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RQDX and MFM disks
Formatting non-DEC disks in the MicroVAX/VAXstation-2000
--------------------------------------------------------
Some of this information I figured out by reading STARLET and the
example device drivers in the VMS _Device Support_ manuals. Much of
it was contributed to me by Terry Kennedy, Lennart Boerjeson, and
others.
The standard DEC drives that are supported in the VS2000 and their
industry equivalents are:
RD54 - Maxtor XT-2190
RD53 - Micropolis 1325 or 1335
RD32 - Seagate ST-251-1
If you have any of these standard drives you can simply plug it into
your 2000 and the ROM formatter will automatically recognize the drive
types. I've never seen this fail, even if the drive has never seen a
DEC machine before, or even if the drive was previously formatted in
a PC.
If the VS2000 ROM formatter program does not recognize one of these
drive types, then it will enter a dialog asking you to enter the drive
parameters described below. Again, I've never seen this fail, even
with very old ROM firmware versions (v1.2 is the oldest I've seen).
If you get a "??" response rather than the dialog, you almost certainly
have a hardware problem with your drive.
In theory you can use ANY MFM drive in the VS2000 by calculating
the appropriate parameters. I've done this with several non-DEC
drives with good success now, and following is a description of what
I've learned about the parameters. If you can contribute to any
of the "I don't know" parts, I'd like to hear about it!
------------------------------------------------------------------------
XBNSIZ - I've no idea what an XBN is! All DEC's disks seem to use 54,
regardless of the disk capacity.
DBNSIZ - number of diagnostic blocks. DEC seems to select this so that the
DBNs and XBNs total up to 1 cylinder. Therefore:
DBNSIZ = (SURPUN*17) - XBNSIZ
LBNSIZ - total number of user data blocks, not counting DBNs and XBNs.
I believe that
LBNSIZ = CYLPUN * SURPUN * 17
the numbers I have for DEC disks are close to this, but not
exact. There must be some ambiguity about what gets counted.
RBNSIZ - replacement block count (for bad block revectoring). About 0.1%
to 1% of the disk capacity is reasonable, depending on the media
quality. DEC seems to always use 0.2%. This is frequently
rounded to an exact number of cylinders, but I'm not sure that's
necessary. WARNING - if you allocate fewer RBNs than your disk
has bad sectors, the VS2000 formatter seems to hang in the media
analysis phase!
SURPUN - surfaces (aka heads) per drive. Note that the RQDX? will ALWAYS
assume 17 sectors per track, 512 bytes per sector! The RQDX
controllers can handle a maximum of 16 heads.
CYLPUN - cylinders per drive. Total number of cylinders on the drive.
I believe, but I'm not sure, that this does NOT include the
cylinders used for DBNs, RBNs and XBNs. Note that the RQDX
family controllers can handle a maximum of 2048 cylinders
(but I don't think there were ever any MFM drives made with
even close to that number!).
WRTPRC - cylinder to start write precompensation. If your drive doesn't
need write precomp (almost none do), then enter a value larger
than the last cylinder.
RCTSIZ - size of the Replacement (i.e. Bad Block Replacement) and Caching
Table. From the structure of the RCT, I believe this can be
calculated as
RCTSIZ = (44 + 4*RBNSIZ) / 512
but unfortunately this doesn't give the values DEC uses for
their drives! You could also just use the RCTSIZ from the
closest sized DEC disk.
RCTNBR - number of copies of the RCT. I'm not sure of the significance
of this, but DEC disks always use 8.
SECITL - sector to sector interleave. The RQDX is fast enough to support
1 (i.e. no interleaving). Anything larger will reduce thruput.
SECITL is a function of the disk rotational speed, and is the same
for all MFM drives regardless of capacity.
STSSKW - delay for switching heads. I don't know how to calculate this or
even what units it's expressed in! All drives seem to use 2.
CTCSKW - delay for track-to-track seek. I don't know how to calculate this
or even what units it's expressed in! All DEC drives use 8.
