> On Wed, 7 Mar 2007, Chuck Guzis wrote:
>> I never *could* figure out where the card hopper was on the
>> Advantage.
>
> No hopper.
> You have to load the cards one at a time into the card drives on the
> front. It uses special 5.25" round cards (in a square jacket), and
> permits some magnetic data storage in the spaces between the punch
> holes.
Those early 5.25" punched cards don't have the best data density, but
on the upside they beat the Apple cards (1-bit per card).
As an added feature, they come pre-punched so you don't need to mess
with them.
All "ones", though.
>Subject: Re: tools / test gear / components in the US?
>>
>> Out of interest, whereabout in the US is good (mail order) for getting hold of
>> tools / test gear and components? There's only a Rat Shack in town here, which
>> as everyone knows is utterly useless for absolutely anything :(
Digikey is one,
Mouser,
JDRmicrodevices
Jameco
I've used all of them and some others at one time or another. Ratshack
used to have Allied electonics (big supplier) but, that may have gone away.
Allison
One poster mentioned the plasma drivers keeping the array below the threshold where they would glow.
TI used to make a pair of drivers to control a plasma display. SN55500 and SN55501. Those were the military numbers, the commercial, I beleive, were 75500 and 75501.
Does anyone know if multiplexing Nixies will significantly reduce their
lifespan? Or does it in fact help versus "permanently on as needed"?
I'm not sure if it's rapid hot-cold switching that'll kill them or if it's
simply down to "on time"... (or even neither :-)
I'm reviving the Nixie-based Sudoku idea mentioned on here in the past as I
think I've found a good source of tubes in the Ukraine. Latching every digit
isn't an option (due to sheer number of ICs required), but likely failure
causes dictates how many tubes will participate in each multiplex...
cheers
Jules
> Does anyone know if multiplexing Nixies will significantly reduce their
> lifespan? Or does it in fact help versus "permanently on as needed"?
Looking at the datasheet for the non multiplexed GN4 nixie the different
cathode currents are given as ..
Cathode current 2mA
Maximum continuous current 3mA
Maximum pulse current 4mA
.. So from that I'd guess multiplexed nixies are a special breed.
Lee.
>
>Subject: Re: Copying DEC VAX set up disks rx50, help
> From: "Chuck Guzis" <cclist at sydex.com>
> Date: Mon, 05 Mar 2007 16:19:46 -0800
> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>At sometime today, Allison wrote:
>
>> It's not 300 data rate it's 250!
Thats out of context. When I say 250 data rate I refer to the nominal
speed drive it was intended for (300 RPM) not the 1.2mb aberation.
I helps to know what the source media is for and in the case of DEC
the formats are limited in number used are easy to get data about
and recognize. Of course the file organization on that media can be
far more varied in the DEC cases A partial list includes (on floppy):
POS, RSX-11, DOS, RT-11, RSTS, Files-11, ultirx-11
VMS, VMS saveset, ultrix/VAX,
formats used for MIPS based systems,
OS8/78/278
DECmate WPS systems.
VT180 Robin (CP/M on RX180)
I likely missed something. However, the media if floppy based is
only RX01/2 (8"), RX50, RX33, and late in the game RX25(3.5" 720k) and
(RX26 3.5" 1.44m).
I understand reading a DD 5.25" disk on a 360rpm fixed speed 1.2mb drive
will give 300 as data rate. I tend to treat and sequester all 1.2/1.6mb
5.25 disks away from all other rates as they are usually PC application
with an exception outside the PC application space (RX33 for example).
So the PC I have for reading disks is a older 486/66 with three drives
on two controllers. The drives are standard 3.5" that does both 720 and
1.44m, 360k (48tpi FD55BV), FD55F for 96tpi DD (formats like RX50). I
do not bother with PC 1.2MB format and the only place it appears here
is DEC RX33 disks that my PDP11[Qbus 11/73 with an RQDX3/RX33) handles
as native. Even that PDP-11 is an unusual nonDEC configuration as it has
RX02, RL02, RX50/33 and RD52(2 of them) in a rack mount format.
