please see embedded remarks below.
Dick
-----Original Message-----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Friday, August 27, 1999 1:04 PM
Subject: Re: PDP era and a question
>>
>> addressing only the comment quoted below . . .
>>
>> Really, Tony, I think you overemphasize the importance of the individual
>> user to the semiconductor manufacturers. The level of competition for
the
>> FPGA business has escalated to where the development software, previously
>> costing several K-bucks US, now costs as little as $100, and, in the case
of
>> ALTERA, is quite free. Now, that's not the complete package with all the
>> bells and whistles, but it's enough to build a device from start to
finish.
>
>You've misunderstood me...
>
>There are several points here.
>
>Firstly, it doesn't matter how cheap the software is if you can't use it.
It depends more on how you define "can't" than anything else, though.
>To run one of those 'free' development systems, I'd have to get a new PC
>that I couldn't maintain and an 'OS' that I would find unpleasant to use.
I had the same feeling when just about all the useable CAD/CAE software was
limited to VMS and UNIX. I bought and limped along with what I could get
for the PC, back then using DOS and customized drivers for the appropriate
display, which, back then, alone, cost about as much as my then new logic
analyzer. What that is, Tony, is a matter of preference. YOU have to
decide where YOU spend your money.
In yesterday's newspaper I noted that the local discount house (Best-Buy for
those who care) was offering a major-brand 350 MHz Celeron-based computer
system without monitor but with AGP video, 6.4 GB HDD, 64 MB memory, CDROM,
FDD, v.90 modem, keyboard, all for $399 US. A really nice (I recently
bought one when the "appropriate display" (19") mentioned above developed a
margin problem.) 17" monitor for $199. That means that for what I typically
earn in a couple or three days after taxes and expenses, I can buy a whole
computer system capable of doing this FPGA stuff.
I recently read that the folks who sell these FPGA's have no problem at all
giving you the necessary data to enable you to configure their parts. They
won't give you a disassembly tool or whatever that would be, but they'll
tell you enough so you can build your own configuration tools to support
their parts. They won't hold your hand and they won't debug your work, but
they will give you a spec so you don't have to buy their software or use it.
>The total cost would (instead) buy some useful physical test equipment or
>tools.
>
I bought a 20-year old 250 MHz 'scope not long ago with what that system at
Best Buy would cost. Now, I shopped for a year in order to find the thing,
but that's what I got for $600.
>
>Secondly, I like all my software to be open-source so that I can fix
>bugs. Now, I can quite understand why commercial software isn't like
>this. What I am commenting on is the fact that I _can't_ write my own
>FPGA tools if I wanted to.
>
All software is open-source if you have the dough to buy the sources. Not
all of us are willing to pay the required 6.23*10^23 bucks for what we'd
otherwise get for less than $1k for just the objects.
>
>Let me give you an example. If I want to program a PDP11 in assembler, I
>can either buy the DEC assembler (which, quite rightly, costs money), or
>I can get down the manual and either hand-assemble the code or write an
>assembler myself. I can add in whatever features I want in the latter
>case as well.
>
>With FPGA tools, you can't write your own. Manufacturers have given a
>number of reasons, most of them (IMHO) bogus as to why they won't release
>the configuration specs. But with one exception (the XC6200 series), now
>discontinued, there has never been an FPGA (or CPLD) where you can go
>from schematic/description to a finished chip without some 'undocumented'
>process. It's like having a processor where the binary opcodes are not
>documented anywhere, and where the manufacture actively prevents this
>sort of information getting out.
>
Again, it's just a matter of preference. Most people get by this hurdle
with little trouble.
>
>FWIW, I have 'hand assembled' configurations for the XC6216. It wasn't
>that hard, and writing a few simple tools would have made it a lot easier.
>
>
>>
>> I really doubt that it would turn out to be illegal to take the old 11-70
or
>> whatever schematic and essentially clone it in an FPGA, but I doubt a
clever
>> rebuilder would want to do that anyway. It might be either equally good
in
>
>You wouldn't. FPGA design is most certainly not the same as TTL-type
>design, and simply translating circuits will result in something that
>doesn't work.
>
>> The technology in FPGA's these days is such that it enables devices to
>> operate between 10 and 50 times the speed of the old TTL logic designed
in
>
>Hmmm.. A good TTL design will go at 50MHz, no trouble. FPGAs are between
>500MHz and 2.5GHz? That sounds high to me. It certainly sounds high
>compared to the real-world speeds (not what the manufacturers claim) for
>common FPGA devics. A factor of 2 or 3 up on TTL, maybe.
>
There's a brocheure lying about here somewhere from a company which offers a
XILINX look-alike which operates with delays of about half those of the
fastest XILINX, though there's some question about the universality of that
claim, but they certainly explain why their routing delays are shorter.