MEDIAI - media identification code. This is a 32 bit value which the ROM
wants you to enter in DECIMAL, not hex! Standard values are:
RD32 - 627327008
RD53 - 627327029
RD54 - 627327030
The last section explains how the media id is calculated if you
are interested. If you use a non-DEC media id, be aware of two
things: (1) the ROM disk diagnostic won't work, and (2) the VMS
MSCP cluster server won't serve the disk.
------------------------------------------------------------------------
Here are the parameter values for some DEC disks, and those that I've
successfully used for a Seagate ST-4097 (an 80Mb drive).
RD54 RD53 ST4097
------ ------ ------
XBNSIZ 54 54 54
DBNSIZ 201 82 99
LBNSIZ 311256 138672 156060
RBNSIZ 609 280 306
SURPUN 15 8 9
CYLPUN 1221 1020 1021
WRTPRC 1221 1020 1024
RCTSIZ 7 5 5
RCTNBR 8 8 8
SECITL 1 1 1
STSSKW 2 2 2
CTCSKW 8 8 8
MEDAI 627327030 627327029 627327029
------------------------------------------------------------------------
Media Identification Code
The media id is a longword (32 bit) value composed of five 5-bit
alphabetic characters and one 7-bit binary value. The five characters
start from bit 31 (the MSB) of the longword and are encoded as 0=null,
1='A', 2='B', etc. Only letters (and a null) can be represented.
The first two characters represent the media type (e.g. "DU") and
the next three are the name of the media currently mounted (e.g.
"RD" or more accurately, "RD").
The 7-bit binary value is the numeric part of the media name
(e.g. 32, 53, 54, etc).
For example, for an RD54 we have
D U R D 54
00100 10101 10010 00100 00000 0110110
Write this down as a 32 bit hex value and we have 0x25644036 or
627327030 (decimal).
------------------------------------------------------------------------
If he couldn't figure out the answers to the VS2000 formatter, he's
not going to have any easier time with ZRQC! Remember, he's formatting
disks that have never been formatted on a VS2000 or RQDX3 before, so
he needs all the numbers necessary to MSCP-qualify the disk.
Here's the RD52 numbers, straight from the RQDX3 DEC-internal docs:
Quantum Atasi
------- -----
Sector Interleave 1:1 1:1
Bytes/Sector 512 512
Sectors/LBN 1 1
LBNs/Track 17 17
Tracks/Group 8 7
Groups/Cylinder 1 1
Cylinders/Unit 512 645
Total LBN's/Unit 69632 76755
RBNs/Unit 168 168
RCT Size (Blocks) 4 4
RCT Copies 8 8
DBNs/Unit 8 8
XBNs/Unit 54 54
User LBNs/Unit 60480 60480
User Capacity (Bytes) 30965760 30965760
Step Pulsewidth (usec) 11.2 11.2
Step Rate (usec) 17.6 17.6
Write Precomp (nsec) 10 10
Precomp Cylinders 256-611 320-644
And, for completeness, the RD51 and RD53 numbers (though I suspect
the DEC tables have typos for at least some of the RD51 quantities):
RD51 RD53
---- ----
Sector Interleave 1:1 1:1
Bytes/Sector 512 512
Sectors/LBN 1 1
LBNs/Track 18 17
Tracks/Group 1 8
Groups/Cylinder 4 1
Cylinders/Unit 306 1024
Total LBN's/Unit 22032 139264
RBNs/Unit 144 280
RCT Size (Blocks) 36 5
RCT Copies 4 8
DBNs/Unit 87 82
XBNs/Unit 57 54
User LBNs/Unit 21600 138672
User Capacity (Bytes) 11059200 71000064
Step Pulsewidth (usec) 11.2 11.2
Step Rate (usec) 17.6 17.6
Write Precomp (nsec) 10 (none)
Precomp Cylinders 110-305 (none)
Tim Shoppa
------------------------------------------------------------------------
What jumper seting are required to make a Micropolis 1325 look like a RD53 ?
Unscrew the two screws holding the circuit board to the bottom of the drive
and carefully lift it up. Along one edge of the circuit board you will find
a place where it would appear that a resistor should be -- this place is
marked R7. Solder a jumper into that spot to make this drive into an RD53.
Set the drive select jumper to DS2 and you should be in business.
Bob Hoffman
