[cctalk] Re: Bomar 901b My wife found in my stuff. Is this as scarce at it seems?s,?
At first I misread the subject as my 901lb wife…. Man I need my eyes checked! ;o) Don Resor Sent from someone's iPhone > On Apr 15, 2024, at 7:04 PM, ED SHARPE via cctalk > wrote: > > Bomar 901b My wife found in my stuff. Is this as scarce at it seems?s,? > > > Sent from AOL on Android >
[cctalk] Re: PDP-11 thingy. What is it?
On Wed, Apr 10, 2024 at 8:07 PM W2HX via cctalk wrote: > 1. I have read that the card and the drives were compatible with the dec rx02 > drives. Why would the CRDS even bother to redesign a card where DEC had > perfectly good working ones? Anyone know if there is any value in keeping the > FC-202 or just keep with the DEC cards? The easy first answer is DEC's drives were expensive so there was room for competition to bring in a less expensive product and then _they_ would get the profits. The second answer is that DEC's implementation was basic - read and write single-sided floppies and that's it - no media (re)formatting. Third parties could add features to extend what DEC had. The DEC implementation relied on a custom processor board inside the disk drive and a unique/proprietary way to have the controller tell the drives what to do. By the late 80s. Shugart interface drives were plentiful and processors like the Z-80 were totally capable so there were several RX01 and RX02 imitators. I have at least one Qbus card that just has a Shugart interface and was connected to a standard floppy drive mechanism (and it can low-level format disks). In order to work with existing drivers, though, the third party cards did have to emulate them at the I/O register level but as long as it's registers on one end and 8" media on the other, they were free to reimplement the middle part. -ethan
[cctalk] Bomar 901b My wife found in my stuff. Is this as scarce at it seems?s,?
Bomar 901b My wife found in my stuff. Is this as scarce at it seems?s,? Sent from AOL on Android
[cctalk] Re: IBM 350 disk and 305 drum [WAS:RE: Re: Drum memory on pdp11's? Wikipedia thinks so....]
On Mon, 15 Apr 2024, Tom Gardner via cctalk wrote: The IBM 350 disk storage (RAMAC) has 5 million 6-bit characters or 3.75 MB; the actual recorded characters were 8-bits in length including a parity bit and a stop bit for each recorded 6-bit character It was announced as part of the IBM 305 RAMAC system which had drum memory which as far as I can tell had 24 tracks of 100 6-bit characters = 14,400 bits or 1.8 kB Source: http://bitsavers.trailing-edge.com/pdf/ibm/305_ramac/22-6264-1_305_RAMAC_Manual_of_Operation_Apr57.pdf pgs 17 &18 If anyone has a better number please post it Here's what info I have on the RAMAC, from multiple sources, but derived at least partially, if not entirely, from some of Tom Gardner's earlier posts. RAMAC 50 user disks (dummy disks at end to reduce turbulent buffeting) 100 sides, 100 user tracks per side (2 test only tracks on inside and outside) A RAMAC character has 8 bits: 1 start bit, 6 data bits, and 1 parity bit. - clarification by Tom Gardner & Joe Feng 5 sectors per track, 100 characters per sector - Grand total of 50 disks x 2 sides/disk x 100 user track/side x 5 sectors/track x 100 char/sector = 5,000,000 characters Claimed average access time 0.6 seconds, you define "average" movements ;-)) However, the "IBM 650 RAMAC - Manual of Operation - Preliminary Edition" states that the worst case seek, from inner track of top disk to inner track of bottom disk, was 0.8 seconds !! (I *really* want to see that!!) ) 2 heads, one for tracks on top side of each disk, one for bottom side - head assembly moves vertically to selected disk, then goes to selected track - about 200 bits per inch - the magnetic tape density of the period. 2 hp drive motor drives the disks at 1200 RPM, 1/3 hp motor at 3450 RPM drives clutches at 1000 RPM one revolution of fully locked clutch drives arm 6 inches either in/out or up down - 100 inches or 8.3 feet per second - 200 disks per second or 2000 tracks per second Wikipedia: RAMAC mechanism at Computer History Museum The IBM 350 disk storage unit, the first disk drive, was announced by IBM as a component of the IBM 305 RAMAC computer system on September 13, 1956.