>
>Subject: Re: PC floppy cable twists...
> From: "Chuck Guzis" <cclist at sydex.com>
> Date: Thu, 20 Oct 2005 14:53:41 -0700
> To: cctalk at classiccmp.org
>
>On 10/20/2005 at 4:14 PM Michael B. Brutman wrote:
>
>>With all of those pins on the interface, why wouldn't the motors be
>>independently controlled? That seems like a waste on any system, never
>>mind the wear and tear on the drives & inserted floppies.
>
>But there really aren't any unused pins. Remember that all of the
>odd-numbered pins are grounded, so that leaves only 16 for signals. Pin 2
>was originally reserved for "reduced write current" signalling (or "density
>select'). Pin 4 was for "Head load" and was a spare only on some drives
>that didn't have that feature and pin 34 was used for disk change/ready.
>There really aren't any spares.
>
>Besides, with a "head load" facility, who needed to control the motors
>individually? But the PC didn't use a drive with a head load facility...
>
>Cheers,
>Chuck
Once upon a time drive need time to spin up before you loaded the head
and read it. As drives improved that time shortend and the motors went
to brushless where relibility didn't degrade with stops and starts
(brush motors this is a relability/wear issue). So having seperate motor
enables allowed one to spin the drives and then allow a 10sec (or longer)
timeout after last access before they would stop.
Allison
>
>Subject: Re: RL01 drive select plug and power supply questions
> From: David Betz <dbetz at xlisper.mv.com>
> Date: Thu, 20 Oct 2005 18:26:02 -0400
> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>Thanks for your reply. I guess I'm okay with power even if I leave in
>the DHV11 as it seems my BA11-N has been upgraded to a H7861 power
Unless you need the IO I'd pull it anyway. The system will run cooler
and I doubt you have need for the lines. DHV11 is a MUX and you need
the chassis kit to break out all the serial lines. Most OSs for PDP11
don't use it (system build time option) and the DLV11J is easier to use
and program. The DHV11 cannot be used for a console either.
>supply already. I'll consider getting an RQDX3 instead of the RQDX1.
>Do you know if it uses the same cables to connect it with its drives?
All the RQDXn controlers use the same cables. You will need the RQDX
breakout board (either out of the BA23 or M9058 out of the BA123) to take
the 50pin wide RQDXn to drive cables.
>Actually, the only cable I have is to connect the RQDX1 to an RX50
>floppy drive. I'll need a cable to connect it to a hard drive at some
>point. It seems that the RQDX3 cards are easier to come by than the
>cables. I've seen many cards on eBay but never any cables.
The cables are nothing special. Your missing the intermediate board
that gors from the 50pin RQDXn to the 43pin that RX50 or RX33 uses
and the 34/26pin comblo that common MFM hard disks used.
Sounds like you have something like my 11/73. Mine is
4mb ram, RL02, RX33, (2)RD52 and RX02, serial is DLV11j.
I run unix V6, Rt11XM and XXDP.
Allison
>On Oct 20, 2005, at 6:19 PM, Allison wrote:
>
>>>
>>> Subject: RL01 drive select plug and power supply questions
>>> From: David Betz <dbetz at xlisper.mv.com>
>>> Date: Thu, 20 Oct 2005 17:28:56 -0400
>>> To: "General Discussion: On-Topic and Off-Topic Posts"
>>> <cctalk at classiccmp.org>
>>>
>>> Does anyone have a spare RL01 drive select plug for drive "0"? I
>>> recently acquired an RL01 drive (thanks Lyle Bickly and Jon Miles!)
>>> but it's missing its drive select plug. This is one of the four
>>> lights on the front of the drive that has the number "0" printed on
>>> it for drive 0. Does anyone have one they're willing to part with?
