RQDX3/RD31/RX50 jumpers
Hi Is the correct setting: 1. DS1 on the RD31 and the RX50's move up to DU1 and DU2. 2. DS3 on the RD31 and the RX50's are DU0 and DU1 I've tried both and it still tries to access the RD31 and the RX50 at the same time. Its on a standrd BA23 R
RE: Racking a PDP-11/24
> -Original Message- > From: pbir...@gmail.com > Sent: 26 February 2022 20:22 > To: r...@jarratt.me.uk; 'General Discussion: On-Topic and Off-Topic Posts' > > Subject: RE: Racking a PDP-11/24 > > A top-mount corporate cabinet looks like this: > http://www.cosam.org/images/pdp11-23/front2.jpg The "DECDatasystem" > front-bar in the photo is over the 1U strengthener that braces the upper > portion of the rack ... since there is no brace at the top (as yours has). > Your cabinet will work fine; in my experience RL02's are always tight and > fiddly any place but the top-spot. > > The "play" is because those immense-head screws are the pivot-points that > allow the chassis to be pivoted up 90 degrees (when the slides are extended) > in order to more easily access the underside of the backplane. They are > intentionally slightly loose in order for the pivot to work. You really don't > need, or want, to play with those screws. Ah! Thanks for that advice. > > -Original Message- > From: Rob Jarratt > Sent: Saturday, February 26, 2022 3:04 PM > To: pbir...@gmail.com; r...@jarratt.me.uk; 'General Discussion: On-Topic > and Off-Topic Posts' > Subject: RE: Racking a PDP-11/24 > > Thank you for the reply. > > > -Original Message- > > From: pbir...@gmail.com > > Sent: 26 February 2022 08:48 > > To: r...@jarratt.me.uk; 'Rob Jarratt' ; > 'General > > Discussion: On-Topic and Off-Topic Posts' > > Subject: RE: Racking a PDP-11/24 > > > > The conventional mounting for RL02 drives in a corporate cabinet puts > > one > at > > the top with the 6U CPU in the middle *but* that assumes that you have > > a corporate cabinet designed for that purpose -- in which case the top > > is missing so that the RL02 disk-pack can be directly accessed, and > > there is a 1U divider below the top RL02 that reinforces the rack (and > > in effect > replaces the > > 1U lip on your rack top). > > I saw something somewhere that suggested the RL02 should be at the top > with the disk accessible without pulling out the drive. I don't think the cabinet > I have was intended to do that, but I will have a closer look. > > > > > AFAIK you should be able to make your rack plan work; it's just the > > case that > > RL02 are always "top snug" (at least in my experience). Have you > > tried raising the 6U CPU as high as possible *before* tightening the > > bolts/screws on the mounting flanges on the slides (to the rack, not > > to the chassis)? > > There's usually ~1/8" of play there. From your photo perhaps you have > > already done that as the CPU-front looks to be snug to the rack-top. > > If anything it looks as if your RL02 instead need to move down. > > > > I did try raising the CPU as high as possible. Will have another look to see > if the RL02s can be dropped a bit lower, but I don't think they can go lower > in terms of using lower slots, not unless I want to leave a gap and possible > interfere with the space at the bottom where there will be some cables I > think. I would like to avoid filing though! > > > I would start by moving the bottom RL02 down as far as possible, then > repeat > > with the second RL02. > > > > Your observation that there is "very little clearance between the CPU > > and the > > RL02 at the front but more at the back" suggests to me that you need > > to fiddle move with the front and /or rear mounting flange positioning > > on the various slides. Don't assume that wherever "gravity drops > > them" is going to > > be correct. > > > > If none of the suggested adjustments are working then I would consider > > getting out a rat-tail file and enlarging the slots on the mounting > flanges on > > the RL02 slides so as to let them drop a little lower (assuming that > > you have > > clearance at the bottom!). > > > > Regardless you shouldn't need to play with the slide-to-chassis > > attachment points -- those are always "just so" and not really free to > > fiddle with (no > > "slop"). > > There *is* a bit of play in the big black sheet that is screwed onto CPU > enclosure. > > > > > In my experience "racking" is a fiddling-time and clearances can be > *really* > > tight. But ... it can be done :->. Good Luck. > > > > -Original Message- > > From: cctalk On Behalf Of Rob Jarratt > > via cctalk > > Sent: Saturday, February 26, 2022 3:15 AM > > To: General Discussion: On-Topic and Off-Topic Posts > > > > Subject: Racking a PDP-11/24 > > > > I am wondering if I have racked my 11/24 correctly. > > > > As you can see here: > > https://robs-old-computers.com/2022/02/10/pdp-11-24-progress/ I have > > put the CPU at the top and the two RL02 drives underneath. > > > > The problem is that the CPU enclosure catches on the RL02 underneath. > > There is a bit of play in the mounting bracket: > > https://rjarratt.files.wordpress.com/2022/02/cpu-mounting-bracket.jpg. > > With a bit of manipulation I can get the CPU to slide in. However, I > > am wondering if I have racked it correctly?
