restarting AltairPC project in near future because of this

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Postby vbriel » Jun Wed 18, 2008 9:45 pm

Well, while waiting patiently for the boards to arrive late next week I decided to check out Protocase. This company will custom make a case for you for PC to any specs desired. Yes, if I send them a drawing of an Altair they could make a case like it. I just read Tom's Hardware review and it was stunning. They made a custom one of a kind round case with custom cut out logo for like $1400. OUCH! Well, I'm going to see if they can do something a little cheaper, like $300. I want factory done case so that I'm not hacking cases together in my garage. Plus, the quality would be outstanding.

I'll see what they can do that looks good/close to an Altair and is the right price.

Here's there website for easy access:

http://www.protocase.com/index.php

What do you think?

Vince
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Postby ggnagy » Jun Mon 23, 2008 3:40 pm

vbriel wrote:Well, what makes S100 compatibility? You just need to run the signals to the appropriate connections on the S100 bus, right?

So, an adapter is possible (and if there is enough interest I'll make one) but my design isn't set on being a full blown system. For example, when addressing the 6850 IO address, as a result of chip reduction it will not only work at 20 and 21 octal but any of the first 127 decimal addresses and the front panel sense switches will be active on 128-255 decimal IO address. So, there really isn't room for expansion with the IO. I may change this if there is enough demand for more ports, S100, etc.

Buffering of the address and data bus; Not done, not needed for 1 or 2 chips attached. For expansion, full bus buffering would be needed.

So, some changes will probably happen before I make more but I need to meet the initial final goal to load BASIC. I'm going to try them all but shoot for extended BASIC.



The AltairPC just seems to be a step in a different direction than the Replica I and the Kim. My thoughts were that with a standard bus, homebrewers would have a chance to develop expansion cards for the system, much in the same way a sub-industry grew around creating expansion cards for the Altair and follow on S-100 machines.

If you are interested in either a singleboard AltairSBC or the AltairPC, give feedback, opinions, etc. Even if I shoot the idea down, be heard and be part of the design process. The prototype I'm making isn't a final board and changes can be made.


Maybe I am mis-remembering, but was there an earlier generation of this project, where the front panel was an interface to an Altair emulator running on the encased PC? I am just once voice, but I would think the Altair SBC would win out over the Altair PC, as I do not see the needed overhead of having yet another computer/case around the house. One alternative thought is the wall mounted setup Spare Time Gizmos had with their SBC6120/FP6120 pdp 8 box. YMMV
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Postby vbriel » Jun Mon 23, 2008 5:30 pm

The original concept of the AltairPC was a simple microcontroller that could emulate the front panel of the Altair and 8080 but it wasn't a full bus system. The IMSAI is more like what you are describing. It is a fully functional front panel with an EZ80 u-controller as the CPU connected to a S100 bus.

Yes, the AltairPC is a major step in a different direction than the replica 1 and the Micro-KIM. Those projects were aimed at a reproduction of a singleboard computer with some changes to either make them smaller, or fewer components. The AltairPC was a concept on how generic PC's had become and what kind of computer case would a computer collector such as myself like to see.

Since the Altair SBC uses toggle switches the SBC needs to sit upright and in some type of frame like Spare Time's PDP-8. I have a front dress panel prototype sitting here with no frame and it is awesome. The 50 pin header is perfect to add a ribbon cable to some type of bus, either S100 or a homebrew.

The nice thing about this project is that it is going in 3 different directions:

A single board computer expandable and hobby experiment ready
A PC case that functions like an Altair

The third direction is still in the planning stages but will be really cool too. All 3 will be expansion compatible so that anybody that designs hardware for one, it should work with the other 2.

I'm going to try and get a photo of the dress panel up shortly.

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Postby vbriel » Jun Wed 25, 2008 1:48 pm

Well, still waiting for boards, they should ship tomorrow if the board house is on time. Making changes to the expansion header so that you can enable or disable the onboard RAM remotely. I've also added a Data bus buffer to help if somebody is going to attach the Front panel to a S100 bus system or fully expand the system.

Image

This is the current 50 pin header setup. It will be on the left edge in a right angle .100" IDC header so the pins flow to the back behind the panel.

Does this appear to have all the pins needed for you guys to hack with? I don't want to add any unnecessary signals but that is all of the CPU signals, the Data bus D0-D7 is buffered, RAMEN is a signal that helps enable RAM when MREQ is active low. 32KEN needs to be attached to MREQ to enable the onboard 32K. There is a jumper onboard to disable it so you can control it remotely.

RAMEN is probably not needed as an expansion signal so I can remove it if there is another signal more important.