>>>
>>> Also, the PDP-11/73 that I acquired is in a BA11-NC box. Does anyone
>>> know how much power the power supply in this box can supply? There is
>>> a list of the cards in the box and the power each one consumes and
>>> I've inserted an additional card (an RQDX1 controller) that draws
>>> 6.4A at 5V and I'm not sure that the power supply can handle it. That
>>> would bring the total to 26.9A at 5V where the original total was
>>> 22.3A. I could remove a DHV11 card that draws 4.3A to bring the total
>>> down to 22.6A if necessary. What is save with this power supply?
>>>
>>> Thanks,
>>> David
>>>
>>
>> BA-11N +5 at 22A +12 at 11A max assumes H9273 mackplane and H786 PS
>>
>> I have a system that I subbed in a H7861 to the BA11N that PS is
>> same size
>> and form factor but +5 at 36A and +12 at 5A (typically found in BA11S).
>> As most
>> newer boards had a greater need for +5 than +12.
>>
>> If you don't need the serial lines then pull the DHV11. I've found
>> running the supply right at the limit was not the best for
>> reliability.
>>
>> Also the RQDX1 was not a very good version unless it was upgraded to
>> RQDX2. the reason is it didn't support RX33, and the largest disk
>> if memory serves for RQDX1 was RD52 (30mb quantum D540). RQDX2
>> supported
>> the RD53(70mb) and RD54 (150mb). The RQDX3 supported more drives and
>> is a bit lighter in current draw (RD31 and 32 plus RX33).
>>
>> ALSO the RQDX1 MUST BE LAST ON THE BUS. Many of the RQDX1 controllers
>> lacked GRANT pass down.
>>
>>
>> Allison
>>
>
>Subject: RL01 drive select plug and power supply questions
> From: David Betz <dbetz at xlisper.mv.com>
> Date: Thu, 20 Oct 2005 17:28:56 -0400
> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>Does anyone have a spare RL01 drive select plug for drive "0"? I
>recently acquired an RL01 drive (thanks Lyle Bickly and Jon Miles!)
>but it's missing its drive select plug. This is one of the four
>lights on the front of the drive that has the number "0" printed on
>it for drive 0. Does anyone have one they're willing to part with?
>
>Also, the PDP-11/73 that I acquired is in a BA11-NC box. Does anyone
>know how much power the power supply in this box can supply? There is
>a list of the cards in the box and the power each one consumes and
>I've inserted an additional card (an RQDX1 controller) that draws
>6.4A at 5V and I'm not sure that the power supply can handle it. That
>would bring the total to 26.9A at 5V where the original total was
>22.3A. I could remove a DHV11 card that draws 4.3A to bring the total
>down to 22.6A if necessary. What is save with this power supply?
>
>Thanks,
>David
BA-11N +5 at 22A +12 at 11A max assumes H9273 mackplane and H786 PS
I have a system that I subbed in a H7861 to the BA11N that PS is same size
and form factor but +5 at 36A and +12 at 5A (typically found in BA11S). As most
newer boards had a greater need for +5 than +12.
If you don't need the serial lines then pull the DHV11. I've found
running the supply right at the limit was not the best for reliability.
Also the RQDX1 was not a very good version unless it was upgraded to
RQDX2. the reason is it didn't support RX33, and the largest disk
if memory serves for RQDX1 was RD52 (30mb quantum D540). RQDX2 supported
the RD53(70mb) and RD54 (150mb). The RQDX3 supported more drives and
is a bit lighter in current draw (RD31 and 32 plus RX33).
ALSO the RQDX1 MUST BE LAST ON THE BUS. Many of the RQDX1 controllers
lacked GRANT pass down.
Allison
> Now that I have an apparently functioning PDP-8/A with 16K of core, and
> (hopefully soon) a working RL02, I am wondering what operating system
> would be appropriate. Currently I don't have any other input device aside
> from the programmer's panel and the keyboard, so naturally I need something
> that can be booted from an RL02...
>
> Any recommendations? Will software written for, say, an 8/E or 8/I run on
> an 8/A without patching?
>
>Could I run OS/8? TSS/8? Many years ago I used to have access to a TTY
>timeshare d to an 8/E running Edusystem 50 (TSS/8) and would like
>that "feel" again...