Re: HP 9915A failed 8048
On 2022-02-26 16:21, Tony Duell via cctalk wrote: On Sat, Feb 26, 2022 at 5:19 PM js--- via cctalk wrote: As the chances of success are highly improbable, looks like I'm SOL on this particular motherboard. My bench is rather full at the moment and will be for a few more weeks... But if you get no other help and you can wait a bit, I believe one of my old EPROM programmers can read the 8048/8748 with the right adaptor, and the schematic of that is in the manual. I also have a working (I hope) HP9915. So I could have a go at making said adaptor, extracting the 8048 from my HP9915, and readng it out. You would then have to find somebody who could program the ROM image into an 8748. -tony If no one else steps up I have more that one programmer that can handle 8748, I probably have a few 8748s as well. Paul.
Re: Racking a PDP-11/24
I am not in the USA, but I am should be able to look for other screwdrivers here in the UK. I already have one quite big one, but I think it is still way too small for this purpose. How big is it? For ridiculously large flat-blade screws, look at "drag link socket"s. For just getting extreme amounts of torque, use a bit on a ratchet, rather than on a screwdriver handle.
Re: HP 9915A failed 8048
On Sat, Feb 26, 2022 at 5:19 PM js--- via cctalk wrote: > As the chances of success are highly > improbable, looks like I'm SOL on this > particular motherboard. My bench is rather full at the moment and will be for a few more weeks... But if you get no other help and you can wait a bit, I believe one of my old EPROM programmers can read the 8048/8748 with the right adaptor, and the schematic of that is in the manual. I also have a working (I hope) HP9915. So I could have a go at making said adaptor, extracting the 8048 from my HP9915, and readng it out. You would then have to find somebody who could program the ROM image into an 8748. -tony
RE: Racking a PDP-11/24
A top-mount corporate cabinet looks like this: http://www.cosam.org/images/pdp11-23/front2.jpg The "DECDatasystem" front-bar in the photo is over the 1U strengthener that braces the upper portion of the rack ... since there is no brace at the top (as yours has). Your cabinet will work fine; in my experience RL02's are always tight and fiddly any place but the top-spot. The "play" is because those immense-head screws are the pivot-points that allow the chassis to be pivoted up 90 degrees (when the slides are extended) in order to more easily access the underside of the backplane. They are intentionally slightly loose in order for the pivot to work. You really don't need, or want, to play with those screws. -Original Message- From: Rob Jarratt Sent: Saturday, February 26, 2022 3:04 PM To: pbir...@gmail.com; r...@jarratt.me.uk; 'General Discussion: On-Topic and Off-Topic Posts' Subject: RE: Racking a PDP-11/24 Thank you for the reply. > -Original Message- > From: pbir...@gmail.com > Sent: 26 February 2022 08:48 > To: r...@jarratt.me.uk; 'Rob Jarratt' ; 'General > Discussion: On-Topic and Off-Topic Posts' > Subject: RE: Racking a PDP-11/24 > > The conventional mounting for RL02 drives in a corporate cabinet puts > one at > the top with the 6U CPU in the middle *but* that assumes that you have > a corporate cabinet designed for that purpose -- in which case the top > is missing so that the RL02 disk-pack can be directly accessed, and > there is a 1U > divider below the top RL02 that reinforces the rack (and in effect replaces the > 1U lip on your rack top). I saw something somewhere that suggested the RL02 should be at the top with the disk accessible without pulling out the drive. I don't think the cabinet I have was intended to do that, but I will have a closer look. > > AFAIK you should be able to make your rack plan work; it's just the > case that > RL02 are always "top snug" (at least in my experience). Have you > tried raising > the 6U CPU as high as possible *before* tightening the bolts/screws on > the mounting flanges on the slides (to the rack, not to the chassis)? > There's usually ~1/8" of play there. From your photo perhaps you have > already done that as the CPU-front looks to be snug to the rack-top. > If anything it looks as if your RL02 instead need to move down. > I did try raising the CPU as high as possible. Will have another look to see if the RL02s can be dropped a bit lower, but I don't think they can go lower in terms of using lower slots, not unless I want to leave a gap and possible interfere with the space at the bottom where there will be some cables I