RE: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
> -Original Message- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Jules > Richardson via cctalk > Sent: 10 October 2017 12:22 > To: cctalk@classiccmp.org > Subject: Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and > IDE ] > > On 10/09/2017 12:52 PM, Chuck Guzis via cctalk wrote: > > On 10/09/2017 06:52 AM, Jules Richardson via cctalk wrote: > > > >> My understanding there is that true SASI supports just a single > >> target, and so there's no selection phase like there is with SCSI > >> (and SCSI provides an extra signal on the connector uses during > >> selection, which simply isn't there with SASI). However, there seemed > >> to be some significant overlap and blurring of lines between SCSI and > >> SASI, such that some early devices calling themselves SCSI aren't > >> quite - and it's possible that some hardware which talks about SASI > >> actually behaves more like SCSI. > > > > I'm not entirely sure about that--the PC Megastore contained both a > > disk and a tape drive. So more than a single device. > > Yes, looking at the Xebec S1410A manual it talks about multiple boards on the > SASI bus, so that appears to be bit rot on my part - I must be thinking of > something which predated SASI. > > Having said that, I think that some bridge boards were capable of driving both > a ST506/412-type disk and QIC tape, so that particular setup wasn't unheard > of, although most bridges handled disk only. > > cheers > > Jules I am pretty sure I had a XEBEC SASI board that would run as SCSI and had 2 x MFM drives as 2 x LUNS onto a single SCSi address... ... on my ATARI ... Dave
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On 10/09/2017 12:52 PM, Chuck Guzis via cctalk wrote: On 10/09/2017 06:52 AM, Jules Richardson via cctalk wrote: My understanding there is that true SASI supports just a single target, and so there's no selection phase like there is with SCSI (and SCSI provides an extra signal on the connector uses during selection, which simply isn't there with SASI). However, there seemed to be some significant overlap and blurring of lines between SCSI and SASI, such that some early devices calling themselves SCSI aren't quite - and it's possible that some hardware which talks about SASI actually behaves more like SCSI. I'm not entirely sure about that--the PC Megastore contained both a disk and a tape drive. So more than a single device. Yes, looking at the Xebec S1410A manual it talks about multiple boards on the SASI bus, so that appears to be bit rot on my part - I must be thinking of something which predated SASI. Having said that, I think that some bridge boards were capable of driving both a ST506/412-type disk and QIC tape, so that particular setup wasn't unheard of, although most bridges handled disk only. cheers Jules
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On 9 October 2017 at 19:52, Chuck Guzis via cctalk wrote: > I'm not entirely sure about that--the PC Megastore contained both a disk > and a tape drive. So more than a single device. Did they have separately-settable IDs? Otherwise, LUNs, I'd think, but I'd also expect that to flummox many drivers. -- Liam Proven • Profile: https://about.me/liamproven Email: lpro...@cix.co.uk • Google Mail/Talk/Plus: lpro...@gmail.com Twitter/Facebook/Flickr: lproven • Skype/LinkedIn/AIM/Yahoo: liamproven UK: +44 7939-087884 • ČR/WhatsApp/Telegram/Signal: +420 702 829 053
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On Oct 9, 2017 11:51 AM, "Mark Linimon via cctalk" wrote: On Mon, Oct 09, 2017 at 08:52:26AM -0500, Jules Richardson via cctalk wrote: > Lots of early SCSI devices have no support for the Inquiry command, which > trips up modern software which expects it - I don't know if it was simply > ignored, or if there was a point in time where it wasn't present in the > spec, and was only added later. When I worked on SCSI device drivers in the late 1980s, we found that support for the full spec was rare. "Get it to work well enough and ship it" seemed to be the explanation. (cf: any BIOS implementation) We wound up using a subset of the spec to get things to interoperate correctly with our cards. Open source kernels from the time had big tables of quirks to cope with dodgy standards compliance. Things haven't changed much: there are still non compliant devices today... don't want to use a feature that has a bug which will eat data... Warner
