Tony wrote (in the discussion of ZX80s and PERQs):
> The other point is that many features of today's computers can be traced
> back to the PERQ/D-machines, etc. There aren't that many features that
> can be traced back to the ZX80.
Are you sure the PERQ was very influential. It was more of a commercial machine
than the Xeroxes, possibly, but I think the Xerox ideas would have had the same
influence on modern computing without the PERQ.
>> Sorry, Tony, I must agree with Glen here. Sinclair did not go to the trouble
>> that Apple and Microsoft have since expended to separate the user from the
>> nitty-gritty of how the machine works. The Sinclair is a far better machine
to
>
> Are you suggesting that PERQ systems did? Heck, you get a microcoding
> manual with the machine. The microcode assembler and placer are on the
> standard system distribution.
Not in the least.
> When you get into it, you'll learn a lot more from a PERQ than from a
> Sinclair....
Possibly. But you cannot assign more significance to the PERQ because it was a
better machine to learn on. Both the PERQ and the ZX80 were far better to learn
on than a PC clone. The ZX80 could teach you about microprocessor systems
(after a fashion), the PERQ about minicomputers and microcoding. The designers'
intentions were probably that the ZX80 was _meant_ to be educational, while the
PERQ was meant for experienced computer buffs to design specialist application
specific software and peripherals. The ZX80 is certainly more significant in
the amount of learning (people educated * some measure of knowledge gained, or
rather sum over people educated of amount of knowledge gained) that was done on
it.
So in some sense the ZX80 is more significant. But In other ways, as Tony
pointed out, it is less significant. Swings and Roundabouts. But I agree that
the ZX80 does not deserve the inflated colletors' prices...
Philip.
Long weekend syndrome: Some of these threads are several days old. Please bear
with me in this and the next few replies.
Glen wrote (in a discussion of the relative significance of ZX80s and PERQs):
> What was the first sub-100-pound computer (MK14??)
That is indeed the one I had in mind. I think there may have been one or two
other kit machines in that price bracket (Nascom?)
Philip.
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Hi Tony,
>The disk controller board can handle 2 floppy drives, and all
>the machines I've seen in the UK had that configuration.
I wonder if this is some sort of regional thing here in the UK....I've seen
plenty of HD Sirii around the Midlands, roughly twice as many as twin floppy
machines in fact?
TTFN - Pete.
--
Hardware & Software Engineer. Sound Engineer.
Collector of Arcade Machines, Games Consoles & Obsolete Computers (esp DEC)
peter.pachla(a)virgin.net |
peter.pachla(a)vectrex.freeserve.co.uk |
peter.pachla(a)wintermute.free-online.co.uk | www.wintermute.free-online.co.uk
--
I have what claims to be an IBM master alignment tape. I haven't looked at
it in detail in over 20 years, but I just saw it yesterday. Is this
somehing you (or all of you) could use?
Dick
-----Original Message-----
From: Jay West <jlwest(a)tseinc.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Tuesday, July 06, 1999 9:28 AM
Subject: Re: Advice wanted on Kennedy 9600 and PDP11/23
>Now that my TC02 is re-installed, it won't work at all. The select light
>never comes on. ARGH!!! I'll fiddle with it later today since I'm off work.
>
>If I can't get it working, would anyone be willing to convert some 800bpi
>tapes to 1600bpi for me? The tapes are the initial load tapes for
>HP2000Access (Timeshare BASIC). My 7970E doesn't speak 800bpi, so I need to
>convert them. Of course, the tapes are priceless to me <grin> so I'm loath
>to send them out, but they are useless at 800bpi.
>
>On the other hand, I was wondering about what is involved in making my
7900E
>read 800bpi? ISTR that different heads are needed - which it too much
>modifications to me. GRrrrr....
>
>>It takes a master alignment tape, a scope, and a resistor network that
sums
>>the outputs from the tape channels. The master alignment tape has
>transitions
>>that are supposedly well-aligned between all channels, and you tweak the
>>head until you get a nice pattern on the scope. I can fax you a few pages
>>from drive maintenance manuals on the procedure if you're really
>interested.
>
>
>Well, I have the scope (20mhz ok?), but no alignment tape or resistor
>network.
