Category talk:MSCP Disk Drives

Sub-categories needed

So it turns out that MSCP is a fairly high-level protocol, which runs across several different lower-level hardware interfaces; I found out that the LESI lower-level bus was one that uses MSCP. It turns out that a major one is the Standard Drive Bus, which the RA81 (among many others) uses. I think we ought to have sub-categories of Category:MSCP Disk Drives for each physical bus, as I have done with Category:LESI Disk Drives, and move individual drive articles into the appropriate sub-category (e.g. Category:SDB Disk Drives). So, two questions. i) Is there a good reason not to do this? ii) Are there any physical layers used with NSCP other than LSI and SDB? Jnc (talk) 13:01, 30 August 2023 (CEST)

The RDxx drives are another sub-category of the MSCP main class, but I do not know the name DEC used for the physical layer - maybe we could use "MFM"?

Another (related) thought: Aren't "SDI" and "SDB" two names for the same thing? All RAxx disks are SDI and I think they're SDB, too. To me SDI is much more common than SDB so I'd prefer SDI, but I wouldn't have any serious objections to SDB either. Vaxorcist (talk) 19:30, 30 August 2023 (CEST)

I knew nothing of the later DEC disks; everything in the Standard Drive Bus article I got from the two DEC handbooks listed there. (I don't have them with me at the moment; and neither seems to be available online, alas.) But I'm fairly sure what's in that article is right; I had them right in front of me when I wrote it.

According to that, the SDB is the lower layer of both the Standard Disk Interconnect and Standard Tape Interconnect; "both add higher layer protocols which are adapted to the needs of their supported device types". So we could call them 'SDI disks'; technically, that's totally accurate - almost by definition, all the SDB disks are 'SDI disks'. And you have a good point that SDB is certainly a rare term, and SDI seems to be the more usual one. So I think it makes sense to use Category:SDI Disk Drives for the sub-category.

I don't know what the RDxx disks use for a hardware interface; I will look once the SDI disks are dealt with. MFM, as in Modified Frequency Modulation, refers to how the bits are encoded in the magnetic layer; so unless there is some other expansion of 'MFM', that is not the name of the hardware interface. Jnc (talk) 22:25, 30 August 2023 (CEST)

I already made a class "DEC ST506 MFM Disk Drives" (Sorry, my memory is very weak) - I think ST506 is the name of the hardware interface of the RDxx disks. So "DEC ST506 MFM Disk Drives" could be the MSCP sub-class for the RDxx disks. Vaxorcist (talk) 11:51, 31 August 2023 (CEST)

I looked in all the RD/RQDX documentation there was for a name for the interface to RD-series disks, but could not find one. Something in Mattis Lind's note made me think that it's an industry standard of some sort: "Formatting the disk with a ST class MFM controller". This implies than an RD disk will talk to non-DEC controllers --> the interface to RD disks is an industry standard.

If we knew more about 'ST class MFM controllers', perhaps that would tell us? I put 'ST class MFM controller' into a search engine, and after some reading, it seems that there is something of a standard interface used with early Seagate drives. (Good discussion here and especially here. Effectively an informal predecessor to IDE, but serial instead of parallel.) One person commented "I don't believe there was ever a generic name given to the interface"; people apparently started calling them 'MFM drives'. (Example here.) That is a poor name, though, because there are lots of drives that use MFM.

A name along the lines you used above might work, but it would be absolutely critical to have a page here describing this drive interface 'standard' in some detail, which the category header could link to. Jnc (talk) 12:28, 31 August 2023 (CEST)

The "ST" is "ST506" (sometimes "ST412"), see [1]. All DEC RDxx disks can be used on ordinary early PCs (86/286/386), and some ST506 disks manufactured for PCs can be formatted and used with MicroVAXen and RQDX1/2/3 controllers. I can write a page on the ST506 standard. Vaxorcist (talk) 14:56, 31 August 2023 (CEST)

I found this page: hard drive history - beginings: mfm drives of the 1980s which is a good brief intro. Amusingly (to me), it says "Note: 'ST-412' is correct. You will often see 'ST412' written in error": but if you look at the ST506 Product Manual and the ST412 Product Manual, Seagate themselves didn't usually write 'ST-xxx' (although I did see one instance of that). They generally used 'STxxx', for the ST506, and 'ST xxx', for the ST412.

So, I think some variant of 'ST506' would be the right name, although I'd prefer Category: DEC ST506 Disk Drives. (The 'MFM' kind of irks me, not least because a later 'ST506 interface' drive actually used RLL, not MFM! :-). And yes, it should be a sub-category of the MSCP category. (Note, though, that I have put the SDI/LESI/DSSI disk categories in other categories as well as in Category:MSCP Disk Drives, to make them easier to find - other people might not think to look in 'MSCP Drives' for them.)

Yes, a page called ST506 disk interface or something like that would be good to have; although it should mention up top, where other names for them are mentioned, that many places/people call them 'ST412' and 'MFM disks'. Jnc (talk) 15:57, 31 August 2023 (CEST)

This page calls it the "ST506/ST412 interface", which also a good choice. Jnc (talk) 17:36, 31 August 2023 (CEST)

Just created the page ST506 disk interface before reading your last message. Feel free to rename or improve it! Vaxorcist (talk) 09:51, 1 September 2023 (CEST)

Let me think about the name a bit, and look around to see if other people show any preference between 'ST506' and 'ST506/ST412'. (I personally don't have any preference.) Once that decision has been made, we should make a lot of redirects, though!

I think I can improve the text, and will do so. Jnc (talk) 12:45, 1 September 2023 (CEST)

We also need to think about replacing the technically incorrect Category:DEC ST506 MFM Disk Drives with Category: DEC ST506 Disk Drives. Jnc (talk) 17:39, 29 December 2023 (CET)