21 Nov
1998
21 Nov
'98
11:40 a.m.
harrumph; typical clueless non-computer type that thinks any old computer is
worth plenty. there's a guy at an established flea market that tries to get
the same price out of old machines. i bought a northgate 386/20 from a guy at
work and even got the great northgate keyboard too for only $20!
heh, you oughta go back to the guy and ask him if he'd be willing to buy
comparable 386 and 486 models for half his asking price. i could find some
pretty cheap machines and make profit off him!
In a message dated 11/21/98 8:25:08 PM US Eastern Standard Time,
transit(a)primenet.com writes:
They had a no-name 386 clone, complete with color
monitor, in working
condition for $175, and a 486, no monitor, unknown condition (most likely
working though) for $250.
Seemed very high to me, as I've picked up working 8080 PC's and XT's for
under $20. . .
(They did also have an old Mac 128, but I didn't inquire about it, as
those are not exactly rare either)
20 Nov
20 Nov
4:06 p.m.
I just shipped a 640k Compaq SLT/286 with a 42mb IDE HDD and floppy for $76 plus
an additional $20 for a 4mb add-in SIMM (expensive and odd SIMM usually) to
Arizona, and the buyer was more than pleased with it since he named the price by
bidding that high on it (eBay, where else). He even went for priority shipping
which brought the total in the area of $115.......no problems and he loves it. He
is presently uiing it for the wordprocessor in Windows 3.11 to write manuscripts
I believe.
SUPRDAVE(a)aol.com wrote:
harrumph; typical clueless non-computer type that
thinks any old computer is
worth plenty. there's a guy at an established flea market that tries to get
the same price out of old machines. i bought a northgate 386/20 from a guy at
work and even got the great northgate keyboard too for only $20!
heh, you oughta go back to the guy and ask him if he'd be willing to buy
comparable 386 and 486 models for half his asking price. i could find some
pretty cheap machines and make profit off him!
In a message dated 11/21/98 8:25:08 PM US Eastern Standard Time,
transit(a)primenet.com writes:
> They had a no-name 386 clone, complete with color monitor, in working
> condition for $175, and a 486, no monitor, unknown condition (most likely
> working though) for $250.
>
> Seemed very high to me, as I've picked up working 8080 PC's and XT's
for
> under $20. . .
>
> (They did also have an old Mac 128, but I didn't inquire about it, as
> those are not exactly rare either)
>
22 Nov
22 Nov
3 a.m.
New subject: Northgate Keyboards (was Old 386 and 486 pc's)
At 08:40 PM 11/21/98 -0500, SUPRDAVE(a)aol.com wrote:
harrumph; typical clueless non-computer type that
thinks any old computer is
worth plenty. there's a guy at an established flea market that tries to get
the same price out of old machines. i bought a northgate 386/20 from a guy at
work and even got the great northgate keyboard too for only $20!
heh, you oughta go back to the guy and ask him if he'd be willing to buy
comparable 386 and 486 models for half his asking price. i could find some
pretty cheap machines and make profit off him!
A bit of a tangent ...
I have two old Northgate keyboards that I can't even think about parting
with. So they've come along as the basic box has been replaced several
times. But I have a problem with what I think is switch bounce. Pressing a
key frequently generates two or three of the letter/symbol. This is not the
normal 'repeat' thing, but occurs instantly.
Has anyone tracked down this problem???
Jan Skirrow
Duncan, British Columbia, Canada
24 Nov
24 Nov
12:59 a.m.
At 08:40 PM 11/21/98 EST, SUPRDAVE(a)aol.com wrote:
harrumph; typical clueless non-computer type that
thinks any old computer is
worth plenty. there's a guy at an established flea market that tries to get
the same price out of old machines.
I live in a tiny town of 6,000, 30-40 miles from the nearest metro
areas, and the small mom-and-pop computer store here routinely throws
away 486 and even slow or odd Pentium machines. They often grab
the useful RAM or CPUs and cards from them, but once you're down
to 386s, they'll often leave the parts. These machines are trade-ins
or unclaimed repairs. Sheesh, I must have a dozen or two in the
basement.
I can't imagine what the situation must be like at computer stores in
the "big city." They must toss out PCs by the dumpster-full. Even if
they refused trade-ins, there must be a lot of good finds because of
the "it's easier and cheaper to replace it than fix it" mentality.
