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

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

Core memory yes - Drum memory I dont think so. Rod Smallwood  (Digital Equipment Corporation 1975 - 1985) On 15/04/2024 08:06, Paul Flo Williams via cctalk wrote:

Oh yeah, the pdp11 world had a DF32 like thing with the RF11. Totally forgot about that one. C

On Mon, 2024-04-15 at 09:25 -0400, Paul Koning via cctalk wrote: Univac FH432, FH880, and FH1782 were word-addressable "flying head" drums, usually used for swap, on 1100-series and maybe 1219 as well.

Bill wrote: 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

On 15/04/2024 15:00, Bill Degnan via cctalk wrote: There is a mention of drum memory storage in the PDP-11 Memory Management handbook: http://www.bitsavers.org/www.computer.museum.uq.edu.au/pdf/DEC-11-HGKTCB-D%… page 21 I imagine that any "drum like storage" attached to an 11/45 would be fixed head disk storage rather than actual drum memory. After all, from a digital perspective they're identical. Josh

For that matter, there are a lot of DEC products not seen in any Handbook. If you want to see everything that was produced by DEC, check the Option/Module list. To pick an example, the typesetting products were certainly official DEC products, not CSS, though admittedly low volume. But you won't find the PA611, or the VT61/t, or the VT71 or VT20, in any peripheral or other "handbook". paul

There were also spinning disk "drum" memories. I used to have one (or most of one at least). Sellam

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

On Mon, 15 Apr 2024, Tom Gardner via cctalk wrote: 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 to Disneyland, Frank Sinatra offered to take Mrs. Khruschev to Disneyland, but that didn't happen. The secret service tried to make it up to him by arranging a tour of an IBM plant in San Jose where the RAMACs were being built. I have a RAMAC platter! It was acquired sometime before 1983 by Wilson Price (one of my cow- orkers) and we used it for decades to convince beginning computer students that there has been progress on size and capacity of disks. It is much too damaged to be restorable. So, I made a patio table out of it. It already has a specific bequest? in my will. -- Grumpy Ol' Fred cisin(a)xenosoft.com