<OK, so the next question: is getting an education (enough to give one a
<chance) that tough overseas? It is not hard at all here in the states -
My understanding is not any harder than here. breaking into the hardware
field is a bit harder than software and many here (USA) in the internet
services (web, java and all that rot) are likely self educated people with
non-technical degrees.
The tag along issue was hobby vs vocation.
<summer at hamfests, selling electronic castoffs - even junk. Fill a box
<with caps, switches, tubes, connectors, knobs, etc., and the
<homebrewers will come. Yes, they tend to be a cheap lot too, but it adds
<up. Anyway, by October, an Altair could be possible - or even a pile of
<other machines.
This is very true. If you want to find stuff you have to be "out there"
or you'll miss a great amount.
For example at a MIT flea I got a very since BA11 11/23 system with docs,
floppies and RX02 for $0.00 as the owner didn't want to haul it back.
<Being a hamfest seller is a GREAT way to get leads, as well.
No kidding.
<Of course, I have never been to a radio rally, so things might be
<different for sellers.
Maybe, I'd bet not. ;)
Allison
Thanks to all who have responded so far.. I have tracked the
trouble to code level 5.. I have the parity keyboard with split
shifts and '5' is stuck marking all the time. I put myself to sleep
last night reading the maintenance manual, after lunch I'm gonna
dive into it.
WooHoo!
Cheerz
John
>The RD53 I have here has the W1 and W2 in place, the next three pins are
>DS (drive select) ID settings, DS1, DS2, or DS3. I seem to recall that
>the drive has to be set as DS2 to be the primary drive on an RQDX3
>controller.
No. The floppies are DS1 and DS2. The hard drive should be DS3. If
your system has a second drive, however, you may need to set this to
be DS4.
Depends on what else you have and how it is all wired.
What system box? (BA23? BA123?)
Direct connect to controller? (Leprechaun box?)
Connection through signal card? (RQDXE? BA23 backplane?)
More info is needed.
Megan Gentry
Former RT-11 Developer
+--------------------------------+-------------------------------------+
| Megan Gentry, EMT/B, PP-ASEL | Internet (work): gentry!zk3.dec.com |
| Unix Support Engineering Group | (home): mbg!world.std.com |
| Compaq Computer Corporation | addresses need '@' in place of '!' |
| 110 Spitbrook Rd. ZK03-2/T43 | URL: http://world.std.com/~mbg/ |
| Nashua, NH 03062 | "pdp-11 programmer - some assembler |
| (603) 884 1055 | required." - mbg |
+--------------------------------+-------------------------------------+
Hi Brian:
You may be a victim of the infamous "RD53 spindown problem". Does the
drive spin up and then stop and/or recycle, or fail to reach full speed?
If so you likely have a spindle break solenoid problem, which can be fixed
with a small Phillips screwdriver.
Please chack this and get back to me, I'll give more detailed instructions
if indeed this is what's happening.
> : | : : | |
>
> D S W W
> 4 3 2 1 2 1
The RD53 I have here has the W1 and W2 in place, the next three pins are
DS (drive select) ID settings, DS1, DS2, or DS3. I seem to recall that the
drive has to be set as DS2 to be the primary drive on an RQDX3 controller.
The one in front of me is set to DS1 however.
I have three other RD53s in storage, I can check on Monday if necessary,
but jumpering may not be the problem. You might contact Megan or Allison
on the list.
I forget what W1 and W2 are for, but my drive has them in place.
Hope this help,
Kevin
--
Kevin McQuiggin VE7ZD
mcquiggi(a)sfu.ca
<Thanks for the info. As far as I've been able to find out, which is lillt
<more than speculation, I'm afraid, these "MITS Hard Disk Controller" boxes
<were just prepared for trade shows and demos and were never mass-produced.
<Since I can convert them into something useful without damaging them in an
<way, I'll go ahead and do that. It would appear there were fewer than hal
<a dozen of these made, and they were never mmass-marketed.
<
<Dick
What about after the Pertec guys bought them, I thought the marketed a
MITS hard disk? though I think it was a 10mb 14" removable.
Allison
<Boy does that sound like spec. inflation! 24 p-p is just 12 Volt peak in
<either polarity with a bridge circuit. That gives 12/8 peak amps and 18
<peak watts (like with a +/-12 volt square wave). The RMS voltage and
no that would be 24/4 (two speakers presuming they are parallel) or 6A.
Assumes a 100% lossless bridge amp. at 24VPP and 6A you have 144W if it's
a symetirc squarewave, less if sine(RMS).
