On 5/26/2020 9:50 AM, Liam Proven via cctalk wrote:
On Mon, 25 May 2020 at 20:53, Jim Brain via cctalk
<cctalk@classiccmp.org> wrote:
Too late to fix silicon, the 6522 issue surfaced.
What 6522 issue?
TO help save a few bits in everyone's mailbox, I will link to some docs:
http://forum.6502.org/viewtopic.php?f=4&t=1514
The forum post gives some commentary on the bugs.
http://archive.6502.org/datasheets/synertek_sy6522.pdf
However, the TLDR version is that there are bugs in the shift register
implementation that cause too many clock pulses to be sent (mode 010)
and missing IRQ after 8 clock pulses (mode 011/111). Page 8 of the PDF
gives more detail (Section 5.1).
This is way more depth about a machine I never owned than I personally
ever knew, I have to admit...
I am sure all the home computers have these interesting stories, though
most of the world only knows about variations on the 5150 design and the
Mac.
Still, that degree of backwards-compatibility helps adoption of a new
model. ZX Spectrum owners could keep their ZX Printer from their ZX81,
for instance, and BASIC programs would still run. (Although I think
you had to re-enter them all -- not sure about tape storage
compatibility.)
I agree and can't fault the logic. We who bought a VIC-20 and then
upgraded and were penniless kids were ecstatic.
Done, except Japan
didn't see any need for it, so they deleted it. Argh!
But I thought the Japanese model didn't sell?
I may have miscommunicated. CBM did their design work in PA, but final
layout and such was done at the Japan office. And, they also tended to
use the Japanese market as a test for US and Europe intros, to iron out
issues. Thus, the VIC-20 final layout was done at the Japan office, and
it was introduced there first (as the VIC-1001).
When designing the C64, the PA design team snuck in a new trace from the
6526 shift register (and bridged one of the IEC lines in place at the
6526 CIA over to the shift register CLK line (most likely the unused SRQ
line on the IEC connector) and then sent the designs to Japan for final
layout.
My theory is that the PA design team didn't dare talk about the extra
traces with leadership, for fear of retribution. I am sure managers
would have been concerned about possible compatibility issues of adding
a trace and demanded it be removed. Jack may have yelled (he was
legendary for that) at the engineer for "adding no value". Or, the
management team might have been actually concerned about the issue,
raised it to Jack, and demanded they fix it but not add the trace. I
think the engineer thought this was a way to add this in for the future,
but not delay the current project and hit show and intro dates. But,
that's my theory.
The Japanese team, not having any knowledge about this "secret" plan to
fix slow IEC speeds, simply optimized the extra traces our of the
design, and since it was final layout, there was no recourse.
To your point, the C116 intro in Japan did indeed bomb.
I must admit, even in 1983 or something, that seemed extravagant to
me. I know that the Apple LaserWriter was a more powerful computer
than the Mac that drove it, but there were sound engineering reasons
for that -- but most 8-bit machines' standard floppy drives didn't
have CPUs, so why did the Commodore ones need them?
Well, I do think Peddle had a great idea. Most drives of the day were
tightly coupled to the machine, which was low cost, but tightly coupled
the hardware. He was familiar with the HP Interface Bus (HPIB), which
is IEEE-488, and the value it created (lots of peripherals, lots of
interconnectedness, etc.). I think he championed the PET have that as
opposed to a direct drive connection. Though IEEE-488 gave way to IEC,
it and related peripheral connects (the Atari SIO bus) actually were a
great design choice, as it makes it that much easier today to interface
contemporary peripheral options to these old machines. While some
systems have to emulate an actual floppy format (80kB or 160kB or
something) when trying to move from spinning disk to SD cards and such,
one can hang a huge FAT32 formatted SD card off the CBM serial bus and
the computer doesn't hardly even know. Most apps just merrily go along.
But, 2 CPUs? That was overkill, in most folks opinions.
Well, for all that it didn't appeal to me, I think it was a decent
design and it sold well.
