Subject: Re:Restoration: how far should it go??

From: "Michael Holley" <[email-masked]>
Date: Sun Jun 15 17:39:00 2003

>         How much do people think is too much restoration???

I try to get my machines running as they would have been in their prime.
This includes making the common upgrades that most users would have done.
Since I am restoring kits, there was wide variation in assemble quality. If
I have or can find the correct parts I am just finishing the assemble 25
years later.  (I am talking about adding a capacitor or a minor cut and
jumper. Not increasing the memory by tacking RAM chips on top of the
original ones.)

I want the machine to work, even if I have to replace parts. I restored a
SWTPC TV Typewriter that had been very poorly assembled in the 1970s by
stripping the boards bare. (This is not the first choice procedure.) I was
able to find accurate replacements for almost all of the parts.
http://www.swtpc.com/mholley/CT_1024/Restore/CT1024_Restore.htm

I also build new upgrade boards for SWTPC 6800 computers. Some of these use
current production parts and some use historical parts. These can added to a
system and removed without damage. (I sell copies of some of my upgrades but
I make them for my own use. Which is a good thing because I will never
recover my cost.)
http://home.attbi.com/~swtpc6800/new_stuff.htm

Sometimes a hand wired board is a accurate example of what the original
owners would have used.
http://www.swtpc.com/mholley/QRC_Proto/32kMemoryIndex.htm

These upgrades allow the base level product to be upgraded to a full
featured version so you can run the vintage software.

Another area of restoration is documentation. I have been scanning
documents, converting them to text, then creating PDF files for the web. I
correct the typographical errors in the originals and add corrections. I
don't try to maintain the exact format or pagination. I do identify major
changes that I make.

I have been taken to task of not preserving the original documents with all
of the errors!

Michael Holley
www.swtpc.com/mholley

---

From: jamesd <[email-masked]>
Date: Sun Jun 15 17:39:10 2003

> jumper. Not increasing the memory by tacking RAM chips on top of the

I see you have higher standards than IBM, for a while after the AT was 
released they sold ram that was two chips piggy backed so they could get more 
ram on the board. 

> current production parts and some use historical parts. These can added to
> a system and removed without damage. (I sell copies of some of my upgrades
> but I make them for my own use. Which is a good thing because I will never
> recover my cost.)

---

From: "Eric Smith" <[email-masked]>
Date: Sun Jun 15 17:39:39 2003

> released they sold ram that was two chips piggy backed so they could get

I don't think that's a sign of poor standards at IBM.  The IBM parts were
specifically engineered to be stacked.  They didn't just take normal DIP
RAMs, stack them up, and have some tech hand solder them together.

The stacked DIP packages were a replacement for the earlier Mostek dual
RAM packages that had two ceramic leadless chip carriers soldered to a
ceramic DIP substrate.  The stacked DIPs were less expensive to
manufacture because they could mold both packages and simply use longer
lead frames for the top, but still fundamentally use their normal plastic
DIP production flow.  The only additional manufacturing step was to
ultrasonically weld the leads together.  (At least, I think that's how
they did it.  I'm not 100% certain, and I don't have any close at hand
to examine.)

Note that the two stacked parts were bonded out with a slightly different
pinout, since the RAS and CAS strobes had to be on different pins.
However, since the top DRAMs were being bonded to a special lead frame
anyhow, this was not a big issue.

Both the CLCC on substrate and the factory-stacked DIPs were actually
quite reliable.  Until ZIPs, SIPPs, and DIMMs were invented, that was
the highest packaging density in common usage for RAM.

---

From: Jim Davis <[email-masked]>
Date: Sun Jun 15 17:39:49 2003

Eric Smith wrote:

><snip>
I thought one DIP had an inverted CS, Though I might be wrong. I did the 
stacked thing on my atari 400,
Stacked 8K chips to get 16K. But that was in 82 and the atari H/W 
manuals are in the garage.
Jim Davis.

---

From: "Fred Cisin (XenoSoft)" <[email-masked]>
Date: Sun Jun 15 17:40:49 2003

> released they sold ram that was two chips piggy backed so they could get
> more ram on the board.

If you won't piggyback chips, then how would you recommend implementing
lower case on a TRS-80 model 1?  
Or getting enough RAM in the ORIGINAL coco? (before they changed the board
to support 64K/32K chips)

---

From: [email-masked] (Tony Duell)
Date: Sun Jun 15 17:41:20 2003

> jumper. Not increasing the memory by tacking RAM chips on top of the

It depends. I often _will_ do modifications, especially if such 
modifications were common when the machine was in normal use (and 
remeber some 'official' mods involved piggybacked ICs). But I make it 
clear that it _is_ a modification (e.g. if I am modifying a DEC backplane 
full of yellow wires, I'll do the mod in red wire). 

I also most certainly make use of prototyping areas on PCBs :-). I 
discovered, for example, there are enough spare IC locations on the PERQ 
OIO board to fit the QIC 02 interface (which was only ever made as a 
wire-wrapped prototype anyway AFAIK). Therefore my OIO board is possibly 
the only ether-can-tape (ethernet, Canon laser printer, QIC02 tape) 
around... 

> I make them for my own use. Which is a good thing because I will never

I often build add-on boards/modules for classic computers. I like to make 
them in a way that was at least _possible_ when the machine was in normal 
use (so no SMD parts in a 1970s minicomputer, no FPGAs, etc). But 
sometimes I break those rules. If it's a plug-in card it can be removed 
later anyway...

-tony

---

From: [email-masked] (Tony Duell)
Date: Sun Jun 15 17:41:39 2003

> released they sold ram that was two chips piggy backed so they could get more 

Hmm.. The oriignal PC/AT motherboard did have piggybacked RAMs, but it 
wasn't an IBM kludge. Those were special RAM chips (the pinouts were 
strange, with pin 1 actually used for something and the CAS/ signal from 
each chip brought out separately (I think it was CAS/)), and I don't 
think they were soldered together (looks more like ultrasonic welding to 
me). I'd assumed these were a 'standard' 128K RAM module, something like 
a Mostek part I once saw (18 pin DIL) which was a ceramic module with 2 
chips soldered on top.

Incidentally, I have seen piggybacked sockets in the catalogues. 16 pin 
ones with all pins commomed except 4 and 15 (RAS/ and CAS/ for normal 
DRAMs IIRC) and 28 pin ones with all pins commoned except 20 (CS/ for a 
JEDEC SRAM or EPROM). Interesting idea...

-tony

---

From: "Zane H. Healy" <[email-masked]>
Date: Tue Jun 17 09:44:30 2003

>This includes making the common upgrades that most users would have done.

Me, I like "Hotrodding" them, it's fun to see just how far past the norm you can take a system :^)  My PDP-11/73 is a killer system, and probably one of the better outfitted ones around (eventually I want to replace the CPU with either a /93 or a nice fast Mentec CPU).  My Amiga 3000 is pretty decked out as well, though I've not felt I could justify the Accelerator upgrade that I would like to do for it.  Another system I'd love to "Hotrod" would be one of my
Apple ][gs's, not that I mess with Apple 2's anymore.

			Zane

-- 
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| Zane H. Healy                    | UNIX Systems Administrator |
| [email-masked] (primary)    | OpenVMS Enthusiast         |
|                                  | Classic Computer Collector |
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