6 Jan
2019
6 Jan
'19
1:19 p.m.
From: Grant Taylor
Is "byte" the correct term for 6-bits? I
thought a "byte" had always
been 8-bits.
I don't claim wide familiary with architectural jargon from the early days,
but the PDP-10 at least (I don't know about other prominent 36-bit machines
such as the IBM 7094/etc, and the GE 635/645) supported 'bytes' of any size,
with 'byte pointers' used in a couple of instructions which could extract and
deposit 'bytes' from a word; the pointers specified the starting bit, and the
width of the 'byte'. These were used for both SIXBIT (an early character
encoding), and ASCII (7-bit bytes, 5 per word, with one bit left over).
I would have blindly substituted "word" in
place of "byte" except for
the fact that you subsequently say "12-bit words". I don't know if
"words" is parallel on purpose, as in representing a quantity of two
6-bit word.
I think 'word' was usually used to describe the instruction size (although
some machines also supported 'half-word' instructions), and also the
machine's 'ordinary' length - e.g. for the accumulator(s), the quantum of
data transfer to/from memory, etc. Not necessarily memory addresses, mind -
on the PDP-10, those were 18 bits (i.e. half-word) - although the smallest
thing _named_ by a memory addresses was usually a word.
Noel
6 Jan
6 Jan
1:25 p.m.
I think it?s also telling that the IETF uses the term octet in all of the specifications
to
refer to 8-bit sized data. As ?byte? (from older machines) could be anything and is
thus somewhat ambiguous.
It *may* have been the IBM 360 that started the trend of Byte == 8-bits as the 360?s
memory (in IBM?s terms) was byte addressable and the instructions for accessing
them were ?byte? instructions (as opposed to half-word and word instructions).
TTFN - Guy
On Jan 6, 2019, at 10:19 AM, Noel Chiappa via cctalk
<cctalk at classiccmp.org> wrote:
From: Grant Taylor
Is "byte" the correct term for 6-bits?
I thought a "byte" had always
been 8-bits.
I don't claim wide familiary with architectural jargon from the early days,
but the PDP-10 at least (I don't know about other prominent 36-bit machines
such as the IBM 7094/etc, and the GE 635/645) supported 'bytes' of any size,
with 'byte pointers' used in a couple of instructions which could extract and
deposit 'bytes' from a word; the pointers specified the starting bit, and the
width of the 'byte'. These were used for both SIXBIT (an early character
encoding), and ASCII (7-bit bytes, 5 per word, with one bit left over).
I would have blindly substituted "word"
in place of "byte" except for
the fact that you subsequently say "12-bit words". I don't know if
"words" is parallel on purpose, as in representing a quantity of two
6-bit word.
I think 'word' was usually used to describe the instruction size (although
some machines also supported 'half-word' instructions), and also the
machine's 'ordinary' length - e.g. for the accumulator(s), the quantum of
data transfer to/from memory, etc. Not necessarily memory addresses, mind -
on the PDP-10, those were 18 bits (i.e. half-word) - although the smallest
thing _named_ by a memory addresses was usually a word.
Noel 
2:08 p.m.
On 1/6/19 11:25 AM, Guy Sotomayor Jr via cctalk wrote:
I think it?s also telling that the IETF uses the term
octet in all of
the specifications to refer to 8-bit sized data. As ?byte? (from
older machines) could be anything and is thus somewhat ambiguous.
It *may* have been the IBM 360 that started the trend of Byte == 8-bits
as the 360?s memory (in IBM?s terms) was byte addressable and the
instructions for accessing them were ?byte? instructions (as opposed
to half-word and word instructions).
Thank you for the clarification.
My take away is that before some nebulous point in time (circa IBM's
360) a "byte" could be a number of different bits, depending on the
computer being discussed. Conversely, after said nebulous point in time
a byte was standardized on 8-bits.
Is that fair and accurate enough? - I'm wanting to validate the patch
before I apply it to my mental model of things. ;-)
--
Grant. . . .
unix || die
2:35 p.m.
On 01/06/2019 02:08 PM, Grant Taylor via cctalk wrote:
On 1/6/19 11:25 AM, Guy Sotomayor Jr via cctalk
wrote:
Yes it was.
Machines around them and in that time frame (mainframe) were 12, 18, 36,
60 bit words.
The big break was mid 1970s with micros first 8008, 8080, 6800 and
bigger machines
like PDP11 (did byte word reads and writes) and TI990.
The emergence of VAX and other 32bit machines made 8bit common as
terminal IO was
starting to standardize.
I think it?s also telling that the IETF uses the
term octet in all of
the specifications to refer to 8-bit sized data.? As ?byte? (from
older machines) could be anything and is thus somewhat ambiguous.