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On 10/09/2017 06:52 AM, Jules Richardson via cctalk wrote: > My understanding there is that true SASI supports just a single target, > and so there's no selection phase like there is with SCSI (and SCSI > provides an extra signal on the connector uses during selection, which > simply isn't there with SASI). However, there seemed to be some > significant overlap and blurring of lines between SCSI and SASI, such > that some early devices calling themselves SCSI aren't quite - and it's > possible that some hardware which talks about SASI actually behaves more > like SCSI. I'm not entirely sure about that--the PC Megastore contained both a disk and a tape drive. So more than a single device. --Chuck
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On Mon, Oct 09, 2017 at 08:52:26AM -0500, Jules Richardson via cctalk wrote: > Lots of early SCSI devices have no support for the Inquiry command, which > trips up modern software which expects it - I don't know if it was simply > ignored, or if there was a point in time where it wasn't present in the > spec, and was only added later. When I worked on SCSI device drivers in the late 1980s, we found that support for the full spec was rare. "Get it to work well enough and ship it" seemed to be the explanation. (cf: any BIOS implementation) We wound up using a subset of the spec to get things to interoperate correctly with our cards. mcl
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On 10/09/2017 10:42 AM, Jon Elson wrote: On 10/09/2017 08:52 AM, Jules Richardson via cctalk wrote: My understanding there is that true SASI supports just a single target, and so there's no selection phase like there is with SCSI No, not true. Each of the 8 data lines selected one target, so you could have 8 targets on one controller. Yes, you're right... I don't know where I was remembering that from (did SASI grow out of something which was single target?) but I was just looking at the Xebec S1410A manual and it does indeed talk about multiple boards on the SASI bus. cheers Jules
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On 10/09/2017 08:52 AM, Jules Richardson via cctalk wrote: My understanding there is that true SASI supports just a single target, and so there's no selection phase like there is with SCSI No, not true. Each of the 8 data lines selected one target, so you could have 8 targets on one controller. (and SCSI provides an extra signal on the connector uses during selection, which simply isn't there with SASI). However, there seemed to be some significant overlap and blurring of lines between SCSI and SASI, such that some early devices calling themselves SCSI aren't quite - and it's possible that some hardware which talks about SASI actually behaves more like SCSI. Yes, I'm sure this was true, as vendors moved their code over to comply with the new standard. I don't think SASI had any parity support, either - but I think that in a lot of cases early HBA's relied on parity checking in software, which meant that it could simply be ignored. I looked up my SASI interface, and I didn't see any parity circuit there. Jon
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On 10/05/2017 01:50 PM, Chuck Guzis via cctalk wrote: You could well be right--I do recall that there was "Mac SCSI" and then the slightly different "Everyone else's SCSI". I ran into this when talking with some SMS/OMTI engineers about an ST506-to-SCSI bridge board that I have. Their reaction was "Oh, that's Mac SCSI--you want real SCSI". Hmm, I was under the impression that at the connector level the Mac flavor still carries all the signals of real SCSI, but leaves out a lot of the grounds so that it'll fit into 25 pins. At the protocol level, it's the same. At the low-level software side of things, Macs could be picky and only talk to a SCSI device which identified itself with Apple branding - which would certainly cause problems in hooking up something like an OMTI board. I do know that many SASI devices work as SCSI-1 devices. Somewhere, I still have an early PC ISA SASI (not SCSI) adapter for an Ampex Megastore unit. My understanding there is that true SASI supports just a single target, and so there's no selection phase like there is with SCSI (and SCSI provides an extra signal on the connector uses during selection, which simply isn't there with SASI). However, there seemed to be some significant overlap and blurring of lines between SCSI and SASI, such that some early devices calling themselves SCSI aren't quite - and it's possible that some hardware which talks about SASI actually behaves more like SCSI. I don't think SASI had any parity support, either - but I think that in a lot of cases early HBA's relied on parity checking in software, which meant that it could simply be ignored. Lots of early SCSI devices have no support for the Inquiry command, which trips up modern software which expects it - I don't know if it was simply ignored, or if there was a point in time where it wasn't present in the spec, and was only added later. cheers Jules
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On Fri, 6 Oct 2017, Geoffrey Oltmans via cctalk wrote: Supposedly the Mac Plus SCSI implementation is slightly broken/non-standard (or at least draft standard), either in its drivers or the SCSI controller chip, so maybe that's what they were referring to. Even TRIVIAL differences can bite you. Such as Apple/Future Domain? cabling of "TermPwr"
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On Thu, Oct 5, 2017 at 1:50 PM, Chuck Guzis via cctalk < cctalk@classiccmp.org> wrote: > > You could well be right--I do recall that there was "Mac SCSI" and then > the slightly different "Everyone else's SCSI". I ran into this when > talking with some SMS/OMTI engineers about an ST506-to-SCSI bridge board > that I have. Their reaction was "Oh, that's Mac SCSI--you want real SCSI". > > Supposedly the Mac Plus SCSI implementation is slightly broken/non-standard (or at least draft standard), either in its drivers or the SCSI controller chip, so maybe that's what they were referring to.
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On 6 October 2017 at 06:11, r.stricklin via cctalk wrote: > > Notwithstanding the first Macintosh models lacked SCSI entirely. The first > Macintosh with SCSI was the Plus, in 1986. Well, this is true, but then again, there weren't many models of Mac before the Mac Plus, were there? AFAIK there was only the original Macintosh (128 kB RAM) and then the Fat Mac (same machine, but with 512 kB RAM). That's it. No? I have a Plus but it died while I was experimenting and I have the electronics knowledge of an orang utan. How I'm going to fix it, I do not know. -- Liam Proven • Profile: https://about.me/liamproven Email: lpro...@cix.co.uk • Google Mail/Talk/Plus: lpro...@gmail.com Twitter/Facebook/Flickr: lproven • Skype/LinkedIn/AIM/Yahoo: liamproven UK: +44 7939-087884 • ČR/WhatsApp/Telegram/Signal: +420 702 829 053
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On Oct 5, 2017, at 11:18 AM, Tom Gardner via cctech wrote: > I was at Shugart at that time and to the best of my recollection Apple was > not a driver of the ANSI activity. > The Macintosh shipped in January 1984 well after the ANSI SCSI work started > and its major distinguishing feature was the non-standard connector Notwithstanding the first Macintosh models lacked SCSI entirely. The first Macintosh with SCSI was the Plus, in 1986. ok bear. -- until further notice
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On 10/05/2017 09:39 PM, Jerry Weiss via cctalk wrote: > The DK Driver for VMS versions around 5.x definitely had a problem with > non-DEC disks. 6.X and greater were slightly more forgiving. Having many of the era DEC VAX I can say the only SCSI issue I had was the boot disk greater than 1.07 GB. for second or third disks that was not an issue. It was a system diagnostic/boot rom issue. I've used most anything I could find that was SCSI or SCSI-2. Most were Seagate or WD, and a few with Compaq/fujitsu labels. With VMS 5, but not 5.0. Allison > The specifics are summarized in a note from Ralph Weber in > https://groups.google.com/forum/#!search/SCSI$20Mode$20Page$20Requirements$20$20axp/comp.os.vms/RAaUpP_XXEw/BWn64YZYwBQJ > . > > I don’t think there is list of non-DEC disks in the driver as it instead > checked the SCSI Mode bits and other disk configuration settings. There is > a list (table) for DEC Drives (idiosyncrasies?) and another SCSI2 Tagged > Queuing devices requirements used for Clusters in the driver. > > Regards, > Jerry > > > >> On Oct 5, 2017, at 6:23 PM, Peter Coghlan via cctalk >> wrote: >> >> >> >>> The biggest problem you had was the requirement to assert ATN when selected >>> properly.