it alternate sides before incrementing
cylinder, or does it increment cylinder first, and use the first side
before starting on the second? Does it then go UP the second side, or
DOWN?
You didn't provide us with hex dumps of the directory sectors. NO, DO NOT
SEND US MORE PHOTOGRAPHS! If the problem is in the directory, then
let's see THAT! It's 32 bytes per directory entry/extent - depending on
what the problem is, it might not take more than a few.