[8][9][10][11] Simultaneously a very similar product, the IBM 355 was announced for the IBM 650 RAMAC computer system. RAMAC stood for "Random Access Method of Accounting and Control." The first engineering prototype 350 disk storage shipped to Zellerbach in June 1956;[12] however, production shipment announced to begin "mid-1957"[13] may not have occurred until as late as January 1958.[14] Its design was motivated by the need for real time accounting in business.[15] The 350 stored 5 million 6-bit characters (3.75 MB).[16] It has fifty 24-inch (610 mm) diameter disks with 100 recording surfaces. Each surface has 100 tracks. The disks spun at 1200 RPM. Data transfer rate was 8,800 characters per second. An access mechanism moved a pair of heads up and down to select a disk pair (one down surface and one up surface) and in and out to select a recording track of a surface pair. Several improved models were added in the 1950s. The IBM RAMAC 305 system with 350 disk storage leased for $3,200 per month. The 350 was officially withdrawn in 1969. U.S. Patent 3,503,060 from the RAMAC program is generally considered to be the fundamental patent for disk drives.[17] This first-ever disk drive was initially cancelled by the IBM Board of Directors because of its threat to the IBM punch card business but the IBM San Jose laboratory continued development until the project was approved by IBM's president.[18] The 350's cabinet was 60 inches (152 cm) long, 68 inches (172 cm) high and 29 inches (74 cm) wide. The RAMAC unit weighs about one ton, has to be moved around with forklifts, and was frequently transported via large cargo airplanes.[19] According to Currie Munce, research vice president for Hitachi Global Storage Technologies (which acquired IBM's storage business), the storage capacity of the drive could have been increased beyond five million characters, but IBM's marketing department at that time was against a larger capacity drive, because they didn't know how to sell a product with more storage. None-the-less double capacity versions of the 350 were announced[8] in January 1959 and shipped later the same year. In 1984, the RAMAC 350 Disk File was designated an International Historic Landmark by The American Society of Mechanical Engineers.[20] In 2002, the Magnetic Disk Heritage Center began restoration of an IBM 350 RAMAC in collaboration with Santa Clara University.[21] In 2005, the RAMAC restoration project relocated to the Computer History Museum in Mountain View, California and is now demonstrated to the public in the museum's Revolution exhibition.[22] My own text, based on newspaper histories: In 1958, Nikita Khruschev visited USA, to try to de-escalet the cold war a little. When he was refused permission to go
[cctalk] IBM 350 disk and 305 drum [WAS:RE: Re: Drum memory on pdp11's? Wikipedia thinks so....]
The IBM 350 disk storage (RAMAC) has 5 million 6-bit characters or 3.75 MB; the actual recorded characters were 8-bits in length including a parity bit and a stop bit for each recorded 6-bit character It was announced as part of the IBM 305 RAMAC system which had drum memory which as far as I can tell had 24 tracks of 100 6-bit characters = 14,400 bits or 1.8 kB Source: http://bitsavers.trailing-edge.com/pdf/ibm/305_ramac/22-6264-1_305_RAMAC_Manual_of_Operation_Apr57.pdf pgs 17 &18 If anyone has a better number please post it Tom -Original Message- From: Mike Katz Sent: Monday, April 15, 2024 9:33 AM To: General Discussion: On-Topic and Off-Topic Posts Cc: Douglas Taylor Subject: [cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so There was drum storage for the early PDP-8 the "Straight 8", PDP-9 and PDP-10. Each drum stored 32,768 words. Up to 8 of them could be connected for a total storage of 262,144 words of storage. IBM made a 5BM drum storage unit that was the side of a small refrigerator: The RAMAC's disk storage unit, the IBM 350, weighed over a ton, had to be moved around with forklifts, and was delivered via large cargo airplanes. It stored approximately 5MB of data: *five million 8-bit characters on fifty 24-inch-diameter disks*, a form of drum memory.