- John
5:47 a.m.
New subject: Call for final Elf99 design input
I am cranking along with the capture of the Elf99 design (on OrCAD for DOS,
a 10-year-old program, no less). I wanted to throw out what I have
descided on and ask for suggestions on what is not set in stone.
The Elf99 will consist of the following:
o Double-sided PCB, approx 6"x8" (same as the Quest Elf design)
o CDP1802 processor with discrete CMOS support logic.
o Socket for 6116/62256 SRAM
o EPROM enable switch.
o Circuit to ghost EPROM at $0000 until first address access at $8000
o Socket for 2764/27256 EPROM.
o Dual TIL 311 hex latching displays accessible as output port 4
when in run mode.
o 8 toggle switches for data entry in load mode, accessible as
input port 4 when in run mode.
o Seperate LOAD and RUN switches to permit the user to set the
computer to "reset", "wait", "load" and "run"
modes.
o A memory protect switch to allow reviewing the contents of
RAM without changing it.
o An "Enter" pushbutton to DMA the switch register into RAM when in
load mode, that can be sensed on EF4 when in run mode.
Options under consideration:
o Sockets for two 1822/2101 256x4 SRAMs, the same style used by
the original Elf.
o A 1851 programmable input/output port -or- a pair of 4508 latches
wired as one input and one output port (as in the COSMAC VIP)
o A 1854 UART
o A protoyping area of .1" spaced plated-through holes, nominally
a few inches long by one or two inches wide.
o Either a dual 4042 address latch or a single 4508 latch. One or
the other is needed to implement more than 256 bytes of memory.
This would be optional in a machine built with dual-256x4 SRAMs.
o A pre-programmed 27256 with a "library" of simple programs
(Accessible by enabling the ROM switch, setting the program
number in the switch register, then setting the control switches
to "run").
Did I miss anything? Any other suggestions? I will not be including space
for an 1861 because I have been entirely unable to locate a source.
Do we still have any interested parties? I have saved the addresses of
all who have initially expressed interest, so I only really need to know if
these features are attracting people or putting them off.
-ethan
8:16 a.m.
New subject: Call for final Elf99 design input
Is the graphics chip right out? That was the most fun part of my super-elf.
I still have the monochrome display I used with it...
--Chuck
At 02:47 PM 11/24/98 -0500, you wrote:
I am cranking along with the capture of the Elf99 design (on OrCAD for DOS,
a 10-year-old program, no less). I wanted to throw out what I have
descided on and ask for suggestions on what is not set in stone.
The Elf99 will consist of the following:
o Double-sided PCB, approx 6"x8" (same as the Quest Elf design)
o CDP1802 processor with discrete CMOS support logic.
o Socket for 6116/62256 SRAM
o EPROM enable switch.
o Circuit to ghost EPROM at $0000 until first address access at $8000
o Socket for 2764/27256 EPROM.
o Dual TIL 311 hex latching displays accessible as output port 4
when in run mode.
o 8 toggle switches for data entry in load mode, accessible as
input port 4 when in run mode.
o Seperate LOAD and RUN switches to permit the user to set the
computer to "reset", "wait", "load" and "run"
modes.
o A memory protect switch to allow reviewing the contents of
RAM without changing it.
o An "Enter" pushbutton to DMA the switch register into RAM when in
load mode, that can be sensed on EF4 when in run mode.
Options under consideration:
o Sockets for two 1822/2101 256x4 SRAMs, the same style used by
the original Elf.
o A 1851 programmable input/output port -or- a pair of 4508 latches
wired as one input and one output port (as in the COSMAC VIP)
o A 1854 UART
o A protoyping area of .1" spaced plated-through holes, nominally
a few inches long by one or two inches wide.
o Either a dual 4042 address latch or a single 4508 latch. One or
the other is needed to implement more than 256 bytes of memory.
This would be optional in a machine built with dual-256x4 SRAMs.
o A pre-programmed 27256 with a "library" of simple programs
(Accessible by enabling the ROM switch, setting the program
number in the switch register, then setting the control switches
to "run").
Did I miss anything? Any other suggestions? I will not be including space
for an 1861 because I have been entirely unable to locate a source.