Can't argue that. Some of us were so desperate for color computing, and
it quickly fell to a reasonable price.
I guess your point is that you don't agree with Jack's priorities. The
VIC was a rush job, costs had to be low. BASIC v2 just fit in an 8kB
ROM, and KERNAL fit in another 8kB. 8kB ROM was easy to make in house.
Notice they used 2 ROMs instead of 1 16kB one. It was all about low NRE
costs, using stuff off the shelf. Putting a third 8kB ROM in there for
better BASIC was just an unneeded IC, plus someone would need to write
the A/V code (CBM did not have a A/V capable BASIC at that time).
But CBM didn't write it in the first place, did they? It's MS BASIC.
MS wrote it, and CBM modified it as needed. BASIC 4.0 I think was wholly
modified from v2 by CBM. Something changed at some point, because none
of the CBM BASIC up to v7 in the C128 had a MS copyright, but v7 (all
changes done by CBM internally) did have the copyright. Not sure if MS
threatened, it was some concession given in licensing a BASIC for Amiga
(I forget it AMigaBASIC was MS-based...), etc.
In the Spectrum, there's no split between OS and BASIC -- they're the
same chunk of code, and it all fits in 16 KB leaving 48 KB of memory
map free for RAM. The initial models of Spectrum (16KB & 48KB) had no
bank switching support at all, AFAIK.
Now, this is a good question. I've seen MS BASIC v2 and VIC and 64
KERNAL (same except for some fixups to fit the 64) and they take up all
of that 16kB. Maybe Z80 code is more compact, or maybe Sinclair was
just better at stuffing code into ROMs. Not sure. But, it is obvious
the Speccy packed more into 16kB than Commodore.
Anyway, back to 6502 machines: the BBC Micro split the OS (MOS) and
BASIC (BBC BASIC) into different ROMs, just as the Commie 64 did.
However, Acorn's ROMs were 16 KB each not 8 KB each. That meant that
with both MOS and BBC BASIC paged in, the base model BBC Micro had
only 32 KB of memory map left for RAM, and that really wasn't enough.
Its highest-res graphics mode took ±20 KB of RAM, leaving a paltry
11KB for programs.
But I guess all this is unknown and irrelevant in the USA, where Acorn
barely sold at all and Sinclair did poorly.
I think the Sinclair options just were not marketed well in US. I
remember considering the ZX81, but really wanted color. I don't
remember seeing the 2068 back in the day. I also don't remember seeing
the Micro, and what was the cost of it in 1984, for example? In '82, the
VIC was 332USD, and in 1984, the 64 was $149. I doubt the other models
could hit those prices. Schools here got the Apple IIs (Apple had some
education program), but lots of us went the cheap route.
Given that the functionality of the Commodore OS and BASIC seemed so
feeble compared to that of the Beeb, I remain surprised to this day
that CBM couldn't squeeze all that into 16KB.
I heartily agree with you there.
Also fair. It's all most British schoolkids wanted, yes.
I collected games like some kids collected stamps: it was fun to have
a good collection, swap and trade, to have the latest or rarities --
but you don't actually _use_ the stamps in your collection, do you? I
didn't actually _play_ all the games. Most I loaded once, had a look
and then never opened again.
We are exactly alike in that. I have boxes of games I collected from
back in the day and I don't think I even loaded some of them up one
time. So much youthful effort squandered on such a useless task :-)
I can appreciate your advocacy of BASIC. I cannot agree with it, and I
liked BASIC (on many machines) growing up. Once I entered software
development as a vocation, I found BASIC had set up bad habits that it
took years to unwind. I still have a fondness for the language, but I
don't think it was all that educational. It was brute force, overly
verbose at times, hard to follow in programs of anything above trivial
sizes, etc. But, it must have it's sheering section, and so I defer to you.
I do not know what a "sheering section" means.
Typo: "cheering". :-)
BASIC made learning programming easy. The result was a whole
generation of kids in the 1980s learned to program and started tech
companies, and many became wealthy or changed whole national
economies.