The 8/A was compatible with the earlier machines so software should work
unless they were requiring an option which isn't on the 8/A. OS/8
is your best bet. TSS/8 won't work with an RL drive.
For multi user operating systems the only one that will run on your
hardware is Multos-8. The version that has been recovered doesn't seem
to operate well though.
... discussion about this on another list got me curious - what *was*
the point of that cable twist in a (IBM clone) PC floppy cable, when
every other system on the planet was using straight-through cables?
1) Great, it means both drives in a system can be jumpered for the same
ID - but someone's still got to go in and jumper/modify the last drive
in the chain so that it's terminated, so it's not like the twist
eliminates messing around with jumpers.
2) when the twist was introduced, there were presumably no clone
machines around (it was there from day 1 IIRC) - and wouldn't the
addition of a second floppy drive to an IBM machine have been a field
service call anyway? So it's not like it was the general public changing
jumpers, but a trained engineer...
3) IBM seemed to use a very small range of drives in the PC / XT / 286
days, so it's not like there'd be a million jumper combinations to
figure out. If a customer tried to add their own drive rather than
buying through IBM, surely IBM couldn't care less if they struggled to
figure the drive jumpers on their 'non-standard' unit out?
It's got me curious as it seems like a hack that doesn't completely
solve any kind of problem whilst introducing a difference between IBM
and the rest of the industry.
cheers
Jules
For the longest time I was stumped about how to get four drives onto a
PC 5150. The BIOS supports it, but looking at the cable it just
shouldn't work. There was the twist to control drive select and the one
motor line - that's not enough to control four drives.
I started kicking myself really hard when I rememberd that the other two
drives had to go on the external cable, which has it's own motor and
drive select line ...
Still, mapping out the PC floppy cable compared to other systems was
interesting. Even compared to an AT it is different. The AT supports a
high density signal line on a previously unused pin. The other systems
looked like they had independent drive select lines, but as somebody
else pointed out, the motors all ran at the same time.
With all of those pins on the interface, why wouldn't the motors be
independently controlled? That seems like a waste on any system, never
mind the wear and tear on the drives & inserted floppies.
Mike
Dear Classic Computers,
I regret that my EE knowledge was never deep and is
a little rusty now. I am refurbishing some old PC
boards and wanted to replace a few of the LED which
had become damaged or broken off. Here is my lame
question, how do I correctly pick replacement LEDs?
I know colors, and size, but how do I make certain
that I have picked correct wattage, etc.?
If some one with more experience could provide a
few sentences of guidance I would be grateful. I
can even put a Tektronix scope on it and take
measurements if necessary.
Bradley Slavik
Does anyone have a spare RL01 drive select plug for drive "0"? I
recently acquired an RL01 drive (thanks Lyle Bickly and Jon Miles!)
but it's missing its drive select plug. This is one of the four
lights on the front of the drive that has the number "0" printed on
it for drive 0. Does anyone have one they're willing to part with?
Also, the PDP-11/73 that I acquired is in a BA11-NC box. Does anyone
know how much power the power supply in this box can supply? There is
a list of the cards in the box and the power each one consumes and
I've inserted an additional card (an RQDX1 controller) that draws
6.4A at 5V and I'm not sure that the power supply can handle it. That
would bring the total to 26.9A at 5V where the original total was
22.3A. I could remove a DHV11 card that draws 4.3A to bring the total
down to 22.6A if necessary. What is save with this power supply?
Thanks,
David
Now that I have an apparently functioning PDP-8/A with 16K of core, and (hopefully soon) a working RL02, I am wondering what operating system would be appropriate. Currently I don't have any other input device aside from the programmer's panel and the keyboard, so naturally I need something that can be booted from an RL02...
Any recommendations? Will software written for, say, an 8/E or 8/I run on an 8/A without patching?
Could I run OS/8? TSS/8? Many years ago I used to have access to a TTY timeshared to an 8/E running Edusystem 50 (TSS/8) and would like that "feel" again...
thanks
Charles
