Difference between revisions of "Category talk:MSCP Disk Drives"

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:: 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.
 
:: 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 [[protocol]]s 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.
 
:: According to that, the SDB is the lower layer of both the [[Standard Disk Interconnect]] and [[Standard Tape Interconnect]]; "both add higher layer [[protocol]]s 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.
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:: 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. [[User:Jnc|Jnc]] ([[User talk:Jnc|talk]]) 22:25, 30 August 2023 (CEST)
 
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::: 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. [[User:Vaxorcist|Vaxorcist]] ([[User talk:Vaxorcist|talk]]) 11:51, 31 August 2023 (CEST)
 
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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 [https://forum.vcfed.org/index.php?threads/rqdx1-and-rqdx2-woes.58527/ 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.
 
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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 [https://forum.vcfed.org/index.php?threads/mfm-drives-in-at-machines.72535/ here] and especially [https://groups.google.com/g/comp.os.cpm/c/BmmvgA0QGkU 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 [http://www.pdp8online.com/mfm/mfm.shtml here].) That is a poor name, though, because there are lots of drives that use MFM.
 
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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. [[User:Jnc|Jnc]] ([[User talk:Jnc|talk]]) 12:28, 31 August 2023 (CEST)
 
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: The "ST" is "ST506" (sometimes "ST412"), see [https://en.wikipedia.org/wiki/ST506/ST412#Interface_to_controller]. 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. [[User:Vaxorcist|Vaxorcist]] ([[User talk:Vaxorcist|talk]]) 14:56, 31 August 2023 (CEST)
 
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:: I found this page: [https://www.redhill.net.au/d/1.php 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 [http://www.bitsavers.org/pdf/seagate/mfm/ST-506/ST506_Product_Manual_Jul83.pdf ST506 Product Manual] and the [http://www.bitsavers.org/pdf/seagate/mfm/ST-412/ST406_ST412_ST419_Product_Manual_Jan84.pdf 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.
 
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:: 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.)
 
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:: 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'. [[User:Jnc|Jnc]] ([[User talk:Jnc|talk]]) 15:57, 31 August 2023 (CEST)
 

Latest revision as of 04:09, 5 January 2024

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.
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