Do we still have any interested parties? I have saved the addresses of
all who have initially expressed interest, so I only really need to know if
these features are attracting people or putting them off.
-ethan
8:26 a.m.
New subject: Call for final Elf99 design input
Is the graphics chip right out? That was the most fun part of my super-elf.
I still have the monochrome display I used with it...
--Chuck
Do you know where to buy them? Harris does not list it, and I was not able
to turn up a source of *any* on the surplus market. It's cool toy, but
seemingly no longer available. :-(
-ethan
25 Nov
25 Nov
7:11 a.m.
New subject: Call for final Elf99 design input
o EPROM enable switch.
Where is the original PROM ?
Use a part of the EPROM constantly maped at $0000 or add an
1824 32x8 RAM ?
o Circuit to ghost EPROM at $0000 until first address
access at $8000
I still would go for a better decoding - just the high bit is to short.
Maybe there are some spare gates to use ?
And I still would like to combine the shadow and boot option.
o Sockets for two 1822/2101 256x4 SRAMs, the same
style used by
the original Elf.
Esential to be as close as possible to the original design.
o A 1851 programmable input/output port -or- a pair
of 4508 latches
wired as one input and one output port (as in the COSMAC VIP)
I would go for two 1852 Ports. They use only one adress each.
o A 1854 UART
Data transfer via Q is way more fun (Hi Alison :).
And since we don't need high speed transfer (2400 is ridicoulous i
we can do 110 :) a complete software solution is a great thing to do.
o Either a dual 4042 address latch or a single 4508
latch. One or
the other is needed to implement more than 256 bytes of memory.
This would be optional in a machine built with dual-256x4 SRAMs.
Isn't there already a fiting latch in the 18xx family ? (1883 ??)
I would prefer 18xx chips prior to all others.
o A pre-programmed 27256 with a "library"
of simple programs
(Accessible by enabling the ROM switch, setting the program
number in the switch register, then setting the control switches
to "run").
Did I miss anything? Any other suggestions? I will
not be including space
for an 1861 because I have been entirely unable to locate a source.
But maybe space for two (or better four) 1855 MDU. Playing with such
a beast is suposed to be a lot of fun. The same might be true for a
1879 RTC. These parts are still available.
Also I would like to have an additional 1852 (i/o selectable via
switch - but I only need output) to add an LCD display. Thera
are some real cheap displays available with a paralell ASCII
input - less than 25 USD for 16x2 characters.
Do we still have any interested parties? I have saved
the addresses of
all who have initially expressed interest, so I only really need to know if
these features are attracting people or putting them off.
Let's get serious, the Elf99 is not suposed to be the real thing, used for
real applications. It's just for the fun of doing it, and experimenting with
unusual concepts (unusula from todays view). When ever you want to
do real apps, any 6504+6532 or 68xx singlechiper will be more relevant.
Servus
Hans
--
Ich denke, also bin ich, also gut
HRK
7:07 a.m.
New subject: Call for final Elf99 design input
o EPROM enable switch.
Where is the original PROM ? Use a part of the EPROM constantly maped at $0000 or
add an
1824 32x8 RAM ?
I don't get this.
o Circuit to
ghost EPROM at $0000 until first address access at $8000
I still would go for a better decoding - just the high bit is to short.
Maybe there are some spare gates to use ? And I still would like to combine the shadow and boot
option.
If I did not convey that properly, I'm sorry. Yes, the boot option
is always there because it's software. The hardware echoes the ROM at
$0000 and $8000 when the PROM enable switch is on, and the act of reading
a valid ROM address (high memory) resets the flip flop, restoring the
more normal RAM at $0000 and ROM at $8000. If you make the first two
instructions INP 4 and PHI 0 (your suggestion), you get the ROM bank select
feature that you originally proposed.
o Sockets for
two 1822/2101 256x4 SRAMs, the same style used by
the original Elf.
Esential to be as close as possible to the original design. o A 1851
programmable input/output port -or- a pair of 4508 latches
wired as one input and one output port (as in the COSMAC VIP)
I would go for two 1852 Ports. They use only one adress each. o A 1854 UART
Data transfer via Q is way more fun (Hi Alison :).
And since we don't need high speed transfer (2400 is ridicoulous i
we can do 110 :) a complete software solution is a great thing to do. o Either a
dual 4042 address latch or a single 4508 latch. One or
the other is needed to implement more than 256 bytes of memory.