I have Imagedisk, Fcopy, and teledisk and it runs dos/win95 for networking.
this makes for a predictable PC based system that is well behaved reading
formats like RX50. It was easier to put an old 486/66 minioard in a small
tower with all the disks as I had it and the ISA floppy controllers, NIC and
all needed. It has a small 420mb disk for local storage and programs
as that all that is needed sice with networking I can mount the selected
drive and copy from there usless it's an nonPC format.
For those times when it's not PC based there is a NS* crate with NS*
controller for hardsector two of my intelligent controllers for
8"/5.25"/3.5" formats that occur in the CP/M and NS*dos worlds.
>Well, let's see what the numbers say.
>
>360 RPM is 6 revolutions per second or 0.167 second/revolution
>300 RPM is 5 revolutions/sec or 0.200 seconds/rev.
>
>Thus, the raw capacity of a 300 RPM drive at 250Kbps is 50,000 bits
>or 6250 bytes. The raw capacity of a 360 RPM drive at 250kpbs is
>41667 bits or 5208 bytes.
>
>On the RX50, since there are 10 sectors of 5120 bytes, we have
>
>6250-5120 = 1130 bytes for gaps and ID marks, CRCs, etc. on a 300 RPM
>drive. On a 360 RPM drive, one has 5208-5120 = 88 bytes for all that
>overhead. Not considering gaps yet:
>
>There are 10 bytes for a IDAM: A1 A1 A1 FE cc hh rr nn cr cr, where
>cc is the cylinder number, hh is the head number, rr is the sector
>number, nn is the sector length code and cr cr is the CRC for the
>IDAM. To that, add the data preamble of 4 bytes A1 A1 A1 FB and a 2
>byte CRC and you have (without gaps) 15 bytes per sector or 150 bytes
>for a 10-sector track--and we're out of space already at 360 RPM
>before we can add the barest of gaps (e.g. 12 bytes of 00 preamble
>for the IDAM, 12 bytes of 00 preamble before the DAM...
>
>You just can't do it at 250Kpbs and 360 RPM. Heck, 10x512 is a
>fairly tight fit at 300 RPM.
>
>Cheers,
>Chuck
I agree! The trouble maker is the interrecord gaps when added to the data
fields and other "position" fields like IDAM space becomes very tight.
DEC solved this partially by truncating the end of track gap and the
Index gaps making it harder to read with a FDC that was designed
to expect them.
Allison
>
>Subject: Re: Copying DEC VAX set up disks rx50, help
> From: "Chuck Guzis" <cclist at sydex.com>
> Date: Mon, 05 Mar 2007 14:22:39 -0800
> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>On 4 Mar 2007 at 18:00, Allison wrote:
>
>> Wrong. The RX50 format and RX33 formats are very differnt...
>
>Ah. So an easy accommodation is to declare a 360RPM 1.2MB drive as a
>1.44MB 3.5". That keeps the 250Kbps data rate for low density while
>the drive keeps spinning happily at 360 RPM. There's still the issue
>of the missing IAM gap, but some National chips (8473 IIRC) seem to
>be a bit more tolerant.
>
>Cheers,
>Chuck
DEC did do 3.5" formats those wer RX25(720k) and RX26(1.44m) and they did
appear on later uVAX3100s.
Allison
While repairing our VT11 that hangs the Unibus as soon as you point the
light pen to the high frequency fluorescent room illumination (which makes
playing lunar lander a pain) I've discovered that the schematics of the
M7014 board (bus control & bootstrap) as found in the GT40 engineering
drawings (from bitsavers) do not correspond to our board (a M7014-YA).
The document number for the M7014 board is D-CS-M7014-0-1.
Does anyone have the document numbered D-CS-M7014-YA-1 in electronic form
(or even the complete VT11 engineering drawings)?
Christian