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
Don't know if it's germane, but the CDC STAR-100 (Cyber 200 series) MCU used a small drum. 70s-80s. Don't recall if the stations did also. There was the "STAR Drum" blue sky that was part of the boilerplate in proposals at the time. STAR had a 512-bit wide data channel reserved for a paging device. I recall Neil Lincoln relating that they tinkered with a 100K RPM drum, but could never get it to operate for more than a few minutes. Then there was SCROLL, also mentioned in the proposals. A very wide tape wrapped around a multi-head rotating drum. I don't know if that one ever got past the pencil-and-paper stage. --Chuck
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
On Mon, Apr 15, 2024 at 12:53 AM Christopher Zach via cctalk wrote: > Was reading the Wikipedia article on Drum memories: > > https://en.wikipedia.org/wiki/Drum_memory#External_links > > And came across this tidbit. > > As late as 1980, PDP-11/45 machines using magnetic core main memory > and drums for swapping were still in use at many of the original UNIX > sites. > > Any thoughts on what they are talking about? I could see running the > RS03/RS04 on a 11/45 with the dual Unibus configured so the RS03's talk > to memory directly instead of the Unibus, but that's not quite the same > as true drum memory. Yep. > Closest thing I remember was the DF32 on a pdp8 which could be addressed > by word as opposed to track/sector. Yes. And the RF series (RF08 and RF11). UNIX on the PDP-11 in 1972 required an RF11 for swap. As mentioned in other replies, the media isn't cylindrical but it behaves logically like a drum. -ethan
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
> On Apr 15, 2024, at 1:15 PM, Tom Uban via cctalk > wrote: > > I recall around 1980, the "A" machine at Purdue University Electrical > Engineering, a PDP-11/70 running Version 7 Unix had a RS04 drum drive used > for swap. It was getting long in the tooth and when a power failure occurred, > someone would have to get a wrench to help spin it up as the head lubricant > was no longer as good as it once was... RS04 is a fixed head disk, similar properties as a drum but shape-wise it's a flat platter with heads on one side. The "lubricant" bit reminds me of our college RF11 swap disk (for RSTS/E). When we got the RP04 it was no longer so interesting so it was not configured in, but it was still powered up. One day I noticed that the "timing track error" light was lit, and since the system was under contract we called DEC field service to repair it. The local tech checked things out and realized the drive was not spinning even though it had spindle power. Oops. He took the drive apart and discovered that the heads had landed, and melted so they were essentially hot-melt-glued to the platter. Those drives use rather low powered motors, intentionally, so with the heads stuck it would not spin up. He ended up replacing all the heads and the platter, not sure about the motor. Got an alignment disk and timing track writer from Maynard, and had to figure out how to use these -- the documentation was sparse, to put it politely. In the end, everything worked. Oh by the way, I don't think that field repair of a drive like that was a standard procedure, but for Jim Newport this wasn't a big deal. paul
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
On Mon, Apr 15, 2024 at 10:19 AM Rick Bensene via cctalk < cctalk@classiccmp.org> wrote: > Bill wrote: > > The guy that took me on the tour said that the wall behind the drum had to > be specially reinforced as if the drum exited the reinforced cabinet due to > some kind of failure while at speed, it would have gone through any > conventional wall like it was made of paper, and another wall which was the > side of the building, and would have fallen 6 floors to the ground below, > which obviously would have been disastrous. > > Apparently if there was a failure, due to the direction the drum rotated > it'd come out the back of the cabinet rather than the front. I was also > told that the drum cabinet had special mounting that was a large structure > of steel beams in the mezzanine level beneath the datacenter that connected > the mounts to the main support beams for the building, because the > gyroscopic effects of the drum would have torn out anything else. > > The mounts had to be inspected every six months to look for cracks or any > other sign of stress-induced problems. > > -Rick > A computer that literally required a specifically steel-reinforced building in order to operate. Now that's what you call Old Iron. Sellam
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
And on the humble Univac 418 we had the FH330. I have a picture of them somewhere On April 15, 2024 1:47:01 p.m. EDT, Van Snyder via cctalk wrote: >On Mon, 2024-04-15 at 09:25 -0400, Paul Koning via cctalk wrote: >> Are drums usually word addressable? That doesn't seem necessary, not unless >> you use them as main memory. > >Univac FH432, FH880, and FH1782 were word-addressable "flying head" >drums, usually used for swap, on 1100-series and maybe 1219 as well. > >
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
On Mon, 2024-04-15 at 09:25 -0400, Paul Koning via cctalk wrote: > Are drums usually word addressable? That doesn't seem necessary, not unless > you use them as main memory. Univac FH432, FH880, and FH1782 were word-addressable "flying head" drums, usually used for swap, on 1100-series and maybe 1219 as well.