This would be optional in a machine built with dual-256x4 SRAMs.
Isn't there already a fiting latch in the 18xx family ? (1883 ??) I would prefer 18xx chips prior to all others.
I'm willing to consider 18xx chips, but they are each several dollars,
while CMOS 4xxx chips are under a buck each, even in small quantities.
But maybe space for two (or better four) 1855 MDU.
Playing with such
a beast is suposed to be a lot of fun. The same might be true for a
1879 RTC. These parts are still available.
I still have yet to hear why the 1855 Multiply/Divide Unit is worth
the real estate. Sure, it's a neat chip, but unless it has a purpose,
I can't see including it.
The 1879 Real Time Clock might be neat, but certainly an optional part.
Also I would like to have an additional 1852 (i/o
selectable via
switch - but I only need output) to add an LCD display.
There are some real cheap displays available with a
paralell ASCII
input - less than 25 USD for 16x2 characters.
I have several. BG Micro and other places sell used 20x4 and 16x2 modules
for $2 to $7. I must say that I hadn't considered that as an optional
peripheral. It might be worth laying out a 14 pin connector off of
the output port for that purpose.
Let's get serious, the Elf99 is not suposed to be
the real thing, used for
real applications. It's just for the fun of doing it, and experimenting with
unusual concepts (unusula from todays view). When ever you want to
do real apps, any 6504+6532 or 68xx singlechiper will be more relevant.
Well... I wouldn't call a 6504/6532 board "relevant". Fun, probably, but
not current stuff. Fun this is, but if it isn't at least passingly
practical, nobody can do anything with it. I never really used my Elf
because I had no I/O beyond the Q LED and the switches. The main reason
for designing the Elf99 is to satisfy a 20-year-old desire to have a
"useful" Elf, and to capitalize on the present wave of nostalgia to
make a PCB cost-effective. I could always just bang out a single board
for myself with the iron-on transfers, but that's so much work that I'd
rather make something that I can share with a wider audience. It's risky
to consider putting up a few thousand dollars on a replica of a classic,
but if I maximize the appeal of the standard I/O ports, I'm likely to sell
a few dozen. If I can't sell 60, I can't afford to invest in 100 PCBs.
12:30 p.m.
New subject: Santa Ana ACP Store
I took a trip down to Los Angeles today, and stopped by the Santa Ana ACP
store. As I looked around the store, there were some classics sitting on
the shelf. Among the many computers were the IMSAI, Heathkit Analog
Computer (EC1?), Compal, Lisa 2, Morrow, Thinker Toys, and a bunch of
others. These were not for sale, and I talked to the president, Dave
Freeman. He was unaware of this list, something I told him I would rectify
:). It sounds like he is planning an Internet Museum, and won't keep these
computers on display as it sounds like he needs the room for his business.
Hopefully, he will join the list!
12:46 p.m.
New subject: Santa Ana ACP Store
On Wed, 25 Nov 1998, Marvin wrote:
I took a trip down to Los Angeles today, and stopped
by the Santa Ana ACP
store. As I looked around the store, there were some classics sitting on
the shelf. Among the many computers were the IMSAI, Heathkit Analog
Computer (EC1?), Compal, Lisa 2, Morrow, Thinker Toys, and a bunch of
others.
He's got at least three Altairs; weren't they on display? They just
compressed their floor space about a month ago. His machines have been on
display for a long time, but they were sitting in heaps last time I was
there. (Yes, that's an EC-1.)
-- Doug
1:07 p.m.
New subject: Santa Ana ACP Store
Doug Yowza wrote:
On Wed, 25 Nov 1998, Marvin wrote:
He did mention that he had three Altairs, and I think one was on display.
The computers were on the top shelf along one wall, and in a display cabinet
on the other side of the room. It was fun talking to someone else who
enjoys collecting old computers!
I took a trip down to Los Angeles today, and
stopped by the Santa Ana ACP
store. As I looked around the store, there were some classics sitting on
He's got at least three Altairs; weren't they on display? They just
compressed their floor space about a month ago. His machines have been on
26 Nov
26 Nov
4:43 a.m.
New subject: Call for final Elf99 design input
o EPROM enable switch.
Where is the original
PROM ? Use a part of
the EPROM constantly maped at $0000 or add an
1824 32x8 RAM ?