� Later the tag queuing caused huge headaches as manufacturers >>> implemented that feature. >>> >>> It eventually was made mandatory for the most part by linux, and perhaps >>> Windows requiring the tag queuing drilled own to the lowest level of the >>> system's use of the disk. The capability to do that, or fake it is >>> required to allow the kernel to queue commands to run, and have the OS >>> continue to run till command completion. >>> >> I recall VMS having issues with SCSI disks which claimed to do tag queueing >> (and bad block replacement) but didn't do it right, before I'd even heard >> of linux. >> >> Customers complained that VMS refused to work with commodity SCSI disks >> and thought that it was a conspiracy to get them to buy expensive DEC branded >> disks. DEC claimed that only the disks with their firmware did tag queueing >> and bad block replacement correctly. The VMS SCSI driver supposedly had >> (has?) >> a list of specific disks known to mess up which it would refuse to bring >> online. >> >> I wasn't well up on Sun but I expect the same issue existed there too. >> >> Regards, >> Peter Coghlan. > >
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On 10/05/2017 01:50 PM, Chuck Guzis via cctalk wrote: What I found curious was the CDC manual that called SCSI "SASI subset". To me that says that SASI was the more elaborate protocol and SCSI initially picked and chose from it. Oh, no! SASI was VERY simple. You could read and write a number of blocks, and sense the error status. That was just about the total command set. Even SCSI-I had a much wider set, to accommodate tapes, scanners, printers,and other things. It allowed for several different types of status sensing, could report a lot of information about the drive (make & model, physical configuration, etc.) At least the Memorex SASI drive/controller I put on my CP/M system was really basic, as far as I remember. Jon
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
The DK Driver for VMS versions around 5.x definitely had a problem with non-DEC disks. 6.X and greater were slightly more forgiving. The specifics are summarized in a note from Ralph Weber in https://groups.google.com/forum/#!search/SCSI$20Mode$20Page$20Requirements$20$20axp/comp.os.vms/RAaUpP_XXEw/BWn64YZYwBQJ . I don’t think there is list of non-DEC disks in the driver as it instead checked the SCSI Mode bits and other disk configuration settings. There is a list (table) for DEC Drives (idiosyncrasies?) and another SCSI2 Tagged Queuing devices requirements used for Clusters in the driver. Regards, Jerry > On Oct 5, 2017, at 6:23 PM, Peter Coghlan via cctalk > wrote: > > > >> >> The biggest problem you had was the requirement to assert ATN when selected >> properly.� Later the tag queuing caused huge headaches as manufacturers >> implemented that feature. >> >> It eventually was made mandatory for the most part by linux, and perhaps >> Windows requiring the tag queuing drilled own to the lowest level of the >> system's use of the disk. The capability to do that, or fake it is required >> to allow the kernel to queue commands to run, and have the OS continue to >> run till command completion. >> > > I recall VMS having issues with SCSI disks which claimed to do tag queueing > (and bad block replacement) but didn't do it right, before I'd even heard > of linux. > > Customers complained that VMS refused to work with commodity SCSI disks > and thought that it was a conspiracy to get them to buy expensive DEC branded > disks. DEC claimed that only the disks with their firmware did tag queueing > and bad block replacement correctly. The VMS SCSI driver supposedly had > (has?) > a list of specific disks known to mess up which it would refuse to bring > online. > > I wasn't well up on Sun but I expect the same issue existed there too. > > Regards, > Peter Coghlan.
