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homebrew 8008 project

L

~llama

Member
Joined
Jul 23, 2003
Messages
42
Location
Memphis
Well, my homebrew project (the Neptune) will probably be a very close near-clone of the Mark 8 with one major difference: the processor will be homebrew too; I want to try to build an 8008 out of TTL chips :D i know, i'm crazy...

Anywho... I have the 8008 user's manual and block diagrams, i know how it works, but i have pretty much zero experience with designing TTL circuits (this was intended to be how i learn that)... so i'm calling on you guys with experience with TTL stuff (i hope)...

Are is there anything out there comparable to a schematic for the 8008? I know that Datapoint implemented it in TTL in the 2200, so there have to be schematics out there -somewhere- but... does anyone know where anything like this might exist?
 
TTL chips are basic logic IC's, like registers, flip-flops, etc... so if you assemble enough of them you get a working CPU. the 8008 was originally created for some datapoint terminal, implemented in these logic chips, and intel condensed all the logic onto one chip, and the 8008 was born.

Basically you design the processor and implement the parts of it with chips of less logic integration than a microprocessor.
 
"~llama" wrote:

> TTL chips are basic logic IC's, like registers, flip-flops,
> etc... so if you assemble enough of them you get a
> working CPU. the 8008 was originally created for
> some datapoint terminal, implemented in these logic
> chips, and intel condensed all the logic onto one chip,
> and the 8008 was born.

That seems like quite a trickly thing to do building a
microprocessor, or is it actually easier to go through
the process than to actually describing it?

> Basically you design the processor and implement
> the parts of it with chips of less logic integration than
> a microprocessor.

The only thing I understand, is that it's all microscopic
& supposed to be quite a delicate operation.

Cheers,
CP/M User.
 
hwhall said:
Actually, the Scelbi 8H used the "8008 CPOU on a chip". Some of the original documentation is at http://users.techline.com/cmlove/scelbi/scelbi.htm
Click to expand...

Hmm. . . you're right, of course. Maybe it was the Kenbak-1 I was thinking of. . .

I know there is an early 1970s, pre-Mark-8 machine that is considered by some, at least, to be a PC that was all TTL.

Erik
 
"Erik" wrote:

>> Actually, the Scelbi 8H used the "8008 CPOU on a
>> chip". Some of the original documentation is at
>> http://users.techline.com/cmlove/scelbi/scelbi.htm

> Hmm. . . you're right, of course. Maybe it was the
> Kenbak-1 I was thinking of. . .

> I know there is an early 1970s, pre-Mark-8 machine
> that is considered by some, at least, to be a PC that
> was all TTL.

How about this one:

DATAPOINT 2200 Computer Terminal Corporation (CTC)

according to old-computers.com/museum this machine
came out in 1971 & uses TTL logic which is said to be
equivalent to the 8008. According to this site, the Mark 8
came out in 1974.

Cheers,
CP/M User.
 
The Datapoint was a minicomputer, though. The Kenbak, the Scelbi and the Mark-8 were very early microcomputers.

Erik
 
"Erik" wrote:

> The Datapoint was a minicomputer, though. The Kenbak,
> the Scelbi and the Mark-8 were very early microcomputers.

So this is only a part of the machine then?

ctc_datapoint-2200_1.jpg


Cheers,
CP/M User.
 
I'm not sure if it is or it isn't the whole machine. I am speaking more to the intent of the design.

There's always been a fine line between mini and micro but the basic premise of a micro is "one user" while the basic premise of a mini is "one workgroup."

From what I understand of the Datapoint products, they were workgroup type machines.

I could be wrong. It's happened before at least once in this thread alone! :)

Erik
 
"Erik" Wrote:

> I'm not sure if it is or it isn't the whole machine. I am speaking
> more to the intent of the design.

> There's always been a fine line between mini and micro but the
> basic premise of a micro is "one user" while the basic premise of a
> mini is "one workgroup."

> From what I understand of the Datapoint products, they were workgroup
> type machines.

> I could be wrong. It's happened before at least once in this thread
> alone! :)

Oh okay, I can only go by what old-computers.com has on their website &
unfortunately it doesn't speak in terms of what the user base is. It
does say in their website that the company came up with a LAN, but I'm
unsure if they made it for this machine or for others. Also even
though the Datapoint 2200 used TTL logic for the CPU, it was
responcible for the success of the 8008. But apart from that, I don't
know much more, or if it is a type of Minicomputer (since
old-computers.com is looking at machines which pre-date the
Microcomputer).

Cheers,
CP/M User.
 
Speaking of oldcomputers.com, I really do like that site.

When I first started with www.vintage-computer.com I considered implementing a database driven site with user-contributed machine information. In the end I decided that I didn't really have the time to implement that with all of the other things I had going in life.

It's still in the back of my mind, though, and someday I hope to get enough free time to take a shot at it.

Erik
 
"Erik" wrote:

> Speaking of oldcomputers.com, I really do like that site.

It's fine when they get their information right.

But when they fail to mention about the TI 99/4 & that it
was a seperate system from the TI 99/4A they look
stupid, which doesn't help from the fact that they're been
told & it still remains uncorrected!

