Altair 8800c S/N 13219 Build Thread

[Sirius Arcturus]

Tom if you’d want to let me test that prototype board in my 8800c I’d be more than happy :)

Also I’ve visited your site now — so much to see there! I’ll get back to you about it after I’ve consumed more. But I can already recommend http://www.virtualaltair.com to anyone who hasn’t seen it yet.

And to all, I’ve just completed this 88-VI(RTC) board from one of the bare reproduction boards available from JM Precision Components in the UK. Finding all the parts was like going on a journey, but not too bad at all and kind of fun.
I’m hoping to get Timesharing BASIC going with it.

88-VI(RTC) Front

88-VI(RTC) Back

[Wayne Parham]

Very nice!

[Sirius Arcturus]

Thanks, Wayne!

And I can now report I did in fact get Timesharing BASIC 1.1 running successfully with some input from Mike. He pointed out I needed to change the RTC division jumper from “AD” to “CD” to divide the 10 kHz signal from CF to provide a 100 Hz clock which works. This allows me to run TS BASIC on the 8800x which is very enjoyable.

Additionally, as I am using the 88-2SIOJP with default address settings, I needed to set terminal 1 to 1 device at address 16, and terminal 2 to 1 device at address 18. Thanks, Mike, for your help.

Since then, I’ve now completed building up one of JM Precision’s reproduction 88-16MCS memory boards. This was an ultra fun build and I ended up with only one bad 4200 chip. The memory test at 046 allowed me to recognize it was in bank “C”, and then I swapped out chips in “C” until I found it. I also could have examined the bit patterns of the failing data and identified the exact chip in “C”, but I did not do that.

I am beginning now a build of a second one of these.

Here are photos of the completed one.

Sirius

88-16MCS front

88-16MCS reverse

[Wayne Parham]

Very cool. I love the new PCB versions of original boards. Just very cool.

I built a couple of Jerry's 64K battery-backup "core" boards. They are a simple design 'cause they use newer chips. But they aren't Altair-reproduction boards like yours.

And I'm using the RAM on the FDC+ board, so my "battery core" boards aren't being used. I keep thinkin' I'll disable the FDC+ memory and put in the core boards, but I haven't yet.

I might have to get boards like yours so I can make a closer-to-1970s Altair, maybe put it in my "red" system.

[Sirius Arcturus]

Wayne,

I know which 64K board you mean. Jerry makes very nice boards. The two different boards of his I’ve built were a joy to work on.

I agree, it’s been so nice to have the FDC+ memory. It took some “explaining” for my wife to finally (sort of) get it why I’d want to build (and pay for the parts for) an old school board — which only holds 1/4 the max RAM — whenever I already have the max RAM in a single chip which will never, ever, ever fail a memory test. Lol

Truth is, I’ve begun building a second one now. I have enough 4200 chips for a second one and a third one, depending on how many are actually good.

I did the same thing you mentioned and that is I set 16K board to be the first 16k, and set the FDC+ to start at 4000H. Hoping to be able to switch it to 8000H soon :)

Oh also I’ve been meaning to mention I’m using the same 5.25” FD enclosure you are using two of. After seeing yours I looked and found one on eBay. Nice and easy to use with power supply and fan already built in.

[Sirius Arcturus]

Here is a current operating photo.

8800c operating

[virtualaltair]

What software are you using for a memory test of the 88-16MCS? What do you estimate for the parts cost of a single 16K memory board? I think an original 16K board would be $300 on eBay. That makes the FDC+ 64K a bargain.

[Wayne Parham]

Your system looks awesome! Really nice job!

[toml_12953]

Thanks, Wayne!

And I can now report I did in fact get Timesharing BASIC 1.1 running successfully with some input from Mike. He pointed out I needed to change the RTC division jumper from “AD” to “CD” to divide the 10 kHz signal from CF to provide a 100 Hz clock which works. This allows me to run TS BASIC on the 8800x which is very enjoyable.

You really want Timesharing BASIC 2.0. With version 1.1, you can't open files, among its other limitations.
It's available in the same place you can get 1.1.

[Sirius Arcturus]

What software are you using for a memory test of the 88-16MCS? What do you estimate for the parts cost of a single 16K memory board? I think an original 16K board would be $300 on eBay. That makes the FDC+ 64K a bargain.

Hi Tom,

I used the memory test located at 046Q on the 8800c. There is firmware on the front panel microcontroller that has a few small programs you can deposit with setting an address and depressing AUX Left. The memory test is one of them. This AUX Left behavior is of course a modern addition and as such can be enabled or disabled as desired.

I also have AMON in PROM which has a memory test too. It runs quite a few passes and then returns to the AMON prompt, whereas the (version of the) one I have on the front panel runs passes continuously until you reset the machine.

Both let you choose start end endpoints.

The parts and board weren’t too much, and I had many of the parts already. The style of sockets I chose are kind of high, but the real expense was the 4200 chips. I need a minimum of 5 more and I can fully populate a third board! If anyone has 5 or so to sell please PM me :)

I just finished board number two and miraculously, this one ran the first time with zero errors! No bad RAM at all!

88-16MCS repro build #2 (front)

88-16MCS repro build #2 (reverse)

4200 RAM top