think. I would like to avoid filing though! > I would start by moving the bottom RL02 down as far as possible, then repeat > with the second RL02. > > Your observation that there is "very little clearance between the CPU > and the > RL02 at the front but more at the back" suggests to me that you need > to fiddle move with the front and /or rear mounting flange positioning > on the various slides. Don't assume that wherever "gravity drops > them" is going to > be correct. > > If none of the suggested adjustments are working then I would consider > getting out a rat-tail file and enlarging the slots on the mounting flanges on > the RL02 slides so as to let them drop a little lower (assuming that > you have > clearance at the bottom!). > > Regardless you shouldn't need to play with the slide-to-chassis > attachment points -- those are always "just so" and not really free to > fiddle with (no > "slop"). There *is* a bit of play in the big black sheet that is screwed onto CPU enclosure. > > In my experience "racking" is a fiddling-time and clearances can be *really* > tight. But ... it can be done :->. Good Luck. > > -Original Message- > From: cctalk On Behalf Of Rob Jarratt > via cctalk > Sent: Saturday, February 26, 2022 3:15 AM > To: General Discussion: On-Topic and Off-Topic Posts > > Subject: Racking a PDP-11/24 > > I am wondering if I have racked my 11/24 correctly. > > As you can see here: > https://robs-old-computers.com/2022/02/10/pdp-11-24-progress/ I have > put the CPU at the top and the two RL02 drives underneath. > > The problem is that the CPU enclosure catches on the RL02 underneath. > There is a bit of play in the mounting bracket: > https://rjarratt.files.wordpress.com/2022/02/cpu-mounting-bracket.jpg. > With a bit of manipulation I can get the CPU to slide in. However, I > am wondering if I have racked it correctly? I don't think there is > room to move > the RL02s down and it would presumably leave a bit of a gap below the CPU. > There seems to be very little clearance between the CPU and the RL02 > at the > front but more at the back, but I am sure that the rails are mounted > horizontally. Is it just a matter of tightening the big screws that > hold the > mounting brackets to stop the play? If so I am not sure I have a big enough >
Re: Racking a PDP-11/24
> On Feb 26, 2022, at 3:05 PM, Rob Jarratt wrote: > >> ... >> Hardware stores can fix that. Or Brownells, where you can get really good >> screwdrivers that are less likely to damage screw heads than standard >> hardware store ones do. > > I am not in the USA, but I am should be able to look for other screwdrivers > here in the UK. I already have one quite big one, but I think it is still > way too small for this purpose. Brownell's is a gunsmith supply store, but the screwdrivers I was talking about are also known as "clockmaker's screwdrivers". Either way, they have hollow-ground hardened blades rather than flat-sided bevel tips, and they come in a range of withs as well as thickness. I use them for any situation where a good fit in the screw head is important. For oversized screwdrivers, the ones that are sold as pry bars can serve... paul
RE: Racking a PDP-11/24
> -Original Message- > From: Paul Koning > Sent: 26 February 2022 19:21 > To: r...@jarratt.me.uk; Robert Jarratt ; > cctalk@classiccmp.org > Subject: Re: Racking a PDP-11/24 > > > > > On Feb 26, 2022, at 3:14 AM, Rob Jarratt via cctalk > wrote: > > > > I am wondering if I have racked my 11/24 correctly. > > > > > > > > As you can see here: > > https://robs-old-computers.com/2022/02/10/pdp-11-24-progress/ I have > > put the CPU at the top and the two RL02 drives underneath. > > That seems fine. Others mentioned having them at the top of a low cabinet, > but the RL02s I used were in H960 (6 foot) racks, mid-level with stuff above > them. > > > The problem is that the CPU enclosure catches on the RL02 underneath. > > There is a bit of play in the mounting bracket: > > https://rjarratt.files.wordpress.com/2022/02/cpu-mounting-bracket.jpg. > > With a bit of manipulation I can get the CPU to slide in. However, I > > am wondering if I have racked it correctly? I don't think there is > > room to move the RL02s down and it would presumably leave a bit of a > > gap below the CPU. There seems to be very little clearance between the > > CPU and the RL02 at the front but more at the back, but I am sure that > > the rails are mounted horizontally. Is it just a matter of tightening > > the big screws that hold the mounting brackets to stop the play? If so > > I