Re: Adding floppy drives to my PDP-11?
On 04/13/2019 06:07 PM, Charles via cctalk wrote: > I have a PDP-11/23+ with two RL02's in a corporate cabinet but no > floppy drives. Also an RXV21 (M8029) card. > > My PDP-8/A has RX01 drives, and I was hoping just to run the cable > over to the -11 when I wanted to use floppies on it. > But after some searching, it appears that the RXV21 will only work > with an RX02 drive... > > Just wondering what my options are for hooking up any kind of floppy > drives. > I could sell the RXV21 and buy/trade for an RXV11 (M7946) instead, to > use with the RX01 in the other rack. > Or look for an RX02 that won't break the bank - but that won't fit in > the corporate cabinet. I do have another cabinet but it's got other > rack-mount gear in it at the moment. > What about smaller drives (RX50? RX33?)... can those be interfaced to > the 11/23+ Qbus? > Other thoughts? > thanks > Charles > > RX50, RX33, RX23 aall work with the RQDX2,3 controllers The boards and cables are fairly easy to find as they were used in microPDP11 and Qbus Microvax. Depending on the CPU they will be bootable (11/23+ I believe works). IF you lucky and can fine a quantum D540 or St225 you can have a hard disk as well. I have 11/23+ and 11/73 configured using that (rqdx2 in one and Rqdx3 in the other) and the breakout board. Many people skip over the MSCP controller for MFM hard disks as the hard drives are scarce, but floppies a Teac FG55GFR is the hot item as would be a RX50 or 1.44 3.5" floppy or all three as it can interface not less than two floppy drives. Allison
Re: Adding floppy drives to my PDP-11?
On 4/13/19 3:07 PM, Charles via cctalk wrote: > Other thoughts? find one of the dual-wide rx02 compatible floppy boards then you can use whatever kind of 8" drives you like and you can format media
Adding floppy drives to my PDP-11?
I have a PDP-11/23+ with two RL02's in a corporate cabinet but no floppy drives. Also an RXV21 (M8029) card. My PDP-8/A has RX01 drives, and I was hoping just to run the cable over to the -11 when I wanted to use floppies on it. But after some searching, it appears that the RXV21 will only work with an RX02 drive... Just wondering what my options are for hooking up any kind of floppy drives. I could sell the RXV21 and buy/trade for an RXV11 (M7946) instead, to use with the RX01 in the other rack. Or look for an RX02 that won't break the bank - but that won't fit in the corporate cabinet. I do have another cabinet but it's got other rack-mount gear in it at the moment. What about smaller drives (RX50? RX33?)... can those be interfaced to the 11/23+ Qbus? Other thoughts? thanks Charles
Re: Interesting article in Spectrum about IBM's System/360
On 04/13/2019 09:11 AM, Jay Jaeger via cctalk wrote: For example, the IBM 7010 was an IBM 1410 done up in 7000 series technology (and was a compatible super-set of the 1410 and, via a toggle switch, the 1401). It had no architectural relationship with the 7090/7094, nor did the 7070 or 7080, near as I can tell. Yes, the 14xx were character-based decimal machines. The 7070 was a word-based decimal machine aimed at the business market. The 709x were word-based binary machines. Jon
Re: Interesting article in Spectrum about IBM's System/360
On 4/12/2019 1:15 PM, Eric Smith via cctalk wrote: > The article says: > > Poughkeepsie’s engineers were close to completing work on a set of four >> computers known as the 8000s that were compatible with the 7000s. > > > AFAICT, that is totally wrong. The 8000 series was completely INCOMPATIBLE > with any of the 7000 series machines. In fact, most of the 7000 series > machines weren't even compatible with each other, though the 7040 and 7044 > had partial compatibility with the 7090 and 7094. > > There are some 8000 documents on Bitsavers so you can see for yourself. > http://bitsavers.trailing-edge.com/pdf/ibm/8000/ > Furthermore, like the 8000 series would have been, the 7000 series (and the 700 series, and the 1400 series, for that matter) was more of a series of *technology* rather than a series of compatible computers. The 7000 series used SMS ECL (current mode), at least in a lot of places, whereas the 1400 series were essentially RTL with some DTL sprinkled in on the 1410. For example, the IBM 7010 was an IBM 1410 done up in 7000 series technology (and was a compatible super-set of the 1410 and, via a toggle switch, the 1401). It had no architectural relationship with the 7090/7094, nor did the 7070 or 7080, near as I can tell. >From "The Genesis of the Mainframe" by Bob O. Evans (an extract from a longer memoirs document, which was not itself published, to my knowledge) https://researcher.watson.ibm.com/researcher/files/us-bbfinkel/bob_o_evans_mainframe.pdf "Flush with the success of the 1401 and the 1410 in process — I was not willing to abandon those winners to join the 8000 series plan, which did not sit right with me in the first place because the 8103, 8104, 8108 and the 8112 were architecturally incompatible and I was certain compatibility was fundamentally important." "By May 1961 I concluded the 8000 series would be a serious blunder, in part because of the lack of compatibility within the systems family. I did not buy Dr. Brooks’ arguments that recompilation would be acceptable to make it possible for the programming from all the dissimilar architectures of existing products to work effectively on the dissimilar architectures of the 8000 series. There were other important reasons to scrap the 8000 series plan including technology choice. Jerrier Haddad backed my decision; the 8000 Series plan was killed." My experience with a couple of magazine authors during my career tells me that many of them do not understand much of what they are writing, and errors like this 7000/8000 thing are common. Another half truth in the article reads: "The power of compatibility was demonstrated in the fall of 1960, when IBM introduced the more powerful 1410 to replace the 1401. Software and peripheral equipment for the 1401 worked with the newer machine. " That was only true to the extent that the 1410 included a 1401 compatibility mode switch, which literally changed the logic so that it became a (somewhat faster) 1401. In its normal 1410 position, it could not run 1401 programs, and vice/versa. JRJ
Re: Daisywhell typewriter emulating a TTY
On 4/12/19 10:00 PM, Dave Babcock via cctalk wrote: > Chuck, > > The Group Mark key was on later IBM 1620 Model 1 typewriters as well as > the Model 2 Selectrics. > > See: > https://www.dropbox.com/s/p2b1449zr6uqh6p/IBM_1620_Console_Typewriter.png?dl=0 > > > The flagged numeric blank was accidentally left out of the print sample > I made. > > Thanks, > Dave Thanks for that--I guess the CADETs that I fooled with way back when didn't have the group mark on the typewriter keyboard. Didn't matter much, as I mostly used cards, which allowed for some additional bit patterns (e.g. 821 for a record mark). I could see Dijstra's gripes with the machine--characters that you can only move, not test for or do arithmetic on. Characters that you could read, but not write. One thing that I never tried was to insert numeric blanks, record marks and group marks into the addition table and see what happened. Did you ever try that? Would you simply get an error stop if one of the non-numerics showed up in an addition? Egad, I haven't touched one of the things in something like 50 years and yet I can remember the numeric opcodes for much of it. It's amazing that the machines were as popular as they were. Ah, memories... --Chuck
