Hi all - I'm new to the list, been lurking for a while. By way of
introduction, back in the 80s I was a bonified software developer (wrote
a mag tape locking device for an early version of UNIX back when there
wasn't such a thing, did work in telecom test equipment and speech
recognition for years) but these days I'm in the old/rare book business,
technical books and all. I like old hardware, though don't have the
storage space for much. When I was in high school I took apart a Friden
computyper in my parents basement just to see what was in it. Still
have the "core memory" board around here somewhere. I've tried to
salvage manuals for old computers, component manufacturer technical
books, and an IMSAI or two over the years. Still have 20 boxes of old
components (everything from transistors, caps, resistors, etc to tubes)
in the garage I've accumulated over the years when I'm buying old books
>from hobbyists - buried deep enough I don't even remember what's in them.
Anyway, a friend asked me to try and sell a DEC Robin for him (he tells
me it's a DEC VT180 with a separate drive unit that he tells me was only
available to DEC employees), and my question is this:
Is it safe to try and plug this machine in and try to power it up? I've
seen various discussions about old capacitors dying, etc but I'm not
sure if this machine is old enough to worry about. My plan was to try
and power it up (my consignor also gave me some software with it, not
sure if it's related or not yet), and see if it still ran ok, take some
photos for the group (if anyone wants to see it) and my own records, and
then try to sell it. It appears to be in good shape, in the original
boxes, "monitor" in one box w/keyboard (looks to be a VT180), and a disc
drive unit in the other. My consignor said it ran the last time he had
it out many years ago. I've always enjoyed and preferred photographs of
old machines with their startup screen displayed rather than a dark
screen. Seems like they have more life with a live screen.
Any pointers appreciated (on or off list) - what to do or check in what
order would be great. Its been a long time since I blew up directional
capacitors in lab...so long I don't even remember what they're called.
Thanks in advance!<grin>
--
Sincerely,
John Kuenzig, Bookseller
Kuenzig Books
PO Box 452, Topsfield, MA 01983
978-887-4053 9am-7pm Eastern Standard Time
866-512-3053 tollfree 9am-7pm EST
orders at kuenzigbooks.com (orders or inquiries)
Important Books in Science, Technology and Speculative Fiction
Secure ordering at http://www.kuenzigbooks.com
Save time, money and earn other exclusive benefits.
Members of:
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Buying 18th-21st century books, manuscripts, ephemera,
scientific instruments, artifacts, and related material
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________________________________
On Sunday 08 June 2008, Andrew Lynch wrote:
> During the design, I wrestled with Flash ROM versus EPROM for quite a
> bit.
>
> I went with EPROM since they are unchangeable in circuit and have
> larger capacity for the same 32 pin socket.
>
> My assumption was with cheap and plentiful EPROM programmers (search
> for Willem on eBay ~$20) that practically everyone interested would
> have one.
>
> Flash ROM has its advantages but requires more advanced software for
> in circuit reprogramming. The software would have to be written too.
Flash should actually be easier than an EPROM to program, especially
in-circuit, as it's designed to do that.
If you're worried about accidental erasure, just throw a switch or
jumper on the board to disable the /WE input to the flash.
Pat
--
Purdue University Research Computing --- http://www.rcac.purdue.edu/
The Computer Refuge --- http://computer-refuge.org
________________________________
-----REPLY-----
Hi Pat,
Well, in theory you may be right but this SBC has already been designed and
manufactured.
The PCB exists and is shipping now so it is a bit late for the initial
design considerations.
I understand the appeal of Flash ROM but the parts are more expensive and
many can be corrupted in circuit with errant software.
Even with code protection modes, there is no guarantee of non-corruption on
Flash ROMs.
At some point you'll have to lower the protection if you ever want to write
to that part of the chip.
In circuit reprogramming ability opens the door for those sorts of bugs to
creep in to the code.
EPROMs cannot be corrupted in circuit, short of a broken component, AFAIK.
Some Flash ROM chips do support code protection but not all.
Really, any part you select for this job has its costs and benefits. It all
gets down to trade offs.
One of my primary goals of the SBC is to keep the overall cost to a minimum
while providing something useful.
Generally speaking, EPROM is cheaper than Flash ROM and also has larger
capacity. The price is requiring external programming and erasing.
Incorporating EPROM is also requires less complex circuit and the software
is easier to write and debug.