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
The biggest problem you had was the requirement to assert ATN when selected properly. Later the tag queuing caused huge headaches as manufacturers implemented that feature. It eventually was made mandatory for the most part by linux, and perhaps Windows requiring the tag queuing drilled own to the lowest level of the system's use of the disk. The capability to do that, or fake it is required to allow the kernel to queue commands to run, and have the OS continue to run till command completion. I recall VMS having issues with SCSI disks which claimed to do tag queueing (and bad block replacement) but didn't do it right, before I'd even heard of linux. Customers complained that VMS refused to work with commodity SCSI disks and thought that it was a conspiracy to get them to buy expensive DEC branded disks. DEC claimed that only the disks with their firmware did tag queueing and bad block replacement correctly. The VMS SCSI driver supposedly had (has?) a list of specific disks known to mess up which it would refuse to bring online. I wasn't well up on Sun but I expect the same issue existed there too. Regards, Peter Coghlan.
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On 10/5/2017 11:50 AM, Chuck Guzis via cctalk wrote: On 10/05/2017 11:18 AM, Tom Gardner via cctalk wrote: I suspect this might start another discussion, but as I understand it Apple had little to do with the evolution of SASI into SCSI. Shugart Associates published SASI in 1981 and took it to ANSI in 1982 where they renamed it SCSI to avoid using a vendors name. You could well be right--I do recall that there was "Mac SCSI" and then the slightly different "Everyone else's SCSI". I ran into this when talking with some SMS/OMTI engineers about an ST506-to-SCSI bridge board that I have. Their reaction was "Oh, that's Mac SCSI--you want real SCSI". John Henry, the founder was an interesting fellow. "One More Time, Inc". What I found curious was the CDC manual that called SCSI "SASI subset". To me that says that SASI was the more elaborate protocol and SCSI initially picked and chose from it. There was a subset of commands taken from the Adaptec specification for SASI which was share with the initial committee. But the SASI suffered from a number of deficiencies in how it was defined and implemented. The objectives were twofold. Put the large footprint of logic and function in the device(s). The objective was to implement what could be done in the devices to make the initiator end of the interface as simple as possible. (This is the end connecting to systems). The SASI initially as was SCSI transfer protocol was interlocked. The transfer was limited to low transfer rates as every transfer had to wait for the receiving end to acknowledge the receipt of the transfer. Who was interested: The problem that existed at the time was that transmission of data at that time had hit a technical wall. SMD was the dominant technology, and the increase of the transfer rate made it difficult to impossible to do the logic to transfer the data, and also do the error checking / correcting logic with existing logic. We had a disk controller, for example that used a TTL CRC chip. The higher transfer rate CDC drives outran that. Also the existing choices for ECC were not fast enough eiither. So the drive companies with the existing market, CDC and the like were casting about for a byte bus structure that they could dominate and move to. Unfortunately it didn't work out that way for CDC as they could not play the games they had with SMD, and though the supported the early SCSI work, Emulex and LSI Logic (NCR) actually did a lot of the work. Emulex saw SCSI as a dominate or die technology area, and NCR saw it as an opportunity for their semiconductor business. Emulex also had silicon, but the NCR / LSI logic company was actually far better at selling OEM for that purpose. At the system level, Sun was an early adopter, and supporter. Their silicon was NCR and LSI logic supplied. Of course Adaptec supported SCSI from the gitgo as well, as they had invented the protocol. I worked with the committee from the first meetings on. Larry Bouchet, who invented SASI and was committed to making it a standard. At the time plugging into systems was seen as still a viable business. The other things going on at the time, was the rise of 5 1/4" winchesters. There were a few companies who had made a commodity business out of making adapters, and quickly put out SASI then SCSI controllers. They had an interest in making sure that such as CDC didn't integrate the controllers into their products. At the time for a period that was something that they got away with. Eventually all of the companies either were bought out or went on to disk drives (WD was boards, bought out Tandon and jumped over to drives in a painful transition). OMTI, not sure where they went, but they had no other business but boards. And another giant, XEBEC moved to disk controller for the PC. in one of my cabinets I've got a lot of the documents from the beginning if it survived my moves. My company, Irvine Computer was supported by CDC to make a SASI and later a SCSI compatable controller for the CDC quarter inch tape, the Sentinel. I assisted CDC people @ MPI to make the Sentinel have proper function in tape operations, as well as such as the EOT handling. The device truly isn't a QIC write only memory. The tape cartridge design with the rubber band notwithstanding for archival purposes, you could use them for a reasonable period back then and get your data back. Also insisted they allow proceeding after errors. While on the committee, the folks at a large company which was based in Oceanside, starting with A who were making write only QIC drives came into the mix about a year in. They and the disk drive controller folks had no interest in having a useful device defined for the tape. It took some fairly contentious meetings to present how tape was supposed to work as well as how it could work over the SCSI protocol as a serial device to get a reasonable definition into the standard.