I don't get this. > > o Circuit to ghost EPROM at $0000 until
first address access at $8000
> I still would go for a better decoding - just the
high bit is to short.
> Maybe there are some spare gates to use ?
Wait a minute. We have been having an extensive
offline conversation
and you said that 32K of RAM and 32K of ROM is enough. It can be more or less
of either, at a cost of gates and complexity.
Yep, but AFAIR I never taked about the starting address - my fault.
I assumed a varable starting adress.
Going over the Quest design, I managed to eliminate a
4049 by redesigning
the PROM area - the original used several inverters and NANDs to decode A6-A8.
:)) That sounds like fun
> And I still would like to combine the shadow and
boot option.
If I did not convey that properly, I'm sorry.
Yes, the boot option
is always there because it's software. The hardware echoes the ROM at
$0000 and $8000 when the PROM enable switch is on, and the act of reading
a valid ROM address (high memory) resets the flip flop, restoring the
more normal RAM at $0000 and ROM at $8000. If you make the first two
instructions INP 4 and PHI 0 (your suggestion), you get the ROM bank select
feature that you originally proposed.
Ahh ok. Hmm so if we want to use the 'switch-boot' a RAM based function
can never be used ? or do you only map the first 256 (or less) bytes of the
EPROM to $0000 ?
> > o Sockets for two 1822/2101 256x4 SRAMs,
the same style used by
> > the original Elf.
> Esential to be as close as possible to the original design.
One vote for, several against or abstaining.
Adding two sockets wouldnt be a big thing I guess, but one could build
a system with only the 256 Bytes of storage :)
> > o A 1851 programmable input/output port
-or- a pair of 4508 latches
> > wired as one input and one output port (as in the COSMAC VIP)
> I would go for two 1852 Ports. They use only one adress each.
I'm not inclined to do dual 1852's. We you
and I have discussed, the 1851
uses three ports, the switch/display is another port, leaving three left
over. While ports are scarce, they are no so scarce as to overshadow the
benefits of a bit-programmable I/O port.
The space taken up by two 40 pin chips is a bit much
when I can implement
two cheap ports (one in and one out) with octal latches.
You're right.
What about adding a latched solution for all parallel ports like mentioned in
one of the App notes (I think it was with one of the latches).
> > o A 1854 UART
> Data transfer via Q is way more fun (Hi Alison
:).
> And since we don't need high speed transfer (2400 is ridicoulous i
> we can do 110 :) a complete software solution is a great thing to do.
I have no problems in principle with a software UART,
but I do have
something to say about the speed. 2400 baud is *not* a ridiculous
speed, especially if you want to talk to an external device that has
a fixed clock, say, a serial-to-LCD board.
Serious, this was inteded as a joke - Even with software controll
2400 Bd should be no problem at all - and for the LCD, I would realy
like to use one of these ASCII input LCDs
The other issue with a
software UART is timing. If you use a hardware UART, it needs a
crystal of a particular frequency, but the CPU does not. You can then
"clock chip" the 1802 up (to use a Mac term) and not recode your serial
routines.
Right.
> > o Either a dual 4042 address latch or a
single 4508 latch. One or
> > the other is needed to implement more than 256 bytes of memory.
> > This would be optional in a machine built with dual-256x4 SRAMs.
> Isn't there already a fiting latch in the
18xx family ? (1883 ??)
The 1883 is a *7* bit latch with built-in decoders.
We need no decoder
because the low 15 bits of the full address bus are going to each the
ROM and RAM sockets. There are no individual memory chips to select.
The 1883 is a great chip if you want to use several 6116's, for example.
Shure, again right. I mixed up two ideas I had.
Anyway, if we use your 32K RAM plus 32K ROM design, I thougt
about adding a kind of CS unit to provide several CS signals for adding
various memory or memory maped areas. For example if we supply
8 CS lines for 8 8K areas, one could bild a system like:
2K EPROM at $8000 (needed to perform the 'boot') and
256 Bytes RAM at $2000 and a memory maped
1851 at $4000 ... or some other configurations.
> I would prefer 18xx chips prior to all others.
I'm willing to consider 18xx chips, but they are
each several dollars,
while CMOS 4xxx chips are under a buck each, even in small quantities.