>
>Thanks in advance for all the help!
>
>Jay West
>
Hi,
>Please snip off excess text while replying....
I'd like echo this sentiment.
Of late I've been receiving quite a few messages which quote the entire message
and just add a line or two to the end....many of there are quite large messages
(over 6K) and for some reason I end up not being able to download them from my
mailbox (I cannot even telnet in and view them on-line).
All I can do is delete them from my mailbox, it's very frustrating as I'm
therefore losing parts of threads - usually ones which I'm trying to follow....
TTFN - Pete.
--
Hardware & Software Engineer. Sound Engineer.
Collector of Arcade Machines, Games Consoles & Obsolete Computers (esp DEC)
peter.pachla(a)virgin.net |
peter.pachla(a)vectrex.freeserve.co.uk |
peter.pachla(a)wintermute.free-online.co.uk | www.wintermute.free-online.co.uk
--
Now that my TC02 is re-installed, it won't work at all. The select light
never comes on. ARGH!!! I'll fiddle with it later today since I'm off work.
If I can't get it working, would anyone be willing to convert some 800bpi
tapes to 1600bpi for me? The tapes are the initial load tapes for
HP2000Access (Timeshare BASIC). My 7970E doesn't speak 800bpi, so I need to
convert them. Of course, the tapes are priceless to me <grin> so I'm loath
to send them out, but they are useless at 800bpi.
On the other hand, I was wondering about what is involved in making my 7900E
read 800bpi? ISTR that different heads are needed - which it too much
modifications to me. GRrrrr....
>It takes a master alignment tape, a scope, and a resistor network that sums
>the outputs from the tape channels. The master alignment tape has
transitions
>that are supposedly well-aligned between all channels, and you tweak the
>head until you get a nice pattern on the scope. I can fax you a few pages
>from drive maintenance manuals on the procedure if you're really
interested.
Well, I have the scope (20mhz ok?), but no alignment tape or resistor
network.
Thanks in advance for all the help!
Jay West
>>What is the third party card?
>It's an Emulex. The card has silkscreened Assy TU0210401 REV C. One one of
>the chips, it says Top Assy TC0210201-FSH, Sub Assy C6716 C.
OK, I use many TC02's here, and have never had a problem at 800 BPI.
(The only density problems I've had have been on Dilogs, having to do with
expecting PE bursts at the beginning of the tape.)
>>Well, the tape does need to be re-inited at the new density. Are you
>>doing the INIT before the BACKUP, or doing a BACKUP/INIT? Does the INIT
>>operation work OK? Can you do a DIR MS: after the INIT at 800 BPI?
>In my version of RT11 (5.04), /init isn't a valid option on the backup
>command.
Historically, the BUP.SAV options have been out of sync with the CCL BACKUP
(command line) options for many versions of RT-11. This was always
a damn shame, as it discouraged folks from using BACKUP. Things get fixed
in 5.5 and later.
> But, when I do a backup/dev du1: ms0: it does ask if I want to
>initialize, that seems to complete, then the backup goes on and finally an
>output error. Once I get the tape controller reinstalled, I'll tell you for
>sure.
What happens if you just INIT MS0: and COPY a couple of files to it?
Can you read them back off at 800 BPI?
BACKUP uses 4096-byte blocks, while the COPY (PIP.SAV) operations use
512-byte blocks. It's conceivable that you'll only have troubles with
the long blocks.
>>I'll also point out that NRZI requires a lot tighter physical tolerances
>>on the alignment of the tape head (the reason why many drives don't support
>>800 BPI NRZI at all) than 1600 and 6250 BPI (which allow substantial skew
>>between the tape channels as part ofthe spec.) If at some point the head
>>in your transport had been replaced or knocked around without properly
>>being re-aligned you might see something like what you're seeing.
>Really! I didn't know that.
Yep. NRZI is a pretty low-tech interface, and it relies entirely on
good alignment of the heads for timing. PE and GCR allow skews of up
to several bits that are disentangled by the electronics in the formatter.
> When I got the tape drive, it had been in
>storage and was immaculately clean. Other than usual wear on the door, it
>looked in fantastic condition. What's involved in aligning the heads? I take
>it I would need an alignment tape? 1600bpi seems to work great though, both
>reading and writing.
