On 2018-04-12 23:05, Mark Pizzolato wrote:
I've added this to the pdp11_rq.c to describe these values:
/*
MediaId
Is defined in the MSCP Basic Disk Functions Manual, page 4-37 to 4-38:
The media type identifier is a 32-bit number, and it's coded like this:
The high 25 bits are 5 characters, each coded with 5 bits. The low 7
bits is a binary coded 2 digits.
Looking at it, you have:
D0,D1,A0,A1,A2,N
For an RA81, it would be:
D0,D1 is the preferred device type name for the unit. In our case,
that would be "DU".
A0,A1,A2 is the name of the media used on the unit. In our case "RA".
N is the value of the two decimal digits, so 81 for this example.
And for letters, the coding is that A=1, B=2 and so on. 0 means the
character is not used.
So, again, for an RA81, we would get:
Decimal Values: 4, 21, 18, 1, 0, 81
Hex Values: 4, 15, 12, 1, 0, 51
Binary Values: 00100, 10101, 10010, 00001, 00000, 1010001
Hex 4 bit Nibbles: 2 5 6 4 1 0 5 1
The 32bit value of RA81_MED is 0x25641051
*/
Thanks.
No problem. And thanks for clearing up my scribblings. I feared that it
might have been a bit too cryptic.
I'm wondering if the leading first two characters (DU) of the ID is used when a device is
"MSCP Served" by one system out to a cluster at large. This might facilitate
connecting the serving system's local driver to the remote requests.
No idea, but it's definitely possible.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: [email protected] || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
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