My view of the Elf99 is more fun and hobby than real applications.
Playing with unusual components and using 'real' 18xx stuff is
part of this flair. A 4xxx based I/O is just less 'sexy' than a 185x.
Its like with some of our vintage equipment - connecting a Terminal
to an Altair gives a diferent feeling than to any 12 MHz 64180 system,
even when running the same CP/M and the same Wordstar...
> But maybe space for two (or better four) 1855
MDU. Playing with such
> a beast is suposed to be a lot of fun. The same might be true for a
> 1879 RTC. These parts are still available.
I still have yet to hear why the 1855 Multiply/Divide
Unit is worth
the real estate. Sure, it's a neat chip, but unless it has a purpose,
I can't see including it.
Gee the purpose is to multiply and divide - what else :-)
If you just think about the real world usability of an Elf99,
we shold stop it and go for a 80188 design of an equal
level (I like the 8018x CPUs)-
The 1879 Real Time Clock might be neat, but certainly
an optional part.
Even when only thinking about real world apps, a RTC is
essentoil for a lot of controll or household things (just try
to count all devices in your home that utilizes a clock,
visible or not - from microwave to VCR ...).
And for both chips (MDU and RTC), I don't want them to
be esential - just optional. And I think they offer a lot
of possible usages (what about a Elf Basic using the MDU
for speed ?).
(BTW: Just look at the 'front panel' thread - a MDU would offer
a lot of new and excitieing lights :)
> Also I would like to have an additional 1852 (i/o
selectable via
> switch - but I only need output) to add an LCD display.
> There are some real cheap displays available with
a paralell ASCII
> input - less than 25 USD for 16x2 characters.
I have several. BG Micro and other places sell used
20x4 and 16x2 modules
for $2 to $7. I must say that I hadn't considered that as an optional
peripheral. It might be worth laying out a 14 pin connector off of
the output port for that purpose.
USD 2 for a 16x2 (or USD 7 for a 20x4) including controller ?
Thats pretty cheap. If this is true, a 20x4 should be included
for shure. A LCD without controller is not usefull, since a permanent
scann to support output counters the basic static Design.
> Let's get serious, the Elf99 is not suposed
to be the real thing, used for
> real applications. It's just for the fun of doing it, and experimenting with
> unusual concepts (unusula from todays view). When ever you want to
> do real apps, any 6504+6532 or 68xx singlechiper will be more relevant.
Well... I wouldn't call a 6504/6532 board
"relevant". Fun, probably, but
not current stuff. Fun this is, but if it isn't at least passingly
practical, nobody can do anything with it.
6504+6532 gives a great system for controll apps of any kind, and is
comparable to most single chip CPUs (128 Bytes RAM, 2 I/O ports,
Timers) , so it is still relevant, and fits for practical use anything you
can do with the Elf99 -ok, maybe use a 6502 instead the 6504
(And my personal choise is still a 80188 :).
I never really used my Elf
because I had no I/O beyond the Q LED and the switches. The main reason
for designing the Elf99 is to satisfy a 20-year-old desire to have a
"useful" Elf, and to capitalize on the present wave of nostalgia to
make a PCB cost-effective. I could always just bang out a single board
for myself with the iron-on transfers, but that's so much work that I'd
rather make something that I can share with a wider audience. It's risky
to consider putting up a few thousand dollars on a replica of a classic,
but if I maximize the appeal of the standard I/O ports, I'm likely to sell
a few dozen. If I can't sell 60, I can't afford to invest in 100 PCBs.
With to much usefullnes, you might reduce the potential interest.
The apeal lies in having an Elf like computer, but with all the fancy
stuff to draw fun from programming and playing. Thats one main
reason why I suggestet the library and the library boot - ready made
simple applications to play with, to demonstrate to friends and family
members. I bet, everyone of us has sometimes recived a dumb look
when he was explaining how beautiful some function or programm is
and how usefull ...
So my idea of the Elf99 is an easy to use experimentation / training
kit with a lot of interesting features - NOT any kind of very usefull high
powered controller. Something to learn about a microcomputer for
children, to show to friends and relatives, a brain game to try (almost)
all things belonging to a computer - and the MDU is just a part of this
idea - pointing to two (or four) chips and tell someone thats the 'super
high integrated calculator' thing and show _real_ programming of the
I/O of numbers is something complete different than pointing to a pentium
class chip and say 'oh, and in there is a FPU for calculations' or to
add some FPU instructions in your programm (remember, with the
help of a 5 byte programm you could even show them how to feed
the MPU and how to retrieve the result via switches and the TIL 311).