Prop-delays of 1ns are claimed for the combinatorial logic in several
vendors' parts, and the claim of 25 MHz for 7400-series TTL was quite
generous. It would propagate into a light load and single flops would keep
up at 25 MHz. I remember a countdown chain which generated a bunch of
system timing from a 24.576 MHz clock, which was a harmonic of nearly all
the telecom clocks as well as baud rates. That one didn't work until one
substituted 74S-series TTL. HTTL and LSTTL wouldn't do it. The clock-to-Q
of the flops just wouldn't meet the required setup times. Now, it worked
fine once we rebuilt the counter chain so it ran at half that rate. Lots of
'70's TTL MSI would work at rates in excess of 30 MHz, but only for small
circuits. You could run one shift register at that rate, but if you needed
to shift longer words, you might be in trouble. It was even worse with
counters. If you then needed to decode the outputs of a 16-bit counter . .
. you see my point, I'm sure. These same problems are encountered in
FPGA's, but the circuits whose timing is critical can be planned out in such
a way that the penalties for routing delays are minimized. What's more,
because adding a pipeline register doesn't mean putting another package on
the board, you can do that. Pipeline registers increase operating frequency
while increasing the latency. They make decoding much safer.
>-tony
>
There are packaging options which might be utilized to help you in "scoping"
out your circuit. One of many complaints I have about FPGA's is that they
have far too many pins to suit me. Well, since there are lots of pins, you
can obtain a socketable adapter for the package and then work your way
through the design, changing the "bond-out" by routing the signals you want
to compare to I/O blocks associated with otherwise unused pins. That way
you might be able to help yourself figure out strange timing effects between
internal and external signals, perhaps even allowing you to see the inner
workings at least to some extent.
The handiest package I've run into for these is the PLCC84, for which you
can obtain a socket compatible with a wire-wrap adapter. That would allow
you to do what I described above without interfering with the 40-odd signals
you might want to inject into your existing application. This same thing
might be achievable with a larger package, but I have some doubts about
making the transition from the FPGA package to a wire-wrap socket. You
might have to make an adapter PCB or buy one from Samtech or Emulation
Technology. Those get expensive.
Dick
-----Original Message-----
From: allisonp(a)world.std.com <allisonp(a)world.std.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Monday, August 30, 1999 12:03 PM
Subject: Re: FPGAs and PDP-11's
>
>> They're wide PDP-8s. Or rather, the PDP-8 is a narrow PDP-4.
>
>I know that! ;) what I don't know is all them little details I know so
>well for PDP-8.
>
>> > I would want a machine that would fit in nx4 or nx8 format parts.
>>
>> Doesn't particularly help if you're putting it in an FPGA.
>
>Why would I want to use them... &-) I was thinking interms of machine
>that work in "ttl" or maybe GALs. FPGAs want those funny sockets to hold
>all those pins and they are a bear to to probe a particular gate under a
>scope after delidding it. ;)
>
>Actually a discussion of PDP-4/7/9/15 would be of interest as those are
>thos ones I really do not know beyond trivial.
>
>Allison
>
On Monday, August 30, 1999 5:26 PM, Bill Sudbrink [SMTP:bill@chipware.com]
wrote:
> Has my subscription been dropped again?
> Sorry for the noise.
>
> Bill Sudbrink
>
>
Bill,
I have been receiving some posts but, the quanity has certainly dropped
off. The S/N ratio has been pretty high lately. That's a good thing :-)
Steve Robertson - <steverob(a)hotoffice.com>
please see embedded comments below.
Dick
-----Original Message-----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Friday, August 27, 1999 4:40 PM
Subject: Re: PDP era and a question
>> >
>> >Firstly, it doesn't matter how cheap the software is if you can't use
it.
>>
>>
>> It depends more on how you define "can't" than anything else, though.
>
>"Can't" is quite simple : I can't execute the software on that
>disk/CD-ROM on any computer that I currently own. Period.
>
>>
>[...]
>
>> In yesterday's newspaper I noted that the local discount house (Best-Buy
for
>> those who care) was offering a major-brand 350 MHz Celeron-based computer
>> system without monitor but with AGP video, 6.4 GB HDD, 64 MB memory,
CDROM,
>> FDD, v.90 modem, keyboard, all for $399 US. A really nice (I recently
>
>They're a little more in the UK, although I think I've seen similar
>machines advertised here for \pounds 399 or thereabouts.
>
>> bought one when the "appropriate display" (19") mentioned above developed
a
>> margin problem.) 17" monitor for $199. That means that for what I
typically
>> earn in a couple or three days after taxes and expenses, I can buy a
whole
>> computer system capable of doing this FPGA stuff.
>
>OK for you. Remember I can't get a job. After 'essentials', I would have
>to save for about a year to get a machine like that. And there are other
>things I put somewhat higher on my priority list as I already have plenty
>of useable computer systems for everything else I want to do.
>
Well, first of all, I think it's nice that the mfg's of these devices have
made it possible to do this work on machines costing less than a year's pay,
and if there were enough business to justify it, they'd make it possible for
you to build their devices on your HP calculator or whatever you prefer.