am not sure I have a big enough screwdriver! > > Hardware stores can fix that. Or Brownells, where you can get really good > screwdrivers that are less likely to damage screw heads than standard > hardware store ones do. I am not in the USA, but I am should be able to look for other screwdrivers here in the UK. I already have one quite big one, but I think it is still way too small for this purpose. > > Something I observed on my H960 that wasn't all that obvious at first: the > holes are NOT evenly spaced. If I remember right, they come in groups of > four where the spacing between groups is something like 1/8th of an inch > more than the spacing within groups. The consequence is that if you attach > your brackets using the wrong set of holes things may be 1/4 inch (or > whatever the delta is) closer than they were meant to be. > > paul
RE: Racking a PDP-11/24
Thank you for the reply. > -Original Message- > From: pbir...@gmail.com > Sent: 26 February 2022 08:48 > To: r...@jarratt.me.uk; 'Rob Jarratt' ; 'General > Discussion: On-Topic and Off-Topic Posts' > Subject: RE: Racking a PDP-11/24 > > The conventional mounting for RL02 drives in a corporate cabinet puts one at > the top with the 6U CPU in the middle *but* that assumes that you have a > corporate cabinet designed for that purpose -- in which case the top is > missing so that the RL02 disk-pack can be directly accessed, and there is a 1U > divider below the top RL02 that reinforces the rack (and in effect replaces the > 1U lip on your rack top). I saw something somewhere that suggested the RL02 should be at the top with the disk accessible without pulling out the drive. I don't think the cabinet I have was intended to do that, but I will have a closer look. > > AFAIK you should be able to make your rack plan work; it's just the case that > RL02 are always "top snug" (at least in my experience). Have you tried raising > the 6U CPU as high as possible *before* tightening the bolts/screws on the > mounting flanges on the slides (to the rack, not to the chassis)? > There's usually ~1/8" of play there. From your photo perhaps you have > already done that as the CPU-front looks to be snug to the rack-top. If > anything it looks as if your RL02 instead need to move down. > I did try raising the CPU as high as possible. Will have another look to see if the RL02s can be dropped a bit lower, but I don't think they can go lower in terms of using lower slots, not unless I want to leave a gap and possible interfere with the space at the bottom where there will be some cables I think. I would like to avoid filing though! > I would start by moving the bottom RL02 down as far as possible, then repeat > with the second RL02. > > Your observation that there is "very little clearance between the CPU and the > RL02 at the front but more at the back" suggests to me that you need to > fiddle move with the front and /or rear mounting flange positioning on the > various slides. Don't assume that wherever "gravity drops them" is going to > be correct. > > If none of the suggested adjustments are working then I would consider > getting out a rat-tail file and enlarging the slots on the mounting flanges on > the RL02 slides so as to let them drop a little lower (assuming that you have > clearance at the bottom!). > > Regardless you shouldn't need to play with the slide-to-chassis attachment > points -- those are always "just so" and not really free to fiddle with (no > "slop"). There *is* a bit of play in the big black sheet that is screwed onto CPU enclosure. > > In my experience "racking" is a fiddling-time and clearances can be *really* > tight. But ... it can be done :->. Good Luck. > > -Original Message- > From: cctalk On Behalf Of Rob Jarratt via > cctalk > Sent: Saturday, February 26, 2022 3:15 AM > To: General Discussion: On-Topic and Off-Topic Posts > > Subject: Racking a PDP-11/24 > > I am wondering if I have racked my 11/24 correctly. > > As you can see here: > https://robs-old-computers.com/2022/02/10/pdp-11-24-progress/ I have put > the CPU at the top and the two RL02 drives underneath. > > The problem is that the CPU enclosure catches on the RL02 underneath. > There is a bit of play in the mounting bracket: > https://rjarratt.files.wordpress.com/2022/02/cpu-mounting-bracket.jpg. > With a bit of manipulation I can get the CPU to slide in. However, I am > wondering if I have racked it correctly? I don't think there is room to move > the RL02s down and it would presumably leave a bit of a gap below the CPU. > There seems to be very little clearance between the CPU and the RL02 at the > front but more at the back, but I am sure that the rails are mounted > horizontally. Is it just a matter of tightening the big screws that hold the > mounting brackets to stop the play? If so I am not sure I have a big enough > screwdriver! > > Regards > > Rob