In fact, if the design is a in this direction I plan to use two of them
for children in the age of 11 and 14.
Gruss
Hans
--
Ich denke, also bin ich, also gut
HRK
4 Dec
4 Dec
4:05 a.m.
New subject: Call for final Elf99 design input
The idea is to map a part of the EPROM permanently to
$0000-$001F
as replacemet for the original prom, or to suply a 32x8 RAM (like the
1824, since we want to use as much 'original' Harris stuff as possible
Using as much Harris stuff as possible is not one of my design goals.
Simplicity is. At the moment, the only Harris part may be the 1802
mostly due to cost. The Harris stuff is between $5 and $10 per chip.
Yep, but AFAIR I never taked about the starting
address - my fault.
I assumed a varable starting adress.
That was the gist of my questions. It appears that we were using terms that
the other was not fully understanding. The term "memory space" that I used,
refers to a region of memory that is designed to contain something, but may
or may not be full. For example, a 4K PET has 32K of RAM address space, but
4K of RAM. It's trivial to add another 28K of RAM, not so trivial to add
RAM outside of that 32K address space. A 68000 smart serial card I used to
make had the 16Mb divided into 4 address spaces: RAM, I/O, shared memory (it
was a DMA card on a PDP-11) and ROM. Even though no card ever had more than
2Mb of RAM (the oldest card had 32K of 2114!), all of the later cards had 4Mb
of the memory map blocked out for RAM.
It is easy to divide the memory space into 1/2 RAM and 1/2 ROM. It's harder
to divide it into 3/4 RAM and 1/4 ROM. It's even harder to divide it into
3/4 RAM, 1/8 ROM and 1/8 memory-mapped I/O, and it's hardest of all to make
the division user configurable. A 48K Elf might be cool, but none of the
ancient software knows much more than about 4K, leaving plenty of the
intended 32K left for new stuff. Besides, I want to stick with one RAM chip
and one ROM chip, for simplicity.
Ahh ok. Hmm so if we want to use the
'switch-boot' a RAM based function
can never be used ? or do you only map the first 256 (or less) bytes of the
EPROM to $0000 ?
No... the entire ROM maps at $0000 and $8000 until the first time that A15
gets set, then the flip-flip clears and RAM banks in at $0000 and ROM remains
at $8000. This is easy to implement and fairly clean. No I/O address needs
to be hung up as in the VIP design (62).
Adding two sockets wouldnt be a big thing I guess, but
one could build
a system with only the 256 Bytes of storage :)
Technolgically speaking, it's trivial. The issue is real estate. If I have
to make the board bigger, the cost goes up. I'm thinking about designing
and releasing a design for a piggyback board to plug into the 6116/62256
socket to adapt a pair of 1822/2101's. I wouldn't *make* that board, but
anyone who wanted to use 256x4 RAMs should be able to make their own.
The space
taken up by two 40 pin chips is a bit much when I can implement
two cheap ports (one in and one out) with octal latches.
You're right. What about adding a latched solution for all parallel
ports like mentioned
in one of the App notes (I think it was with one of the latches).
If I understand what you are suggestion, Allison suggested that, too. You mean
decoding additional secondary ports from a primary port, yes? The reasons
not to do it are a) increased complexity of design and b) increased complexity
of programming. I have not utterly dismissed it, but neither am I
overwhelmingly convinced that it's necessary.
> > o A
1854 UART
> Data transfer via Q is way more fun (Hi
Alison :).
Serious, this was inteded as a joke - Even with software controll
2400 Bd should be no problem at all - and for the LCD, I would realy
like to use one of these ASCII input LCDs Anyway, if we use your 32K RAM plus 32K ROM design, I
thougt
about adding a kind of CS unit to provide several CS signals for adding
various memory or memory maped areas. For example if we supply
8 CS lines for 8 8K areas, one could bild a system like:
2K EPROM at $8000 (needed to perform the 'boot') and
256 Bytes RAM at $2000 and a memory maped
1851 at $4000 ... or some other configurations.