I will absolutely agree with this. BASIC was the gateway drug. Perhaps
I quibble because easy and good may not be equivalent. Maybe there is a
mutual exclusivity at play. BASIC was easy to learn (kudos to the
designers) and powerful, no argument there. But, I think it scaled badly
and created bad habits (global vars, spaghetti code, etc.) and it put me
a bit behind when I needed to turn my enjoyment of programming into a
vocation. But, if you just wanted to whip up a solution to your
specific problem, and you were not trying to be a professional
programmer, BASIC was awesome (I still use it when I test hardware
designs, since it's so much easier than sitting down to write a machine
language test app.). But, when the adult drops by the introduction to
programming class, you just don't know what category that person is in.
Still, I will agree that it made programming fun, and none of the bad
habits it fostered were all that difficult to unlearn.
Yet you or your family paid in real terms between 4× to 8× as much and
you didn't mind that it had some very serious drawbacks which you
discuss in great detail?
That's astonishing to me.
Well, to be fair to my 10 year old self, living in a rural community, I
probably didn't do very good research. I *wanted* an Atari 2600 (yes,
it's ironic, since I don't play games and really never did), but
everyone had one, and peer pressure is strong. My father, who was a
farmer and mechanic, put his foot down and vetoed the idea, stating that
for that kind of money, the device should do more than play games (I
think the 2600 was $199 or something, maybe was a bit more, memory is
fuzzy). But we lived in the country, so we did our shopping via the
Sears/JC Penny/Montgomery Ward paper catalogs, and all of the units
offered were just as unapproachable as your comments state about the
options in your youth, save the VIC-20. Thus, in comparison, it was
awesome, even though it had issues. I don't remember seeing the
Sinclair or the BBC in those catalogs, and that was probably the extent
of my research.
If I or my parents were spending this very significant sum, perhaps a
month's income for the whole family, then I want something as rounded,
as balanced, as capable in every aspect as can possibly be done for
the price.
My family didn't really care at the time. Maybe in Europe folks took
computers more seriously earlier, but my family saw it as just another
toy the boy wanted. And, it was all my savings I had accumulated. Of
course, I now know we were (and are) privileged concerning income in the
US (and I think my family would be considered lower middle class at the
time), but I didn't know that then. Unlike with food, there was no
"Jim, there are less fortunate children in other countries who cannot
afford this kind of computer, so you better pay a lot of attention to
selecting a valuable option" discussions. I had the cash, I bought the
machine, I enjoyed it.
Yet you say "yeah, well, the BASIC was crappy and the disk drives were
kinda crappy but I didn't care."
This is really quite profoundly shocking to me.
Well, I didn't know they were at first. Initially, I played games on
the VIC, and then tired of it and put it away. A year later, the school
had some, so I dug it out and really started coding on it. We were not
in a large metropolis, and computers were so new around here, no one was
comparing. Later, when things become more well known, we were all
trading games, BASIC was never mentioned, and C64 games used the disk
drive CPU to enable fast disk access, so the slow drive issue just
magically disappeared. I read magazine articles about better BASIC
options and A/V commands in other units, and I think I did lament that,
but I'd made my investment, and the eco-system around here was Atari and
Commodore.
If you mean putting the Z80 in there? Bil agrees with you. He hated the
entire idea, and the engineering effort he expended to do it. But, when
Marketing has promised it, evidently at Commodore, you made it happen.
Hats off the engineers at CSG/MOS/CBM.
Again, I guess we are looking at this in very different ways.
For you, these seem to be small, unimportant issues. For me, at the
time, given the amount of money involved, they would be deal-breakers.
I'd ask for more clarity here. I do think compatibility with 2 obscure
carts was overblown, and maybe you think that was super important. But
maybe you mean the choice of putting the Z80 in there. I can't believe
CBM let him do it, since that piece was so expensive, compared to MOS
parts. But, it happened. Still, I' m not sure your context here.
Jim