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On Thu, 2017-10-05 at 11:50 -0700, Chuck Guzis via cctalk wrote: > > What I found curious was the CDC manual that called SCSI "SASI > subset". > To me that says that SASI was the more elaborate protocol and SCSI > initially picked and chose from it. I think that's just bad/ambiguous wording and the intended meaning was "SCSI (but only the parts that are in SASI)" as distinct from "SCSI (all parts)". p.
Re: The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
On 10/05/2017 11:18 AM, Tom Gardner via cctalk wrote: > I suspect this might start another discussion, but as I understand it Apple > had little to do with the evolution of SASI into SCSI. > Shugart Associates published SASI in 1981 and took it to ANSI in 1982 where > they renamed it SCSI to avoid using a vendors name. You could well be right--I do recall that there was "Mac SCSI" and then the slightly different "Everyone else's SCSI". I ran into this when talking with some SMS/OMTI engineers about an ST506-to-SCSI bridge board that I have. Their reaction was "Oh, that's Mac SCSI--you want real SCSI". What I found curious was the CDC manual that called SCSI "SASI subset". To me that says that SASI was the more elaborate protocol and SCSI initially picked and chose from it. I do know that many SASI devices work as SCSI-1 devices. Somewhere, I still have an early PC ISA SASI (not SCSI) adapter for an Ampex Megastore unit. I'm also well-acquainted with what Andy Johnson-Laird called "SCSI Voodoo" in trying to get several different SCSI devices to work off the same SCSI-2 bus. --Chuck
The origin of SCSI [WAS:RE: The origin of the phrases ATA and IDE ]
I suspect this might start another discussion, but as I understand it Apple had little to do with the evolution of SASI into SCSI. Shugart Associates published SASI in 1981 and took it to ANSI in 1982 where they renamed it SCSI to avoid using a vendors name. To quote from the draft SCSI 1 standard " A commercial small system parallel bus, the Shugart Associates System Interface (SASI), generally met the small system requirements for a device-independent peripheral or system bus and had enjoyed significant market success. It was offered to X3T9.2 as the basis for a standard. X3T9.2 chose the name Small Computer System Interface (SCSI) for that standard and began work at its April 1982 meeting. The present SCSI dpANS is a formalization and extension of the SASI. Many existing SASI devices are SCSI compatible. Since April 1982, X3T9.2 has held plenary sessions, at two month intervals, plus numerous informal working meetings. The original SASI has been extended in a number of ways" I was at Shugart at that time and to the best of my recollection Apple was not a driver of the ANSI activity. The Macintosh shipped in January 1984 well after the ANSI SCSI work started and its major distinguishing feature was the non-standard connector Tom -Original Message- From: Chuck Guzis [mailto:ccl...@sydex.com] Sent: Wednesday, October 04, 2017 1:46 PM To: Fred Cisin via cctalk Subject: Re: The origin of the phrases ATA and IDE [WAS:RE: formatting MFM drives on a IBM PC] As an aside, I picked up a 1986 Wren II full-height manual that discussed the drive and its various interfaces. Sadly, IDE isn't one, but SCSI is referred to as "SASI Subset"; i.e. "SCSI (SASI subset)" That concurs with my observation that SCSI was initially an Apple convention. I can recall conversations about SASI vs. Apple SCSI. --Chuck