It's just a question of how badly you want to do it. If I didn't want to
spend the necessary money, I'd not be able to do it either. Now, I don't
know why you can't get a job. There are lots of people here in the US who
are in the same boat. If you have some physical disability, or
mental/emotional impairment, though, there are programs here and I'd be
surprised if there weren't some similar programs in the UK to "help" you get
a low-cost PC if there are any indications at all that you'd be able to
produce useful work translatable in to substantial gainful activity with it
at your disposal.
However, if you can't get a job because you categorically refuse to learn to
use the PC because you find the Microsoft OS repugnant, I'd predict you'll
remain so.
>
>Please note, I am not saying that the FPGA manufacturers should support
>all the possible choices of machine and OS. Just that I wish that _one_
>of them would provide enough information for me to support them myself.
>
The reality of the matter is that these device vendors, of whom I would
assume it could be said they're in a good position to make such a
determination, have decided that it's worth their effort to invest the
effort and money in creating support tools for the PC running Windows 9x and
not the PDP-8S or whatever, running something else. This is not my
preference either, since I like and trust DOS much more than the WINDOWS
varieties, but then, they no longer put out tools for the MAC either, not
that I'd use one even if they were free.
>>
>> I recently read that the folks who sell these FPGA's have no problem at
all
>> giving you the necessary data to enable you to configure their parts.
They
>> won't give you a disassembly tool or whatever that would be, but they'll
>
>Interesting. That's exactly the opposite of my experiences with Xilinx
>when I used the official toolkit in my last job (XC3000 and XC4000 parts
>mostly).
>
>There was a _supplied_ program that would take a configuration bitstream
>and turn it back into a CLB + interconnect map - essentially a
>disassembler. Of course turning that map into a schematic was a lot of
>work, but the 'secret' part was there.
>
>But no way would they tell us what any of the bits in the configuration
>file actually meant.
>
>I am told they might have supplied some documentation under an NDA, but
>that's no use for open-source software, of course.
>
Well, it's not likely that you'll encounter much cooperation in your effort
to convince the world to share its secrets. These days, when patents are of
no use because the market window is shorter than the delay getting to court,
the only way people can defend what they perceive to be their turf is by
keeping it "close to the vest" like a hand of cards.
>
>> >Secondly, I like all my software to be open-source so that I can fix
>> >bugs. Now, I can quite understand why commercial software isn't like
>> >this. What I am commenting on is the fact that I _can't_ write my own
>> >FPGA tools if I wanted to.
>> >
>> All software is open-source if you have the dough to buy the sources.
Not
>
.>Not really. Even if I could buy a source license, that wouldn't give me
>the right to pass the sources around. About the only way to get to do
>that is to buy the company (:-)).
>
It's absolutely open source, if that's how you want to handle it, once you
buy the right to do so. I don't mean buy a copy. I mean buy ALL the
rights. Once you've acquired all the rights, by paying for them, I doubt
you'll want to give them away by making them freely distributable.
>> all of us are willing to pay the required 6.23*10^23 bucks for what we'd
>> otherwise get for less than $1k for just the objects.
>
>Again, I am not asking for the 'official' sources. Just for the ability
>to write my own.
>
Perhaps if you inquire about obtaining those rights, you'll see what value
they are perceived to represent. Dealing with the numbers helps put things
in to prespective.
I'm surprised that there was a commonly available scf2xnf (or whatever it
was called) translator, since that essentially reverse engineered your
product for your competitor, but it would surprise me even more for the
vendor to provide you the ability to see how they've enhanced their parts if
that's reflected in their configuration files.
Nevertheless, perhaps you need to back away from your devotion to the
absolute notion of fully open source in favor of a really efficient,
particularly cost-efficient, PDP whatever you want to build. If you need to
have sources in order to fix what you consider to be an annoying bug in the
software tools with which the FPGA is to be devised, I'd point out that
noone else is able to fix it either. Sometimes it's necessary to live with
those "bugs" which annoy you most.
>
>-tony
>
<Allison wrote:
<> I'd start with a 32bit PDP-8 (just add 20 more bits on the right side).
<and in another posting:
<> Me I'd do a stretch-8 for fun. though yours sounds interesting too.
<
<A Stretch-8 would require too much time spent on hacking -8 software for m
<taste. Why not just build the equivalent of one of the DEC 18-bit family
<members (PDP-4, -7, -9, or -15), since the PDP-5 and -8 are basically a 12-
<version of the PDP-4. Then your project is at least compatible with
<something, and can run some existing software (operating system, macro
<assembler, Fortran).
Several reasons. Don't know the 18 bit machines at all. I would want a
machine that would fit in nx4 or nx8 format parts. I'd want a really
simple instruction set as that simplifies the hardware ruling out the
10, 11 and vax. So streatching an 8 is it.
Now a stretch-8 would have software as the bits added would only impact the
address field. Makeing the top 5 bits and the bottom 7 behave as the normal
8 would make code port fairly reasonable. I've always found the 8 limiting
in only one way, address space. Basically the Nova is a similar idea
stopping at 16 bits.
Allison
