14 Dec
2019
14 Dec
'19
1:10 a.m.
Hello,
I also was searching about a clear SMD specification years ago, I found
something in disk documentation from CDC, but doubts remain, because some
disks call the interface SMD, some other CMD, never understood the
difference...
Andrea
14 Dec
14 Dec
1:47 a.m.
On 12/14/2019 1:10 AM, shadoooo via cctalk wrote:
Hello,
I also was searching about a clear SMD specification years ago, I found
something in disk documentation from CDC, but doubts remain, because some
disks call the interface SMD, some other CMD, never understood the
difference...
CMD was the name of the division that manufactured the disks, FWIW.
Not
heard of CDC calling it anything other than SMD.? It was their golden
goose, so though it's not really a spec, reading the specs of any CDC
drive of an equivalent capability as you are looking for is probably
what any standard would contain.
The big problem they faced was there wasn't a second act for them,
despite spending huge amounts on a lot of other products.? They
continued using oddball interfaces to try to pull the same stunt and
people didn't fall for it twice.
The closesest that anyone came to challenging them was the Trident
interface, but they crashed and burned anyway.
When did you see something called CMD?
thanks
Jim
Andrea
2:18 a.m.
l?rdag 14 december 2019 skrev jim stephens via cctalk <cctalk at classiccmp.org
:
On 12/14/2019 1:10 AM, shadoooo via cctalk wrote:
I think the name of the division was MPI. CMD was the Cartridge Module
Drive aka Phoenix.
http://bitsavers.informatik.uni-stuttgart.de/pdf/cdc/discs/CDC_Drive_Models…
But as far as I know the interface of the SMD drives and CMD drives were
identical. At least the Norsk Data ND10 used them both on the same
interface in the computer end.
/Mattis
Hello,
I also was searching about a clear SMD specification years ago, I found
something in disk documentation from CDC, but doubts remain, because some
disks call the interface SMD, some other CMD, never understood the
difference...
CMD was the name of the division that manufactured the disks, FWIW. Not
heard of CDC calling it anything other than SMD. It was their golden
goose, so though it's not really a spec, reading the specs of any CDC drive
of an equivalent capability as you are looking for is probably what any
standard would contain. The big problem they faced was there wasn't a
second act for them, despite
spending huge amounts on a lot of other products. They continued using
oddball interfaces to try to pull the same stunt and people didn't fall for
it twice.
The closesest that anyone came to challenging them was the Trident
interface, but they crashed and burned anyway.
When did you see something called CMD?
thanks
Jim
Andrea
10:58 p.m.
On Sat, Dec 14, 2019 at 2:47 AM jim stephens via cctalk <
cctalk at classiccmp.org> wrote:
CMD was the name of the division that manufactured the
disks,
The division was Magnetic Peripherals Inc. (MPI). I've never heard of it
having been called CMD either before or after it was called MPI. There was
an (AFAIK) entirely unrelated company named CMD Technology Inc. that made
disk controllers.
FWIW. Not heard of CDC calling it anything other than SMD.
According to CDC and MPI documents on various drives, and the SMD/MMD/CMD
specification document:
SMD = Storage Module Drive
MMD = Mini-Module Drive
CMD = Cartridge Module Drive
These were separate groups of products, though they obviously had
similarities, and the interface was essentially identical.
It was their golden goose, so though it's not
really a spec, reading the
specs of any CDC
drive of an equivalent capability as you are looking for is probably
what any standard would contain.
There's most definitely an interface specification that is not specific to
any given drive. For original SMD/MMD/CMD, it is CDC document 64712400,
which went through many revisions, some of which can be found on bitsavers:
http://bitsavers.org/pdf/cdc/discs/interface_specs/64712400_SMDCableSpec_Ma…
The technical specifications of any given drive model give a substantial
faction of the interface specification, but not necessarily all of it.