Re: HP 9915A failed 8048
On 2/26/22 12:15, js--- via cctalk wrote: On 2/25/2022 5:09 PM, Will Cooke via cctalk wrote: On 02/25/2022 2:23 PM Paul Berger via cctalk wrote: The 8048 is a mask programmed part, there is an EPROM version 8748. While the 8048 is mask programmed I believe that the contents of the ROM can be dumped. As Paul said, the 8048 is mask programmed. However, I agree it is readable. I "think" if you follow the "verify" step in the linked datasheet you can read from the rom. https://www.ceibo.com/eng/datasheets/Intel-8048-8049-8050-plcc-dip.pdf Will Thanks very much Paul, Will! From info gleaned from this webpage (especially the comments at bottom): http://www.mattmillman.com/projects/hveprom-project/an-easy-to-build-mcs-48-8748-8749-8741-8742-8048-8049-programmer-reader/ ... indeed looks like there is a chance the HP's 8048 could be read and possibly programmed into an alternate part. However, it's a daunting task in my case. I'd first have to build a 8048 programmer/reader shield for an Arduino, and then try to get my cracked 8048 successfully unsoldered from the HP 9915A motherboard, and then attempt to get consistent reads from it -- a special challenge due the crack. As the chances of success are highly improbable, looks like I'm SOL on this particular motherboard. Anyone have a HP 9915 they'd like to sell? Could the PROM be read by a running machine? Could someone who has one working read it and send you a copy of the image? bill
Re: Racking a PDP-11/24
> On Feb 26, 2022, at 3:14 AM, Rob Jarratt via cctalk > wrote: > > I am wondering if I have racked my 11/24 correctly. > > > > As you can see here: > https://robs-old-computers.com/2022/02/10/pdp-11-24-progress/ I have put the > CPU at the top and the two RL02 drives underneath. That seems fine. Others mentioned having them at the top of a low cabinet, but the RL02s I used were in H960 (6 foot) racks, mid-level with stuff above them. > The problem is that the CPU enclosure catches on the RL02 underneath. There > is a bit of play in the mounting bracket: > https://rjarratt.files.wordpress.com/2022/02/cpu-mounting-bracket.jpg. With > a bit of manipulation I can get the CPU to slide in. However, I am wondering > if I have racked it correctly? I don't think there is room to move the RL02s > down and it would presumably leave a bit of a gap below the CPU. There seems > to be very little clearance between the CPU and the RL02 at the front but > more at the back, but I am sure that the rails are mounted horizontally. Is > it just a matter of tightening the big screws that hold the mounting > brackets to stop the play? If so I am not sure I have a big enough > screwdriver! Hardware stores can fix that. Or Brownells, where you can get really good screwdrivers that are less likely to damage screw heads than standard hardware store ones do. Something I observed on my H960 that wasn't all that obvious at first: the holes are NOT evenly spaced. If I remember right, they come in groups of four where the spacing between groups is something like 1/8th of an inch more than the spacing within groups. The consequence is that if you attach your brackets using the wrong set of holes things may be 1/4 inch (or whatever the delta is) closer than they were meant to be. paul
Re: Is The M9312 Boot Module Essential?
> On Feb 26, 2022, at 2:19 AM, Noel Chiappa via cctalk > wrote: > So, either (console halt, or a HALT instruction) will cause the identical > response in the processor; see Section 4.10.3 "Halt Grant Requests": the CPU > sends HLT GRANT to the console, which returns SACK. As long as SACK is > asserted, the processor waits with its clock inhibited: Ah, interesting! I had no idea the console(s) used SACK to interact with the CPU in this way. That’s a useful tidbit to tuck away for future reference. > If there's a broken grant chain, then as you originally pointed out, the M9302 > will jam SACK on. The M8264 could not even be there, and nothing would be any > different. Same thing if the CPU asserts a grant in response to a now-removed > interrupt request: the M9302 will jam SACK on, etc, etc. Perhaps the intent was to always use a non-turnaround far side terminator in configurations with an M8264? cheers, —FritzM.