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Postby CodeJockey » Jun Fri 27, 2008 8:44 am

Is the IO fully decoded? If not, a signal to enable/disable the on board IO might also be useful.
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Postby vbriel » Jun Fri 27, 2008 1:52 pm

Well, there are open ports available but I'll look into an IOEN line or something. I'll see what I can do. Anything else? My boards didn't arrive today so no building prototype and taking photo's this weekend :cry:

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Postby CodeJockey » Jun Fri 27, 2008 3:06 pm

As long as there are ports available that is cool. Somehow I had gotten the impression that all of the IO ports were taken due to incomplete decoding.

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Postby vbriel » Jun Fri 27, 2008 4:08 pm

Right now, I have it set up so anything that uses A7 in a port goes to the front panel. This was for the easiest way to keep chip count low.

The lower addresses available are anything that A4 isn't high, so:

bit 6 5 4 3 2 1 0
X X 0 X X X X

Anytime bit 4 of the address bus is a zero, the 6850 is not active and that port is available. Remember, if bit 7 (A7) is active, it is the front panel port).

This means that ports 00-0F (000-017 Octal) are available for use. 10-1F (020-037) are used and repeating for the serial 1SIO port. 20-2F are available (0x40-057 Octal). and it repeats from there.

Funny, I never use Octal until now. Since the Altair code gets programmed in Octal, I have to include the Octal addresses.

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Postby vbriel » Jun Sat 28, 2008 6:26 am

The prototypes have shipped from the boardhouse and will arrive on Tuesday. So, I'll build one Tuesday night and start testing.

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Postby vbriel » Jul Sat 05, 2008 9:11 pm

Ok, I've got a prototype built and working and I'm trying to get one of these loaders to work and load basic but I'm not having any luck.

Here's what I know works.

The serial port can send and receive data. I've loaded that little test program that echo's what you type back out. It works at 9600 perfect.
Port 255 for the front panel works. I wrote a little program that reads the front panel switches and outputs the data to the serial port.
I can read/write to/from memory with no errors. I wrote a small program that just stores a increasing value to memory and the memory locations increase. All tests worked great.

What I'd like is a small loader program that is around $7000 in memory so it is well out of the way and just simply dumps basic into memory. I have a copy of BASIC that if just dumped straight in should work (works on Rich Cini's Altair32 emulator).

I tried writing a loader but it skips every other byte coming in. It's not coming too fast because I've even tried adding a character delay of 500ms and that didn't change anything.

Can somebody write a small dump program that will read data from port 20/21 and dump it starting at 0000 and increase until the user stops the program?

The Z80 isn't my most used cpu, I use 6502 and RISC style assembler more.

Thanks for any help. Everything else is going great and this is the final stage I want working before I can take this project to production!

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Postby vbriel » Jul Sun 06, 2008 3:17 pm

Getting closer. Using the Altair loader I can get the 8K to come up to MEMORY SIZE? and then if I hit enter it locks. If I enter a value it goes on to TERMINAL WIDTH? Once again, a value seems to work. I then get the SIN, COS, etc, and when I enter Y, once again it locks. Slowly it's coming around.

BASIC must load.

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Postby vbriel » Jul Sun 06, 2008 10:08 pm

Well, after several attempts I finally got BASIC loaded. This is a pain but I think it will get easier.

Image

This is extended BASIC loaded and working. I'm trying it again and will try the other versions as well.

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Postby vbriel » Jul Wed 09, 2008 6:43 am

Ok, just an update for people. The only working version so far is extended BASIC. The 4K and the 8K haven't loaded properly to a running prompt yet.

EXTENDED BASIC loads but there are small issues. Variables don't show any value.

For example, if I do LET A=5:PRINT A it will print a zero. If I say PRINT A+5 it will print a 5. Minor but important. Variable storage isn't working properly.

Also if I have a line that says 10 GOTO 5 if will list as saying 10 GOTO 0

The line works correctly but the variable for the goto statement is showing incorrectly. I need to find where variables are being stored and why they aren't working correctly. Appears to be a memory issue at this point.

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Postby vbriel » Jul Tue 15, 2008 11:35 pm

Still debugging BASIC, no answers yet. 4K and 8K ask the beginning questions, then it linefeeds and stops short of announcing the BASIC version. I've tried several versions of this with the same result.

The extended 4.0 and 5.0 versions load but with the above error conditsions. The conditions may be related somehow.

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Postby CodeJockey » Jul Wed 16, 2008 11:05 am

With the memory map of your SBC being as simple as it is, it may be beneficial to hack together a quick and dirty PC emulator for it, and then trace the basic assembly code as it starts up. That may help you narrow the problem down quite a bit.
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