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
Bill wrote: > I'll bet the source was talking about large contemporary storage > > units that looked like drums or may have been called "drums" but > were not actual 50's drum memory with tubes and such. There was no > > rotating drum storage, the media rotates in the PDP era. > Take a look at any pdp 11 peripheral handbook, there would be drum > memory > there if it was an official product. Remember that there was a very active third-party peripheral device market for the PDP-11 series. Could be that someone offered a head-per-track drum store that the person that made the update to Wikipedia may have spied. On a somewhat related note, many years ago, sometime in the late 1970's to perhaps no later than '81, I toured a local (Portland, OR) timesharing service that was called "Information Sciences, Inc.". They had their datacenter in a building in downtown Portland. They offered timeshare services on a well-built-out and heavily-modified DEC PDP-10 (KA-10). The machine had a bunch of add-on solid-state memory boxes, as well as a real drum memory. The drum memory unit was quite large, a box about 5 feet wide, 4 feet tall, and probably about 3-4 feet deep. The controller for the drum was another box that was about the same size as one of the memory boxes, and was cool because it had a bank of lamps at the top of the cabinet that showed the activity of the drum. It was flickering like crazy, as it was during prime-time that I was there, and they had about 180 simultaneous users on the system at the time. I was told that the drum was a head-per-track unit, and revolved at 8,000 RPM. The KA-10 had been modified to support virtual memory using a pager box of some sort, and the drum was used to support high-speed paging and swapping. The drum was kind of ominous, as you could sense the kinetic energy that was just waiting to be released if a bearing failed catastrophically. It had this low frequency resonance that felt as if it permeated the entire data center. The guy that took me on the tour said that the wall behind the drum had to be specially reinforced as if the drum exited the reinforced cabinet due to some kind of failure while at speed, it would have gone through any conventional wall like it was made of paper, and another wall which was the side of the building, and would have fallen 6 floors to the ground below, which obviously would have been disastrous. Apparently if there was a failure, due to the direction the drum rotated it'd come out the back of the cabinet rather than the front. I was also told that the drum cabinet had special mounting that was a large structure of steel beams in the mezzanine level beneath the datacenter that connected the mounts to the main support beams for the building, because the gyroscopic effects of the drum would have torn out anything else. The mounts had to be inspected every six months to look for cracks or any other sign of stress-induced problems. I don't know who made the drum unit, as I didn't see any tag on it, but the cabinetry was colored a significantly darker shade of blue than the DEC boxes were, which tells me that it was probably a third-party device. I was also told that the drum had its own UPS and genset, because it would be "bad" if it ever shut down in an unplanned way. Apparently there was a procedure that involved slowing down the drum revolution in a stepwise fashion. This apparently took something like 2 1/2 hours to perform, and was orchestrated by the controller. I never heard what "bad" meant in the context of the drum powering down in an unplanned fashion, but the tone of voice of the guy explaining it made it clear that it was something to be avoided at all cost. This was the first time that I'd ever seen a PDP-10, notably a KA-10, and I absolutely fell in love with the console of the machine. It's my favorite classic blinkenlights console. -Rick
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
I recall around 1980, the "A" machine at Purdue University Electrical Engineering, a PDP-11/70 running Version 7 Unix had a RS04 drum drive used for swap. It was getting long in the tooth and when a power failure occurred, someone would have to get a wrench to help spin it up as the head lubricant was no longer as good as it once was... --tom On 4/15/24 11:33, Mike Katz via cctalk wrote: There was drum storage for the early PDP-8 the "Straight 8", PDP-9 and PDP-10. Each drum stored 32,768 words. Up to 8 of them could be connected for a total storage of 262,144 words of storage. IBM made a 5BM drum storage unit that was the side of a small refrigerator: The RAMAC's disk storage unit, the IBM 350, weighed over a ton, had to be moved around with forklifts, and was delivered via large cargo airplanes. It stored approximately 5MB of data: *five million 8-bit characters on fifty 24-inch-diameter disks*, a form of drum memory. On 4/15/2024 11:06 AM, Douglas Taylor via cctalk wrote: At the VFC East just a few days ago a young man came up to me, I had a PDP11/53 on display, and showed me pictures of his 11/45 and PDP-8 that he had just acquired and needed to learn about. It was impressive, he said the 11/45 was missing the memory boards. If he shows up here on the list please help him. To me, it look like he had stumbled into a Unicorn. Doug On 4/13/2024 5:26 PM, Christopher Zach via cctalk wrote: Was reading the Wikipedia article on Drum memories: https://en.wikipedia.org/wiki/Drum_memory#External_links And came across this tidbit. As late as 1980, PDP-11/45 machines using magnetic core main memory and drums for swapping were still in use at many of the original UNIX sites. Any thoughts on what they are talking about? I could see running the RS03/RS04 on a 11/45 with the dual Unibus configured so the RS03's talk to memory directly instead of the Unibus, but that's not quite the same as true drum memory. Closest thing I remember was the DF32 on a pdp8 which could be addressed by word as opposed to track/sector. Thoughts? C