Re: HP 9915A failed 8048
On 2/25/2022 5:09 PM, Will Cooke via cctalk wrote: On 02/25/2022 2:23 PM Paul Berger via cctalk wrote: The 8048 is a mask programmed part, there is an EPROM version 8748. While the 8048 is mask programmed I believe that the contents of the ROM can be dumped. As Paul said, the 8048 is mask programmed. However, I agree it is readable. I "think" if you follow the "verify" step in the linked datasheet you can read from the rom. https://www.ceibo.com/eng/datasheets/Intel-8048-8049-8050-plcc-dip.pdf Will Thanks very much Paul, Will! From info gleaned from this webpage (especially the comments at bottom): http://www.mattmillman.com/projects/hveprom-project/an-easy-to-build-mcs-48-8748-8749-8741-8742-8048-8049-programmer-reader/ ... indeed looks like there is a chance the HP's 8048 could be read and possibly programmed into an alternate part. However, it's a daunting task in my case. I'd first have to build a 8048 programmer/reader shield for an Arduino, and then try to get my cracked 8048 successfully unsoldered from the HP 9915A motherboard, and then attempt to get consistent reads from it -- a special challenge due the crack. As the chances of success are highly improbable, looks like I'm SOL on this particular motherboard. Anyone have a HP 9915 they'd like to sell? - John Singleton
RE: Is The M9312 Boot Module Essential?
>> (I have yet to check and see if the KY11-LB asserts SACK if the CPU >> halts on its own accord - probably 'yes', but that's a project for tomorrow.) Yes, it does. I toggled in the following program: 5000 5200 776 0 (what, you all can't program a PDP-11 in octal? :-) and hit 'start' and the SACK light on the UA11 flashed out and came back on when the machine finally halted. So then I looked at CPU tech manual for the KD11-E, and the HALT instruction seems to act exactly like the console has requested a processor halt; it just sets the HLT RQST signal (see Section 4.5.5 "Operate Instructions"). So, either (console halt, or a HALT instruction) will cause the identical response in the processor; see Section 4.10.3 "Halt Grant Requests": the CPU sends HLT GRANT to the console, which returns SACK. As long as SACK is asserted, the processor waits with its clock inhibited: "The user can maintain the processor in this inactive state (Halted) indefinitely. When the HALT switch is released, the user's console releases BUS SACK L, and the processor continues operation" This text is obviously for the KY11-LA; the KY11-LB will operate identically: when the console releases SACK, the processor resumes operation. > From: Fritz Mueller >> when I powered the machine on, it turned out that something was >> asserting SACK when the machine was halted > That is quite interesting, and not what I would have expected! Yes, I was quite surprised; I didn't expect that either. Now that I know that the KY11-LB uses it to talk to the KD11, I can work around it, though. I'll have to write all this up to warn others about it. >> The thing that's puzzling me is that the M8264 seems to exactly >> replicate the functionality of the M9302, with an 'unused' bus grant >> being turned into a SACK. So I don't understand the point of the M8264. > I think the only difference would be that since the M8264 is timer > based, it doesn't need the intact end-to-end path required for > turnaround. So your bus won't lock even if you have a broken grant > chain or a poorly behaved or hung device eating grants. You are right about it being timer-based, but I'm not sure the conclusion follows, at least exactly as stated. If there's a broken grant chain, then as you originally pointed out, the M9302 will jam SACK on. The M8264 could not even be there, and nothing would be any different. Same thing if the CPU asserts a grant in response to a now-removed interrupt request: the M9302 will jam SACK on, etc, etc. I'm racking my brain to think up _any_ circumstance in which the M8264 will assert SACK. in which the M9302 wouldn't. Thinking it through, there has to be a grant, but it can't get to the M9302 (because otherwise it would do its thing), but that failure to get there can't be simply a broken grant chain (ditto). So some device has to be malfunctioning: not passing a grant along, but eating it. So either a hard-failed component in the grant-passing circuit, or some design flaw. (It can't be a glitch; it has to be a permanent thing which prevents passing the grant.) I suppose that's possible, but I can't see any othey way. Noel
Re: Racking a PDP-11/24