Now reality sets in, using the latest devices (VMOS/hexmos) there will be
a few tenths of a volt loss arcoss the device. So let say the loss is 1V
in that bridge amp of ours. Not allowing for resistance of wire and also
assuming the PSU can easily supply in excess of the required current at
12V.
23Vpp/4 = 5.75A that times 23 is only 132.25... reality sets in some.
also the difference 11.75W is heat!!! and thats the squarewave, it gets
really bad for sincewaves (more like 25W as heat!). Can you imagine
trying to get rid of say 40-50W (stereo case) of heat from one of those
tiny boxes?
Other assumptions, an 8ohm speaker is 8ohms. A non truth as it varies
widely with frequency assuming a good encolsure. So at one frequency it may
look like 6ohms and at another 15! Then we have copper losses from wiring
and PC traces (resistance) and what if the 12V is really 11.95V?
<amplifier. Don't tell me these "240 Watt" speakers are powered by 4 "AA"
<batteries ;)... or use one of the many automobile ic amps that give about
<4.5 watts with a 12 Volt supply and a 4 Ohm speaker.
The other reality is it takes very few watts at a sustained level to cronk
ones ears forever.
4AA cells can provide a remarkably large amount of power for and equally
remarkably short period of time. (nominally 3WH) ;)
A real 240W amplifier will cook a hotdog with two nails stuck in the
ends in about 2 minutes at sustained full power! Real power = heating
power.
Allison
S100 was one of the first to see people using different cpus as they could
still use their old boards (sometime with mods) or they could "bend"
the cpu to fit the bus adaquately.
<You may indeed be onto something here, Allison, but the ISA is no less
<general in its inherent qualities than the S-100, and I'd submit that a
<major case for the S-100's popularity for non-8080 applications was the
<ready commmmercial availability of numerous desirable functions at
<reasonable prices. That's how the ISA occurred to me.
Indeed, the key was commonly available generic functions. ISA8/16 fits
the bill fairly well. Infact myself and another are working on a ISA16
motherboard with a z280 insted of intel. Why, keyboard, serial, video,
floppy and hard disk interfaces are all done and cheap to free. We do not
need a raft of interrupts, so thats not a big problem. It's not a perfect
match but general enough if we bend a rule or two it will be fine. After
all we want to run z280s at full bore speed for software development and
the specifics of the platform are relitively unimportant other than we'd
like the two of them to be the same.
In 1989 S100 would have been a choice for the same reasons.
<Aside from that, a general purpose not processor-biased architecture would
<provide a few control signals, e.g. IORD, IOWR, MEMRD, MEMWR, maybe a coupl
<of clocks, probably one fairly fast one suitable as a dot clock for a vide
<circuit, and one slower, suitable for bus transaction timing, a few
<interrupt and DMA support signals, and a couple of dozen address lines.
<Parity and maybe a "tilt" line would be handy, as well as a wait signal.
<Most busses have these signals in one form or another.
Sounds like ISA. ;) If memory is kept off the bus ISA is just fine for
most 8/16 bit cpus I can think of. The only provision would be the cpus
that may DMA impossible or very painful but even then DMA is not a required
capability for some smaller designs.
<The key element for generalized development, though, is whether or not you
<can afford to buy the functions you don't want to build right away. Don't
<you agree?
Bingo! or for many reasons don't care to build. A 16450/16550 serial is
uninteresting but, serial is one of those must haves in a system like
mabe a modem. Others make little sense to fabricate when even new
they are under $50!
Allison
The boxes I bought were sold to us by an agent for Pertec, which was
liquidating the MITS stuff. The FDD and HDD used with Altairs were
Pertec's, since they worked closely with the MITS boys. Unfortunately their
FDD and HDD were a bit out of date. They probably saw the 8-bit market as a
place to dispose of the stuff no longer suitable for mini's.
Dick
-----Original Message-----
From: Allison J Parent <allisonp(a)world.std.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Saturday, July 03, 1999 12:37 PM
Subject: Re: Ed Roberts
>
><Thanks for the info. As far as I've been able to find out, which is lillt
><more than speculation, I'm afraid, these "MITS Hard Disk Controller" boxes
><were just prepared for trade shows and demos and were never mass-produced.
><Since I can convert them into something useful without damaging them in an
><way, I'll go ahead and do that. It would appear there were fewer than hal
><a dozen of these made, and they were never mmass-marketed.
><
><Dick
>
>What about after the Pertec guys bought them, I thought the marketed a
>MITS hard disk? though I think it was a 10mb 14" removable.
>
>Allison
>
>