Ack! Too complicated. I'm after *simple* here. While your concept
here is very powerful,
My view of the Elf99 is more fun and hobby than real
applications.
Playing with unusual components and using 'real' 18xx stuff is
part of this flair. A 4xxx based I/O is just less 'sexy' than a 185x.
It is and it isn't, depending on the nature of the playing. After all,
you can't stick a logic probe inside a 185x chip. You *can* watch a 4308
latch the data and observe how a parallel port works, if you care to.
Besides, the 1852 is nearly 10 times the cost of the 4308.
Its like with some of our vintage equipment -
connecting a Terminal
to an Altair gives a diferent feeling than to any 12 MHz 64180 system,
even when running the same CP/M and the same Wordstar...
Yes, but even a real RCA product, the VIP, used 4308 latches for PIO.
I still have
yet to hear why the 1855 Multiply/Divide Unit is worth
the real estate. Sure, it's a neat chip, but unless it has a purpose,
I can't see including it.
Gee the purpose is to multiply and divide - what else :-) If you just think about the real world usability of an
Elf99,
we shold stop it and go for a 80188 design of an equal
level (I like the 8018x CPUs)-
But the Intel architecture isn't sexy like the 1802. You can't build
a ROMless 8018x system with 256 bytes of RAM. As complex as the Elf99
is turning out, I know it can be partially populated to produce a very
good approximation of the original Quest design (leave off the address
latch and all I/O except the Q LED). Someone wishing to build the
whole design can stuff every crevice with parts and have an Elf beyond
our wildest dreams of 1977.
And for both chips (MDU and RTC), I don't want
them to
be esential - just optional. And I think they offer a lot
of possible usages (what about a Elf Basic using the MDU
for speed ?).
Optional isn't the issue. The cost of the board space is. I've already
planned on lots of optional stuff (PIO, UART, more than 256 bytes of RAM).
I'm not opposed to optional things. I am just trying to give as much
expansion as $99 will allow. If the board costs more, it loses its
audience.
(BTW: Just look at the 'front panel' thread -
a MDU would offer
a lot of new and excitieing lights :)
Too complicated for a $99 design.
USD 2 for a 16x2 (or USD 7 for a 20x4) including
controller ?
If by controller you mean a Hitachi 48440 or similar chip that sits between
the raw LCD and provides the user with a font and parallel (4 or 8 bit)
interface, then yes. $2 to $9 is a typical range, depending on new or
used or backlight or not.
Thats pretty cheap. If this is true, a 20x4 should be
included
for shure. A LCD without controller is not usefull, since a permanent
scann to support output counters the basic static Design.
I've got a 20x4 on my Linux box (as I said). I chose to spend $24 extra
(I scrounged the power supply and box) to keep the programming from a UNIX
machine simple. There is no such requirement on a toy board.
The apeal lies in having an Elf like computer, but
with all the fancy
stuff to draw fun from programming and playing. Thats one main
reason why I suggestet the library and the library boot
No argument about the library boot. I spent lots of time entering in
games from the VIP manual (I still have the tape!)
So my idea of the Elf99 is an easy to use
experimentation / training
kit with a lot of interesting features - NOT any kind of very usefull high
powered controller. Something to learn about a microcomputer for
children...
So far we are in agreement. I don't expect anyone to buy this and build
it into an Internet Coke machine or anything.
..and the MDU is just a part of this idea
In the abstract, I agree, but I still see no practical use for the MDU except
as an expensive, flashy toy that would only appeal to a few people (less than
5%). I'm shooting for 80% or 90% audience acceptance for a feature. So
far, that's 8 bits in, 8 bits out and some sort of serial port (plus the
required switches, displays and Q).
In fact, if the design is a in this direction I plan
to use two of them
for children in the age of 11 and 14.
They would be a good audience. I got my hands on a Quest Elf when I was 11.
It nand the PET profoundly affected my life and career path.
-ethan
9298
days inactive
9311
days old
13 comments
9 participants
participants (9)
-
cmcmanis＠mcmanis.com -
dma＠islandnet.com -
erd＠infinet.com -
Hans.Franke＠mch20.sbs.de -
jfoust＠threedee.com -
marvin＠rain.org -
rhblake＠bigfoot.com -
SUPRDAVE＠aol.com -
yowza＠yowza.com