It *may* have been the IBM 360 that started the trend of Byte ==
8-bits as the 360?s memory (in IBM?s terms) was byte addressable and
the instructions for accessing them were ?byte? instructions (as
opposed to half-word and word instructions).
Thank you for the clarification.
My take away is that before some nebulous point in time (circa IBM's
360) a "byte" could be a number of different bits, depending on the
computer being discussed.? Conversely, after said nebulous point in
time a byte was standardized on 8-bits.
Is that fair and accurate enough?? -? I'm wanting to validate the
patch before I apply it to my mental model of things.? ;-
There is no hard before and after as systems like DEC10 and other
persisted for a while.? Also part of it was IO codes for the
EBDIC, Flexowriter, ASr33 (8level vs Baudot), and CRT terminals emerging
with mostly IBM or ANSI.
I am somewhat DEC and personal computer (pre IBM PC) centric on this as
they were he machines I got to see
and work with that were not in rooms with glass and white coated
specialists.
Allison
2:24 p.m.
On 01/06/2019 01:19 PM, Noel Chiappa via cctalk wrote:
As far as
what other systems supported especially the 7094 and GE, that
is already out
of context as the focus was a Russian PDP-8 clone.? Any other machines
are then thread
contamination or worse.
In the early days a byte was the smallest recognized group of bits for
that system
and in some case its 9 bits, 6bits as they were even divisible segments
of the machine
word.? This feature was the bane of programmers as everyone had a
different idea
of what it was and it was poison to portability.
For PDP-8 and friends it was 6 bits and was basically a halfword, also
used as stated for
6bit subset of ASCII (uppercase, TTY codes).? Most of the 8 series had
the bit mapped
instructions (DEC called the microcoded) for doing BSW, byte swap,? swap
the
lower half of the ACC with the upper half.? Very handy for doing
character IO.
The PDP-8 and 12bit relations the instruction word and basic
architecture was 12bit word.
There were no instructions that were a half word in length or other
fragmentations.? The
machine was fairly simple and all the speculated concepts were well
outside the design
of the PDP-5/8 family.?? For all of those the instruction fetch, memory
reads and write
were always words of 12bits.?? I'd expect a Russian PDP-8 clone to be
the same.?? After
all DEC did widely gave out the data books with nearly everything but
schematics.? The
value of copying is software is also copied.? It happened here with the
DCC-112 a
PDP-8e functional clone.
While its possible to use half word ram with reconstruction the hardware
cost is high
(registers to store the pieces) and it would take more to do that than
whole 12bit words.
Any time you look at old machine especially pre-IC registers were costly
and only done
as necessity dictated as a single bit flipflop was likely 4 transistors
(plus diodes and other
components) or more to implement never minding gating.?
Minor history and thread relative drift...?
The only reason people didn't build their own PDP-8 in the early 70s was
CORE.? It was
the one part a early personal computer (meaning personally owned then)?
was difficulty
to duplicate and expensive outright buy.? Trying to make "random" core
planes that
were available work was very difficult due to lack of data, critical
timing, and the
often minimal bench (and costly) test equipment. ? The minimum gear for
seeing
the timing was a Tek-516 and that was $1169(1969$). ? Semiconductor ram was
either a few bits (4x4) or 1101 (three voltage 256x1) at about 8$ in
1972 dollars.? That
made the parts for a 256x12 a weeks pay at that time (pre-8008) and a
4Kx12 with parts
was nearly that of a new truck (2100$)!. ? Compared the basic logic of
the 8e (only
three boards of SSI TTL) core/ram was the show stopper.? About 7 years
later a 8K8
S100 ram was about? (early 1979) 100$, by 1980 64kx8 was 100$.?? Moore's
law was
being felt.
The small beauty of being there...?? FYI back then (1972) a 7400 was
about 25 cents
and 7483 adder was maybe $1.25.? Least that's what I paid.
Allison
From: Grant
Taylor
Is "byte" the correct term for 6-bits?
I thought a "byte" had always
been 8-bits.
I don't claim wide familiary with architectural jargon from the early days,
but the PDP-10 at least (I don't know about other prominent 36-bit machines
such as the IBM 7094/etc, and the GE 635/645) supported 'bytes' of any size,
with 'byte pointers' used in a couple of instructions which could extract and
deposit 'bytes' from a word; the pointers specified the starting bit, and the
width of the 'byte'. These were used for both SIXBIT (an early character
encoding), and ASCII (7-bit bytes, 5 per word, with one bit left over). I would have
blindly substituted "word" in place of "byte" except for
the fact that you subsequently say "12-bit words". I don't know if
"words" is parallel on purpose, as in representing a quantity of two
6-bit word.