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
On Mon, Apr 15, 2024 at 8:00 AM Bill Gunshannon via cctalk < cctalk@classiccmp.org> wrote: > > > A README in the root of 2.11 says: > > The following manual pages are NOT in 2.10BSD but ARE in 4.3BSD: > > and one of them is drum.4 > > so, I guess we need to look at a 4.3BSD system to find out what > drum they are talking about. I have a feeling this is a device > that works on the VAX but is actually not found on any PDP-11. > Why it automatically makes the device node is beyond me. > Likely because MAKEDEV was copied over from 4.3's version. We've grown spoiled with dynamic device population, but even 4.4BSD had static creation with MAKEDEV. This is just the paging device for the system. It has nothing to do with old-school hardware, apart from the name. It's a logical device that spills over all the configured swap partitions / disks. The PDP-11 2.*BSD never had /dev/drum that was functional. Warner
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
There were also spinning disk "drum" memories. I used to have one (or most of one at least). Sellam
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
There was drum storage for the early PDP-8 the "Straight 8", PDP-9 and PDP-10. Each drum stored 32,768 words. Up to 8 of them could be connected for a total storage of 262,144 words of storage. IBM made a 5BM drum storage unit that was the side of a small refrigerator: The RAMAC's disk storage unit, the IBM 350, weighed over a ton, had to be moved around with forklifts, and was delivered via large cargo airplanes. It stored approximately 5MB of data: *five million 8-bit characters on fifty 24-inch-diameter disks*, a form of drum memory. On 4/15/2024 11:06 AM, Douglas Taylor via cctalk wrote: At the VFC East just a few days ago a young man came up to me, I had a PDP11/53 on display, and showed me pictures of his 11/45 and PDP-8 that he had just acquired and needed to learn about. It was impressive, he said the 11/45 was missing the memory boards. If he shows up here on the list please help him. To me, it look like he had stumbled into a Unicorn. Doug On 4/13/2024 5:26 PM, Christopher Zach via cctalk wrote: Was reading the Wikipedia article on Drum memories: https://en.wikipedia.org/wiki/Drum_memory#External_links And came across this tidbit. As late as 1980, PDP-11/45 machines using magnetic core main memory and drums for swapping were still in use at many of the original UNIX sites. Any thoughts on what they are talking about? I could see running the RS03/RS04 on a 11/45 with the dual Unibus configured so the RS03's talk to memory directly instead of the Unibus, but that's not quite the same as true drum memory. Closest thing I remember was the DF32 on a pdp8 which could be addressed by word as opposed to track/sector. Thoughts? C
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
At the VFC East just a few days ago a young man came up to me, I had a PDP11/53 on display, and showed me pictures of his 11/45 and PDP-8 that he had just acquired and needed to learn about. It was impressive, he said the 11/45 was missing the memory boards. If he shows up here on the list please help him. To me, it look like he had stumbled into a Unicorn. Doug On 4/13/2024 5:26 PM, Christopher Zach via cctalk wrote: Was reading the Wikipedia article on Drum memories: https://en.wikipedia.org/wiki/Drum_memory#External_links And came across this tidbit. As late as 1980, PDP-11/45 machines using magnetic core main memory and drums for swapping were still in use at many of the original UNIX sites. Any thoughts on what they are talking about? I could see running the RS03/RS04 on a 11/45 with the dual Unibus configured so the RS03's talk to memory directly instead of the Unibus, but that's not quite the same as true drum memory. Closest thing I remember was the DF32 on a pdp8 which could be addressed by word as opposed to track/sector. Thoughts? C
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
On Mon, Apr 15, 2024 at 12:53 AM Christopher Zach via cctalk < cctalk@classiccmp.org> wrote: > > > As late as 1980, PDP-11/45 machines using magnetic core main memory > and drums for swapping were still in use at many of the original UNIX > sites. > > Any thoughts on what they are talking about? I could see running the > RS03/RS04 on a 11/45 with the dual Unibus configured so the RS03's talk > to memory directly instead of the Unibus, but that's not quite the same > as true drum memory. > > I'll bet the source was talking about large contemporary storage units that looked like drums or may have been called "drums" but were not actual 50's drum memory with tubes and such. There was no rotating drum storage, the media rotates in the PDP era. Take a look at any pdp 11 peripheral handbook, there would be drum memory there if it was an official product. Bill