There is no chance of "bricking" the SBC due to a bug in the CBIOS code
either.
At least in this case, I am also more familiar with the technology and I was
able to reuse my prototype design almost as is.
Not having to write special software was a big plus too. In short, EPROM
seemed like a hands down winner.
What caught me by surprise was the larger than expected demand for the
pre-programmed EPROMs.
Even that isn't really much of a problem since if I can't find a source for
low cost used parts, I can just buy a tube or so of new ones from Jameco.
Brand new, they only cost $6.25 each when you buy 10 or more.
I can just raise the price of the EPROM but I would rather keep it as low as
possible.
Thanks for the help and comments. Please let me know if anyone gets any
other ideas.
Have a nice day!
Andrew Lynch
PS, I did some investigating and experimenting with the 29F020 style chips.
It turns out making a shim socket for getting them to work is trivial. I
have several compatible chips on hand. It still doesn't add in circuit
reprogramming but even that would be fairly easy with some cuts and jumpers
and appropriate software.
I'm looking to buy 1 or 2 DS-1216e chips (they're clock chips) but am
having trouble finding a reseller/distributor that will sell them in
lots of less than 300. Does anyone know of a reseller for ICs that has
somewhat reasonable one-off prices?
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
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________________________________
Glen wrote:
> Digi-Key lists the M27C801-100F1 @ $7.12 each for q >= 10.
> IC EPROM 8MBIT UV 100NS 32-FDIP
>
> That's not too far away from $5 ...
Though it's an OTP, so as soon as you need to reprogram it once, you've
lost the cost savings.
-----REPLY-----
Regarding the OTPs, I agree and am looking for the UV eraseable EPROMs.
Possibly, 27C4001 chips may work as an alternative and they are being sold
by Mr. EPROMMAN. I'll get one soon and test it.
I would really like to avoid OTPs as the primary method to update the
software on the SBC is to download and/or create a new ROM image.
OTPs have their uses and could be a "fall back to known good" chip but the
lack of reprogrammability makes them wasteful in my mind.
During the design, I wrestled with Flash ROM versus EPROM for quite a bit.
I went with EPROM since they are unchangeable in circuit and have larger
capacity for the same 32 pin socket.
My assumption was with cheap and plentiful EPROM programmers (search for
Willem on eBay ~$20) that practically everyone interested would have one.
Flash ROM has its advantages but requires more advanced software for in
circuit reprogramming. The software would have to be written too.
Some Flash ROM chips have "code protect" modes as well which make them more
reliable.
I am considering some possible modifications to the design using shim
sockets to convert to Flash ROM as they are very cheap and readily
available.
The best design would be flexible and accept either chip but there are
differences in pin outs that prevent "drop in" replacements from working.
I have already tested a variety of Flash ROM devices with no luck so far.
The best solution though, IMO, would be a low cost source of used
27C080/27C801 chips.
There has to be someone out there with lots of surplus used 1Mx8 chips
laying around. They were common as dirt just a few years ago.
Thanks and have a nice day!
Andrew Lynch
I just got this in email from a friend, and thought the list might be
interested.
http://waxy.org/2008/06/the_machine_that_changed_the_world/
The Machine That Changed the World: Great Brains
Posted Jun 3, 2008 (Updated Jun 4, 2008)
The Machine That Changed the World is the longest, most comprehensive
documentary about the history of computing ever produced,
but since its release in 1992, it's become virtually extinct. Out of print and
never released online, the only remaining copies are VHS
tapes floating around school libraries or in the homes of fans who dubbed the
original shows when they aired.
It's a whirlwind tour of computing before the Web, with brilliant archival
footage and interviews with key players ? several of whom
passed away since the filming. Jointly produced by WGBH Boston and the BBC, it
originally aired in the UK as The Dream Machine
before its U.S. premiere in January 1992. Its broadcast was accompanied by a
book co-written by the documentary's producer Jon
Palfreman.
With the help of Simon Willison, Jesse Legg, and (unofficially) the Portland
State University library, we've tracked down and digitized
all five parts. This week, I'm uploading them, annotating them with Viddler, and
posting them here as streaming Flash video as they're
finished. Also, the complete set will be available as high-quality MP4 downloads
via BitTorrent by Friday.
Here's the first of the five-part series, The Machine That Changed the World.
Enjoy!