It takes a master alignment tape, a scope, and a resistor network that sums
the outputs from the tape channels. The master alignment tape has transitions
that are supposedly well-aligned between all channels, and you tweak the
head until you get a nice pattern on the scope. I can fax you a few pages
>from drive maintenance manuals on the procedure if you're really interested.
Many drives do deskewing of NRZI in electronics (usually with shift registers
running at several time the data rate) in addition to having the head being
aligned correctly overall.
--
Tim Shoppa Email: shoppa(a)trailing-edge.com
Trailing Edge Technology WWW: http://www.trailing-edge.com/
7328 Bradley Blvd Voice: 301-767-5917
Bethesda, MD, USA 20817 Fax: 301-767-5927
Tim wrote...
>What is the third party card?
It's an Emulex. The card has silkscreened Assy TU0210401 REV C. One one of
the chips, it says Top Assy TC0210201-FSH, Sub Assy C6716 C. Two 50 pin
ribbon cables look pretty Pertec-ish to me. There's a 4 switch dip and LED
between the ribbon cables. There's also a 20 pin header (2 rows of 10) on
each side of the ribbon cable connectors. In the center of the board are two
10 position dip switches. There's 3 sets of wire wrap jumper pins as
follows: at the top A,B,C,D in the middle E,F,G, and at the bottom H,J,K,L.
On my board, the 4 switch dip SW1 has all switched towards the PCA (closed).
On the center two 10 position dips, SW2 is all down or off except #8; SW3
all are down or off except #1,3,7,8. On wirewraps, A-B, C-D,E-F. There
appears to be a few ECO wires added to the board too.
>Well, the tape does need to be re-inited at the new density. Are you
>doing the INIT before the BACKUP, or doing a BACKUP/INIT? Does the INIT
>operation work OK? Can you do a DIR MS: after the INIT at 800 BPI?
In my version of RT11 (5.04), /init isn't a valid option on the backup
command. But, when I do a backup/dev du1: ms0: it does ask if I want to
initialize, that seems to complete, then the backup goes on and finally an
output error. Once I get the tape controller reinstalled, I'll tell you for
sure.
>I'm not awfully familiar with the Kennedy 9600, but if it's like the 9614
>it supports 800, 1600, 3200, and 6250 BPI. Yours is the Pertec-formatted
>(two 50-pin cables) interface?
Yup, pertec. It would appear to support 800 and 1600, because the density
switch toggles between PE and NRZI one at a time (plus a remote setting for
each).
>I'll also point out that NRZI requires a lot tighter physical tolerances
>on the alignment of the tape head (the reason why many drives don't support
>800 BPI NRZI at all) than 1600 and 6250 BPI (which allow substantial skew
>between the tape channels as part ofthe spec.) If at some point the head
>in your transport had been replaced or knocked around without properly
>being re-aligned you might see something like what you're seeing.
Really! I didn't know that. When I got the tape drive, it had been in
storage and was immaculately clean. Other than usual wear on the door, it
looked in fantastic condition. What's involved in aligning the heads? I take
it I would need an alignment tape? 1600bpi seems to work great though, both
reading and writing.
Any help is most appreciated!
Jay West
<Hmmm, the PS/2 Model 50 is a Micro Channel based system IIRC, which wasn't
<even supported under Linux until recently. Then there is the question of
<what kind of HD does it have? If it's ESDI that might be a problem, thoug
<at 20Mb, I'd guess a MFM drive, which shouldn't be a problem. I think the
<real question is, does Minix 2.0 support the PS/2.
Minix supports 8086 through Pentium. the PS2/50 is 286. The 20mb is MFM
maybe edsi it's oddball so it's hard to tell. Anyway MINIX questions
should really be addressed to the Minix list and Andy Tannenbaum does
reply there so what better source!
Allison
<machines. Pine users shouldn't complain too much, since you can set it up
<to launch a web browser for inline URL's in mail messages. I have mine
<launch lynx by default, but the nice thing about SSH is that you can
Yes it can but via a really crummy ISP I use for the telnet link to World
it's out of the question, tooooooooo SLOWWW. I do that to keep personal
traffic of the work ISP and net.
A one line description really is the answer.
Allison