There are optional features that may not be implemented in a particular
drive model, and a model may have minor deviations from the spec. Also the
interface specification may allow broader ranges of characteristics than
are documented for any given drive. If you're designing an SMD controller
or an SMD drive, you should definitely design to the interface
specification, though looking at individual drive model specs is also
informative.
Unfortunately the later CDC specification for the SMD-E interface (a
superset of the SMD interface) does not seem to be available anywhere. I
think the ANSI specification covers SMD-E, but I'm not 100% certain.
15 Dec
15 Dec
2:05 a.m.
On 12/14/2019 10:58 PM, Eric Smith wrote:
According to CDC and MPI documents on various drives,
and the
SMD/MMD/CMD specification document:
??? SMD = Storage Module Drive
??? MMD = Mini-Module Drive
??? CMD = Cartridge Module Drive
These were separate groups of products, though they obviously had
similarities, and the interface was essentially identical.
Those definitions are
correct, but there was no no difference in the
data interface that we ever worried about with our product.
I don't know that I recall SMD being a product as much as a reference to
the interface they had though.
I've got an MMD160 I hope to restore.? When we were selling systems, we
had both 80mb CMD and 80mb MMD's and they had identical specs as far as
heads and tracks.? Main difference was the CMD top disk could crash as
it wasn't totally sealed.? And our application had no provision to use a
removable platter.
But we ran with the CMD without any problem just to be sure.
There was an EMD line that CDC came out with which had two drives in the
space occupied by an MMD.? If I recall I think the transfer rate was
about twice the rate of the MMD, with larger numbers of bits / track.
For our design, we used a CRC chip to generate and check the recording.?
When the EMD came out, we couldn't get our design modified to use the
preferred ECC chip, and the logic couldn't keep up with the data rate.?
So the controller we had stuck with the original interface.
Thanks
Jim
thanks
Jim
3:32 p.m.
On Sun, Dec 15, 2019 at 3:05 AM jim stephens via cctalk <
cctalk at classiccmp.org> wrote:
I don't know that I recall SMD being a product as
much as a reference to
the interface they had though.
"SMD" was in fact a product name. The CDC976x, BK4XX, BK5XX, BK6XX, and
BK7XX series drives had the official name "CDC(R) Storage Module Drive",
from whence came the "SMD" name for the
interface, starting with the 9760
in 1973. MMD and CMD drives came along a few
years later. AFAIK the MMD
drives weren't too popular in the early years, but gained traction in the
1980s. CMD drives, on the other hand, were an instant hit, starting with
the 9427 "Hawk" drive in 1977.
10:22 p.m.
m?ndag 16 december 2019 skrev Eric Smith via cctalk <cctalk at classiccmp.org>:
On Sun, Dec 15, 2019 at 3:05 AM jim stephens via
cctalk <
cctalk at classiccmp.org> wrote:
The Hawk was quite different from the Phoenix. Actually it was not a
Cartridge Module Drive, rather it was called Cartridge Disk Drive. While
the CMD and SMD drives could be used on the same host interface the Hawk
could not since the interface was different from the SMD interface.
I don't know that I recall SMD being a
product as much as a reference to
the interface they had though.
"SMD" was in fact a product name. The CDC976x, BK4XX, BK5XX, BK6XX, and
BK7XX series drives had the official name "CDC(R) Storage Module Drive",
from whence came the "SMD" name for the interface, starting with the 9760
in 1973. MMD and CMD drives came along a few years later. AFAIK the MMD
drives weren't too popular in the early years, but gained traction in the
1980s. CMD drives, on the other hand, were an instant hit, starting with
the 9427 "Hawk" drive in 1977.
16 Dec
16 Dec
6:26 a.m.
On 12/15/19 10:22 PM, Mattis Lind via cctalk wrote:
While
the CMD and SMD drives could be used on the same host interface the Hawk
could not since the interface was different from the SMD interface.
I've been told by someone who worked down in OK that there were MANY different
OEM variations of the Hawk. I probably have a dozen sets of manuals for them
scanned but not on line. They all share similar Diablo/Pertec style interfaces.
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