I think 'word' was usually used to describe the instruction size (although
some machines also supported 'half-word' instructions), and also the
machine's 'ordinary' length - e.g. for the accumulator(s), the quantum of
data transfer to/from memory, etc. Not necessarily memory addresses, mind -
on the PDP-10, those were 18 bits (i.e. half-word) - although the smallest
thing _named_ by a memory addresses was usually a word.
Noel 
4:54 p.m.
On 1/6/2019 12:24 PM, allison via cctalk wrote:
The small beauty of being there...?? FYI back then
(1972) a 7400 was
about 25 cents
and 7483 adder was maybe $1.25.? Least that's what I paid.
Checks my favorite
supplier.
$1.25 for 7400 and $4.00 for a 7483.
It has gone up in price.
Allison
Ben.
7 Jan
7 Jan
9:51 a.m.
On Sun, Jan 06, 2019 at 02:54:08PM -0700, ben via cctalk wrote:
On 1/6/2019 12:24 PM, allison via cctalk wrote:
Thanks to inflation, $0.25 in 1972 is worth $1.51 now. Likewise, $1.25 has
inflated to $7.54. So they're cheaper in real terms than they used to be.
However, it's still not entirely comparable, as I suspect nobody's making
74-series chips any more so you're buying NOS. A modern equivalent would be a
microcontroller, which start at well under a dollar.
The small beauty of being there...?? FYI back
then (1972) a 7400 was about
25 cents and 7483 adder was maybe $1.25.? Least that's what I paid.
Checks my
favorite supplier.
$1.25 for 7400 and $4.00 for a 7483.
It has gone up in price. 
10:09 a.m.
On Mon, Jan 7, 2019 at 8:51 AM Peter Corlett via cctalk <
cctalk at classiccmp.org> wrote:
Thanks to inflation, $0.25 in 1972 is worth $1.51 now.
Likewise, $1.25 has
inflated to $7.54. So they're cheaper in real terms than they used to be.
However, it's still not entirely comparable, as I suspect nobody's making
74-series chips any more so you're buying NOS. A modern equivalent would
be a
microcontroller, which start at well under a dollar.
Logic chips still have their uses, and are most certainly still being made.
You can still get 74LS parts, in a DIP package even:
https://www.digikey.com/product-detail/en/texas-instruments/SN74LS00N/296-1…
Note: it's an active production part, too.
Kyle
10:20 a.m.
New subject: so far off topic - capatob - saratov2 computer Russsian pdp8?
On 01/07/2019 09:51 AM, Peter Corlett via cctalk wrote:
On Sun, Jan 06, 2019 at 02:54:08PM -0700, ben via
cctalk wrote:
First I wasn't guessing back.? I was building and buying back then. So
that was what I
actually paid in 1972,? I've been at it since RTL hit the streets.?? The
74 series still
made though more likely 74F, AS, or LS variant and of course CMOS 74ACT
(and cmos friends) as I just bought a bunch.? Dip is getting harder to
get but
the various SMT packages are easy.? Prices for 10 or more of a part are
cheap to cheaper from primary suppliers.? The second tier suppliers are
often several times that.
I figure most of what I did back then is years before many here were born.
However I have enough NOS TTL 74LS, 74AS, 74F series to build several
machines.?
I'm still building, current project is a very compact Z80 CP/M system
using CF
for disk. Mine uses all Zilog CMOS for very low power.? Its a variant of
the
Grant Searle Z80 with memory management added to utilize all of the
124k ram and eeprom.? If you want go look there.
Allison
On 1/6/2019 12:24 PM, allison via cctalk wrote:
Thanks to inflation, $0.25 in 1972 is worth $1.51 now.
Likewise, $1.25 has
inflated to $7.54. So they're cheaper in real terms than they used to be.
However, it's still not entirely comparable, as I suspect nobody's making
74-series chips any more so you're buying NOS. A modern equivalent would be a
microcontroller, which start at well under a dollar.
The small beauty of being there...?? FYI back
then (1972) a 7400 was about
25 cents and 7483 adder was maybe $1.25.? Least that's what I paid.
Checks my
favorite supplier.
$1.25 for 7400 and $4.00 for a 7483.
It has gone up in price.
7:25 p.m.
New subject: so far off topic - capatob - saratov2 computer Russsian pdp8?
On 1/7/2019 8:20 AM, allison via cctalk wrote:
snip...
made though more likely 74F, AS, or LS variant and of
course CMOS 74ACT
(and cmos friends) as I just bought a bunch.? Dip is getting harder to
get but
the various SMT packages are easy.? Prices for 10 or more of a part are
cheap to cheaper from primary suppliers.? The second tier suppliers are
often several times that.
I got ebay... The bottom of the heap.
I figure most of what I did back then is years before
many here were born.