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
A README in the root of 2.11 says: The following manual pages are NOT in 2.10BSD but ARE in 4.3BSD: and one of them is drum.4 so, I guess we need to look at a 4.3BSD system to find out what drum they are talking about. I have a feeling this is a device that works on the VAX but is actually not found on any PDP-11. Why it automatically makes the device node is beyond me. bill
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
On 4/15/2024 9:45 AM, Jonathan Chapman via cctalk wrote: Well, I can submit a correction, but does anyone remember /dev/drum? I don't recall that in V6m or V7 Unix, I guess I could fire one of them up and see There's at least references to /dev/drum in 2.11BSD, I forget if it was in the docs or actually important stuff in the source. I don't have my PDP-11/83 set up at the moment to check! I just fired up my running copy and while there is a /dev/drum device there does not appear to be any mention of it anywhere in the file system, not even in the sources. Not sure what that means. Have to try a deeper search but that will take some time to run. bill
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
> Well, I can submit a correction, but does anyone remember /dev/drum? I > don't recall that in V6m or V7 Unix, I guess I could fire one of them up > and see There's at least references to /dev/drum in 2.11BSD, I forget if it was in the docs or actually important stuff in the source. I don't have my PDP-11/83 set up at the moment to check! Thanks, Jonathan
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
> On Apr 13, 2024, at 5:26 PM, Christopher Zach via cctalk > wrote: > > Was reading the Wikipedia article on Drum memories: > > https://en.wikipedia.org/wiki/Drum_memory#External_links I noticed the question was asked (but not answered): what is the largest storage capacity found in drums? I commented that it's at least 512k 27-bit words, which is the size of the Electrologica X8 drum, circa 1970. That reminded me the TU Eindhoven replaced their X8 by a Burroughs 6700 system, which also had a drum. I remember a cube about a meter wide. But I don't remember its capacity and can't find anything on Bitsavers that even mentions drums on any Burroughs mainframe. Does anyone know? paul
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
> On Apr 13, 2024, at 5:26 PM, Christopher Zach via cctalk > wrote: > > Was reading the Wikipedia article on Drum memories: > > https://en.wikipedia.org/wiki/Drum_memory#External_links > > And came across this tidbit. > > As late as 1980, PDP-11/45 machines using magnetic core main memory and drums > for swapping were still in use at many of the original UNIX sites. > > Any thoughts on what they are talking about? I could see running the > RS03/RS04 on a 11/45 with the dual Unibus configured so the RS03's talk to > memory directly instead of the Unibus, but that's not quite the same as true > drum memory. > > Closest thing I remember was the DF32 on a pdp8 which could be addressed by > word as opposed to track/sector. > > Thoughts? > C I don't know of any drums on PDP-11 systems. RS03/04 are of course fixed head disks, as are the earlier RF11 and RC11/RS64. All these are functional analogs of drums in that they have no seek time. Are drums usually word addressable? That doesn't seem necessary, not unless you use them as main memory. Even the early ARMAC (1956-ish) which uses a drum for main memory doesn't really need it to be word-addressable because it had a one-track buffer memory (think of it as an early cache). If you want word-addressable, the RF11 will do that. Not the RC11, it has 32 word sectors. paul
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
This uncited claim was introduced 15 years ago, along with the commit comment "Hey, I saw drums (and core memory!) on PDP 11/45 hardware running UNIX v6 (pre-BSD) in 1980 ... " So, someone anonymous saw some once, somewhere, and promoted this to "many sites." Well, I can submit a correction, but does anyone remember /dev/drum? I don't recall that in V6m or V7 Unix, I guess I could fire one of them up and see Speaking of which I should make a copy of those disk packs for SIMH. They are genned for a dual RL01 11/34 system and while I recall they also worked on an 11/23 I don't have a pair of RL01's anymore (just an RL02 I can re-jumper to read RL01 packs but NEVER WRITE THEM)
[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....
On Sat, 13 Apr 2024 17:26:31 -0400 Christopher Zach via cctalk wrote: > Was reading the Wikipedia article on Drum memories: > > https://en.wikipedia.org/wiki/Drum_memory#External_links > > And came across this tidbit. > > As late as 1980, PDP-11/45 machines using magnetic core main memory > and drums for swapping were still in use at many of the original UNIX > sites. This uncited claim was introduced 15 years ago, along with the commit comment "Hey, I saw drums (and core memory!) on PDP 11/45 hardware running UNIX v6 (pre-BSD) in 1980 ... " So, someone anonymous saw some once, somewhere, and promoted this to "many sites."
