2 Jan
2012
2 Jan
'12
9:59 p.m.
On 12/31/2011 07:07 PM, Jerome H. Fine wrote:
SSSD 8" was RX01, RX02 Drives could read and write it b ut RX02 format
was M2FM and not compatable with anything else save for DSD and some
Plessy cards.
RX03 was Two sided RX01 but by time DEC arrived there they decide on the
5.25 80 track single sided (RX50) and later RX33(two sides 800kb and 1.2mb)
and the RQDX controller.
There was also RX05 (basically the PDT11 RX01 format but different logic
based on FDC chip) and there was RX06 a single drive RX01 for VAX780.
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.
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.
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.
The DSD880 did have a Q22 controller as did the DEC RX02(RXV21).
They came later.
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.
Yep. It was designed far enough back that the 2900 based but slice CPU
didn't have enough bits for addressing more and the rice of static ram
was still a factor.
I have a few Qbus DEC systems both PDP11 and VAX.
Allison
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.