When I had a 11/24 it was in the wider cabinet (small panel to allow access to terminal cables and such) the cpu box was in the middle, with drive '1' on top. Regards, Ed -- Ik email, dus ik besta February 26, 2022 9:14 AM, "Rob Jarratt via cctalk" wrote: > I am wondering if I have racked my 11/24 correctly. > > As you can see here: > https://robs-old-computers.com/2022/02/10/pdp-11-24-progress I have put the > CPU at the top and the two RL02 drives underneath. > > The problem is that the CPU enclosure catches on the RL02 underneath. There > is a bit of play in the mounting bracket: > https://rjarratt.files.wordpress.com/2022/02/cpu-mounting-bracket.jpg. With > a bit of manipulation I can get the CPU to slide in. However, I am wondering > if I have racked it correctly? I don't think there is room to move the RL02s > down and it would presumably leave a bit of a gap below the CPU. There seems > to be very little clearance between the CPU and the RL02 at the front but > more at the back, but I am sure that the rails are mounted horizontally. Is > it just a matter of tightening the big screws that hold the mounting > brackets to stop the play? If so I am not sure I have a big enough > screwdriver! > > Regards > > Rob
RE: Racking a PDP-11/24
The conventional mounting for RL02 drives in a corporate cabinet puts one at the top with the 6U CPU in the middle *but* that assumes that you have a corporate cabinet designed for that purpose -- in which case the top is missing so that the RL02 disk-pack can be directly accessed, and there is a 1U divider below the top RL02 that reinforces the rack (and in effect replaces the 1U lip on your rack top). AFAIK you should be able to make your rack plan work; it's just the case that RL02 are always "top snug" (at least in my experience). Have you tried raising the 6U CPU as high as possible *before* tightening the bolts/screws on the mounting flanges on the slides (to the rack, not to the chassis)? There's usually ~1/8" of play there. From your photo perhaps you have already done that as the CPU-front looks to be snug to the rack-top. If anything it looks as if your RL02 instead need to move down. I would start by moving the bottom RL02 down as far as possible, then repeat with the second RL02. Your observation that there is "very little clearance between the CPU and the RL02 at the front but more at the back" suggests to me that you need to fiddle move with the front and /or rear mounting flange positioning on the various slides. Don't assume that wherever "gravity drops them" is going to be correct. If none of the suggested adjustments are working then I would consider getting out a rat-tail file and enlarging the slots on the mounting flanges on the RL02 slides so as to let them drop a little lower (assuming that you have clearance at the bottom!). Regardless you shouldn't need to play with the slide-to-chassis attachment points -- those are always "just so" and not really free to fiddle with (no "slop"). In my experience "racking" is a fiddling-time and clearances can be *really* tight. But ... it can be done :->. Good Luck. -Original Message- From: cctalk On Behalf Of Rob Jarratt via cctalk Sent: Saturday, February 26, 2022 3:15 AM To: General Discussion: On-Topic and Off-Topic Posts Subject: Racking a PDP-11/24 I am wondering if I have racked my 11/24 correctly. As you can see here: https://robs-old-computers.com/2022/02/10/pdp-11-24-progress/ I have put the CPU at the top and the two RL02 drives underneath. The problem is that the CPU enclosure catches on the RL02 underneath. There is a bit of play in the mounting bracket: https://rjarratt.files.wordpress.com/2022/02/cpu-mounting-bracket.jpg. With a bit of manipulation I can get the CPU to slide in. However, I am wondering if I have racked it correctly? I don't think there is room to move the RL02s down and it would presumably leave a bit of a gap below the CPU. There seems to be very little clearance between the CPU and the RL02 at the front but more at the back, but I am sure that the rails are mounted horizontally. Is it just a matter of tightening the big screws that hold the mounting brackets to stop the play? If so I am not sure I have a big enough screwdriver! Regards Rob
Racking a PDP-11/24
I am wondering if I have racked my 11/24 correctly. As you can see here: https://robs-old-computers.com/2022/02/10/pdp-11-24-progress/ I have put the CPU at the top and the two RL02 drives underneath. The problem is that the CPU enclosure catches on the RL02 underneath. There is a bit of play in the mounting bracket: https://rjarratt.files.wordpress.com/2022/02/cpu-mounting-bracket.jpg. With a bit of manipulation I can get the CPU to slide in. However, I am wondering if I have racked it correctly? I don't think there is room to move the RL02s down and it would presumably leave a bit of a gap below the CPU. There seems to be very little clearance between the CPU and the RL02 at the front but more at the back, but I am sure that the rails are mounted horizontally. Is it just a matter of tightening the big screws that hold the mounting brackets to stop the play? If so I am not sure I have a big enough screwdriver! Regards Rob