However I have enough NOS TTL 74LS, 74AS, 74F series to build several
machines.
I have been playing around with a early 70's TTL computer design
and 74LS181's are too slow by 30 ns. Using a BLACK BOX model for core
memory, I can get a 1.2us memory cycle using a 4.912 MHz raw clock
but I need a few 74Hxx's in there. Proms are 256x4 60 ns and 32x8 50 ns.
Do you have your 74Hxx spares? Eastern Europe still has a few on ebay
with reasonable shipping for 100% American Russian parts.
I'm still building, current project is a very
compact Z80 CP/M system
using CF
for disk. Mine uses all Zilog CMOS for very low power.? Its a variant of
the
Grant Searle Z80 with memory management added to utilize all of the
124k ram and eeprom.? If you want go look there.
What do you use all that memory for?
Allison
The Chinese elves have been busy, My 5V 15 amp $20 power supply arrived
in the mail today. I have power to spare for my BUS and blinking lights.
Ben.
8:51 p.m.
New subject: so far off topic - capatob - saratov2 computer Russsian pdp8?
On 01/07/2019 07:25 PM, ben via cctalk wrote:
CP/M the allocation block store for each drive and deblocking buffers
for performance
can be large plus its easy to hide part of the Bios in banked ram.?
Background processes
are easier when you have lots of ram for that.? Most of the larger aps
like C compilers
and such run better with more than 48K, 56k is easy, and 60k is doable
with the
right memory map.
For EEprom its more than boot, the system is in EEprom (about 8K) and
with 32K
or more things like romdisks and utilities are easily parked there.
I've been building nonstandard CP/M systems since 79.? In all cases he
aps think
it is standard CP/M but the bios and such have been tuned even CP/M Bdos
it self.
Though I often use ZRdos or ZSdos as they are very good.? Not much you
cant do
to it.
Allison
The Chinese elves have been busy, My 5V 15 amp $20 power supply arrived
in the mail today. I have power to spare for my BUS and blinking lights.
So long as you load it at least 10% it will be good.
On 1/7/2019 8:20 AM, allison via cctalk wrote:
snip...
No use for 74H parts though I have a bunch.
the 74LS are slow? you are paying for lower power with speed.? tHe 74181
and 74S181 were far faster.
Proms are small and slow, last time I used them was for the address
decode used on the Northstar* MDS-A controller.
I built the last big machine with ram back 1980 and was in the 1us
instruction
cycle time for single cycle instructions without pipelines.? Core was never
considered.? Trick is throw hardware at it.? Adding adders to the address
calculation rather than reuse the ALU saves a lot of time and wires.?? Not
like it was for manufacture or anything like that.? More of an exercise.
I still want to make a stretched 8, PDP8 ISA with 16 bits and faster.
No good reason save for it wold be fun.
made though more likely 74F, AS, or LS variant
and of course CMOS 74ACT
(and cmos friends) as I just bought a bunch.? Dip is getting harder to
get but
the various SMT packages are easy.? Prices for 10 or more of a part are
cheap to cheaper from primary suppliers.? The second tier suppliers are
often several times that.
I got ebay... The bottom of the heap.
I figure most of what I did back then is years
before many here were
born.
However I have enough NOS TTL 74LS, 74AS, 74F series to build several
machines.
I have been playing around with a early 70's TTL computer design
and 74LS181's are too slow by 30 ns. Using a BLACK BOX model for core
memory, I can get a 1.2us memory cycle using a 4.912 MHz raw clock
but I need a few 74Hxx's in there. Proms are 256x4 60 ns and 32x8 50 ns.
Do you have your 74Hxx spares? Eastern Europe still? has a few on ebay
with reasonable shipping for 100% American Russian parts.
I'm still
building, current project is a very compact Z80 CP/M system
using CF
for disk. Mine uses all Zilog CMOS for very low power.? Its a variant of
the
Grant Searle Z80 with memory management added to utilize all of the
124k ram and eeprom.? If you want go look there.
What do you use all that memory for?
Ben.
9:22 p.m.
New subject: so far off topic - capatob - saratov2 computer Russsian pdp8?
On 01/07/2019 07:51 PM, allison via cctalk wrote:
I still want to make a stretched 8, PDP8 ISA with 16
bits
and faster. No good reason save for it wold be fun.
Umm, I think that is called a
Data General Nova!
Jon
2094
days inactive
2096
days old
11 comments
8 participants
participants (8)
-
abuse＠cabal.org.uk -
allisonportable＠gmail.com -
bfranchuk＠jetnet.ab.ca -
cctalk＠gtaylor.tnetconsulting.net -
elson＠pico-systems.com -
ggs＠shiresoft.com -
jnc＠mercury.lcs.mit.edu -
kylevowen＠gmail.com