Note: Like all the other materials I post here, these videos are completely
out-of-print and unavailable commercially, digitized from old
VHS recordings. If they ever come back into print, or the copyright holders
contact me, I'll take them down immediately.
Looking for 1Mx8 EPROMs (27C080 or 27C801)
Al Kossow aek at bitsavers.org
<mailto:cctalk%40classiccmp.org?Subject=Looking%20for%201Mx8%20EPROMs%20%282
7C080%20or%2027C801%29&In-Reply-To=>
Sat Jun 7 16:15:04 CDT 2008
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________________________________
> I'd like to keep the costs as low as possible and am trying to keep the
> EPROM at or below $5 each.
How much of the megabyte of space have you ACTUALLY used?
A meg of EPROM seems insane to me for a low-cost SBC.
________________________________
* Previous message: Looking for 1Mx8 EPROMs (27C080 or 27C801)
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-----REPLY-----
Hi Al,
Insane is such a harsh word... :-) I consider it a slight modern
adaptation to a Z80 SBC designed in the classic vintage style.
Of the 1MB EPROM, the current SBC uses a little over 128K. It includes the
boot loader, RAM monitor, CP/M boot image, the standard transient CP/M
commands, the VDE full screen editor, BBC basic, and a smattering of small
utilities like the RTC, XMODEM5, and start-the-RAM-monitor-from-CP/M. The
rest of the EPROM is reserved for user expansion in the various CP/M USER
spaces.
The SBC really only needs probably 4K or so to boot the RAM monitor but the
rest of the ROM is used as CP/M block devices (32K A: and 992K F: drives).
There is also a 448K RAM block device for CP/M drive B: for temporary files
in addition to the full 64K main memory for the OS and RAM monitor.
Memory block devices allow the SBC to have a usable and reliable OS for
relatively easy user expansion without the hassle and reliability issues of
real disk devices. Real disk drives are supported (IDE and floppy) on a
Disk IO board I built on the prototype. I plan to make a PCB for later on.
Disks are good things but I made them an option rather than a requirement to
keep it simple.
Believe me, a 1MB EPROM block device is *MUCH* less expensive than adding
even the least expensive floppy drive controller and even IDE. The ROM
control circuitry is there regardless of size and the cost difference
between a 27C64 and a 27C801 is minimal in the overall cost. The benefits
of reliable storage tremendously outweighs the minor extra cost, IMO.
Thanks and have a nice day!
Andrew Lynch
Andrew,
eBay is usually the place to find used eproms
here's one #330229142491
lot of 11pcs @ $47.95 'Buy it now'
there's 4 lots left
That's about $5 each *after* shipping
=Dan
[ RFK ]
[ Pittsburgh --- http://www2.applegate.org/~ragooman/ ]
Andrew Lynch wrote:
> Hi,
>
> I am searching for some used 1Mx8 32 pin DIP UV EPROMs like 27C080 or
> 27C801.
>
> If anyone can help out or knows a low cost supplier of 1Mx8 EPROMs, I
would
> much appreciate it.
>
> THANK YOU IN ADVANCE FOR ANY HELP!
>
> Andrew Lynch
>
>
>
>
-----REPLY-----
Hi Dan, Thanks!
Yes, I found those on eBay and bought some.
They should be enough so I can finish this round of PCBs without running out
of EPROMs.
I checked with the helpful people at Mr. EPROMMAN and I think I may be able
to substitute a 27C4001 for the 27C801.
They are only half the size but they are available used, inexpensive, and in
quantity.
Thanks and have a nice day!
Andrew Lynch
Hi,
I am searching for some used 1Mx8 32 pin DIP UV EPROMs like 27C080 or
27C801.
If anyone can help out or knows a low cost supplier of 1Mx8 EPROMs, I would
much appreciate it.
THANK YOU IN ADVANCE FOR ANY HELP!
Andrew Lynch
>
>Subject: Re: Looking for 1Mx8 EPROMs (27C080 or 27C801)
> From: Al Kossow <aek at bitsavers.org>
> Date: Sat, 07 Jun 2008 14:15:04 -0700
> To: classiccmp at classiccmp.org
>
> > I'd like to keep the costs as low as possible and am trying to keep the
> > EPROM at or below $5 each.
>
>How much of the megabyte of space have you ACTUALLY used?
>
>A meg of EPROM seems insane to me for a low-cost SBC.
>
One application is a CP/M romdisk, multiple program loader.
Allison