Instead they insist that the TI 99/4A came out in 1979
which is a mistake & that the TI 99/4A is a 16bit computer
& the TI 99/4 was an 8bit!

> When I first started with www.vintage-computer.com I
> considered implementing a database driven site with
> user-contributed machine information. In the end I
> decided that I didn't really have the time to implement
> that with all of the other things I had going in life.

That's okay, I see someone has tried to correct the TI99/4A
page by adding comment to the TI 99/4, but since the info
is inacurate in the Technical Info section, they should be
made to correct that, since people like myself & perhaps
others have made mistakes based on their mistakes!

> It's still in the back of my mind, though, and someday
> I hope to get enough free time to take a shot at it.

Perhaps just make sure that's correct before posting it
on your website. Due to the mistakes done to that
computer the TI 99/4x series, they should really have
2 seperate pages which talk about these 2 systems. As
it is, they have to do a bit of work to get it right & since
I've told them & nothing has been done, then I feel they
are too lazy to get off their behinds & fix it! :-(

But apart from that, their okay.

Cheers,
CP/M User.
 
CP/M User said:
"Erik" wrote:

> Speaking of oldcomputers.com, I really do like that site.


Instead they insist that the TI 99/4A came out in 1979
which is a mistake & that the TI 99/4A is a 16bit computer
& the TI 99/4 was an 8bit!


Cheers,
CP/M User.
Click to expand...

Really? I didn't know that the 99/4 was an 8-bitter. Do you know what processor it used? Was it still the same 9900whatever (partially disabled) that they used in the 99/4A?

--T
 
Terry Yager said:
Really? I didn't know that the 99/4 was an 8-bitter. Do you know what processor it used? Was it still the same 9900whatever (partially disabled) that they used in the 99/4A?
Click to expand...

I always thought that the 99/4 and 99/4a differed mainly in the keyboard.

I've never used a 99/4, though. Just the "a" model.

Erik
 
"Terry Yager" wrote:

>>> Speaking of oldcomputers.com, I really do like that site.


>> Instead they insist that the TI 99/4A came out in 1979
>> which is a mistake & that the TI 99/4A is a 16bit computer
>> & the TI 99/4 was an 8bit!

> Really? I didn't know that the 99/4 was an 8-bitter. Do
> you know what processor it used? Was it still the same
> 9900whatever (partially disabled) that they used in the
> 99/4A?

Yes it was the same processor as a matter of fact. Someone
told me that the 99/4 was 8bit, most of the other technical
specs are also the same, except for the year it came out.

Since TI created their own CPU, I'd imagine that the
modified this for the 99/4A.

Cheers,
CP/M User.
 
Erik said:
Terry Yager said:
Really? I didn't know that the 99/4 was an 8-bitter. Do you know what processor it used? Was it still the same 9900whatever (partially disabled) that they used in the 99/4A?
Click to expand...

I always thought that the 99/4 and 99/4a differed mainly in the keyboard.

I've never used a 99/4, though. Just the "a" model.

Erik
Click to expand...

Both the TI-99/4 and the TI-99/4A use the TMS-9900 microprocessor, (not partially disabled at all, the same chip used in their business systems) which is a 16-bit CPU in the same way that an 8088 is 16-bit.

The keyboard is the main physical difference, the /4 had a calculator-type keyboard which was disliked immensely. The reason for the A in TI-99/4A is that the Video Display Processor was changed from the TMS-9918 to the TMS-9918A, which is a much more significant difference.

With a few exceptions, the two computers run the same modules.
 
"barryp" wrote:

>>> Really? I didn't know that the 99/4 was an 8-bitter.
>>> Do you know what processor it used? Was it still the
>>> same 9900whatever (partially disabled) that they
>>> used in the 99/4A?

>> I always thought that the 99/4 and 99/4a differed
>> mainly in the keyboard.

>> I've never used a 99/4, though. Just the "a" model.


> Both the TI-99/4 and the TI-99/4A use the TMS-9900
> microprocessor, (not partially disabled at all, the
> same chip used in their business systems) which is a
> 16-bit CPU in the same way that an 8088 is 16-bit.

> The keyboard is the main physical difference, the /4
> had a calculator-type keyboard which was disliked
> immensely. The reason for the A in TI-99/4A is that
> the Video Display Processor was changed from the
> TMS-9918 to the TMS-9918A, which is a much more
> significant difference.

> With a few exceptions, the two computers run the
> same modules.

The 99/4A would have came out later than the 99/4
though wouldn't it?

Okay, so I mixed up the CPU as being the difference,
though I did know it was some hardware difference
about those machines. Unfortunately, the books I
have don't go into this very well, well since they were
mean't for the real hardware 'buffs.

Cheers,
CP/M User.
 
CP/M User said:
The 99/4A would have came out later than the 99/4
though wouldn't it?
Click to expand...

Yes, of course.

CP/M User said:
Okay, so I mixed up the CPU as being the difference,
though I did know it was some hardware difference
about those machines. Unfortunately, the books I
have don't go into this very well, well since they were
mean't for the real hardware 'buffs.
Click to expand...

There are other minor differences too, not worth mentioning.
 
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