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Search: Posts Made By: Geoff Harrison
Forum: Kenbak-1 04-29-2010, 09:57 PM
Replies: 4
Views: 10,207
Posted By Geoff Harrison
I wonder if a Kenbak renovated by John himself...

I wonder if a Kenbak renovated by John himself would attract higher bids than a pristine one. I might be willing to pay a little more, but I guess that's a moot point since it will probably go for...
Forum: Kenbak-1 04-29-2010, 09:04 PM
Replies: 4
Views: 10,207
Posted By Geoff Harrison
Well, it's actually his daughter who's selling...

Well, it's actually his daughter who's selling it, and I think she's likely to get more bids if she shows more detailed pictures. The picture of John with the machine is good, but interior and...
Forum: Kenbak-1 04-29-2010, 06:57 PM
Replies: 4
Views: 10,207
Posted By Geoff Harrison
Original Kenbak on eBay

Auction id 320522921808

I've asked the seller to post some detailed pictures of the actual machine.

Geoff.
Forum: Altair 8800 09-03-2009, 05:37 PM
Replies: 2
Views: 2,878
Posted By Geoff Harrison
Yes, you're right. A real 8800 will step one...

Yes, you're right. A real 8800 will step one full instruction at a time whereas Rich's emulator steps one byte at a time. There are a few differences (bugs?) in the emulator, but that doesn't...
Forum: Troubleshooting 08-20-2009, 01:50 AM
Replies: 4
Views: 4,683
Posted By Geoff Harrison
Yep, mine is the same. Although, since it starts...

Yep, mine is the same. Although, since it starts up in an unknown state, once in about 20 or so restarts it comes up looking like it's ready to go, but I just automatically hit stop/reset to be...
Forum: Troubleshooting 08-19-2009, 08:59 PM
Replies: 4
Views: 4,683
Posted By Geoff Harrison
The blinkenlights can be pretty subtle on an...

The blinkenlights can be pretty subtle on an 8800, and different memory boards can modify the effect. For example, MITS' 4k board tends to hold all the data lights on when a program is running. ...
Forum: Altair 8800 07-29-2009, 06:38 PM
Replies: 12
Views: 9,733
Posted By Geoff Harrison
If you're getting this far, I don't think you...

If you're getting this far, I don't think you have a communication problem. What you show above is exactly what I get with 4k BASIC with 8N1 parameters. When you set it to 7 bits, do you also set...
Forum: Altair 8800 07-29-2009, 03:14 PM
Replies: 12
Views: 9,733
Posted By Geoff Harrison
Yes, I brought out only the Tx & Rx lines and...

Yes, I brought out only the Tx & Rx lines and left RTS, CTS, & DCD disconnected. To keep the 6850 happy I tied pins 23 & 24 to ground.

http://www.solivant.com/misc_images/2sio_jumpers.jpg


...
Forum: Altair 8800 07-29-2009, 02:41 PM
Replies: 7
Views: 2,798
Posted By Geoff Harrison
I changed it just to be sure, but that's not it. ...

I changed it just to be sure, but that's not it. The problem is that the incoming data stream, after being converted from current loop to TTL voltage swings is not clean enough to drive the 7404...
Forum: Altair 8800 07-29-2009, 01:30 AM
Replies: 12
Views: 9,733
Posted By Geoff Harrison
Oh, also, don't forget to make sure you do the...

Oh, also, don't forget to make sure you do the uploads in binary mode.
It seems like I make that mistake almost Every D**mn Time!!!:rolleyes:
Forum: Altair 8800 07-29-2009, 01:26 AM
Replies: 12
Views: 9,733
Posted By Geoff Harrison
Hi Marty I have posted an image of my 2sio...

Hi Marty

I have posted an image of my 2sio board here (http://www.solivant.com/misc_images/2sio.jpg), it should be big enough to make out the chip markings. It's populated only for RS232, I...
Forum: Altair 8800 07-29-2009, 12:19 AM
Replies: 7
Views: 2,798
Posted By Geoff Harrison
Well, with the diodes installed as per the...

Well, with the diodes installed as per the silkscreen, no input signals were getting through to the UART. After I rotated them, the input was getting through,

but...

the pulses arriving at the...
Forum: Altair 8800 07-28-2009, 09:13 PM
Replies: 7
Views: 2,798
Posted By Geoff Harrison
2SIO silkscreen error

If you're building one of Grant's 2SIO boards, be aware that the silkscreen is incorrect for D3, D6, D9, D12, D15 & D18. The cathode should be up toward the Molex connectors, instead of down as...
Forum: Altair 8800 07-16-2009, 04:10 PM
Replies: 20
Views: 6,312
Posted By Geoff Harrison
My address was on the box and I also just sent...

My address was on the box and I also just sent you a PM.

Geoff.
Forum: Altair 8800 07-16-2009, 02:51 PM
Replies: 20
Views: 6,312
Posted By Geoff Harrison
I don't know if you can. Like MBL, it may be...

I don't know if you can. Like MBL, it may be hard coded to port 1.

As for your current loop problem, I'm not sure what else to suggest other than sending the card back and I'll do my best to...
Forum: Altair 8800 07-16-2009, 03:23 AM
Replies: 20
Views: 6,312
Posted By Geoff Harrison
I'm not sure how to use the AdvMon. I got it to...

I'm not sure how to use the AdvMon. I got it to respond to 5 commands: Mxxxx, Wxxxx, Exxxx, Rxxxx, Gxxxx, where xxxx is a 4 digit hex address. The only one that did anything useful for me was M...
Forum: Altair 8800 07-16-2009, 01:02 AM
Replies: 20
Views: 6,312
Posted By Geoff Harrison
Tom, You said earlier that you checked the...

Tom,

You said earlier that you checked the teletype by connecting it to a PC. Does that mean you have a current loop port on your PC?

Geoff.
Forum: Altair 8800 07-15-2009, 11:47 PM
Replies: 20
Views: 6,312
Posted By Geoff Harrison
No, unfortunately I don't have any current loop...

No, unfortunately I don't have any current loop devices. I did verify that the 6850 was working correctly by connecting a TTL/RS232 adapter to its Tx/Rx pins, so if there's a problem it must be with...
Forum: Altair 8800 02-09-2009, 01:40 PM
Replies: 28
Views: 25,460
Posted By Geoff Harrison
Not too long, less than a day. It helped that I...

Not too long, less than a day. It helped that I had previously done the same thing to the 2nd stage tape loader and about half of the MBL is taken directly from that.



Sorry, Marty, I haven't...
Forum: Altair 8800 02-08-2009, 11:59 PM
Replies: 28
Views: 25,460
Posted By Geoff Harrison
Grant posted a hex dump of MBL some time ago in...

Grant posted a hex dump of MBL some time ago in the files section of the Yahoo altaircomputerclub. I recently disassembled that back to source and added some comments. Take a look at:
...
Forum: Altair 8800 02-07-2009, 09:40 PM
Replies: 28
Views: 25,460
Posted By Geoff Harrison
I have a tape image of ALTAIR BASIC 5.0 [14JUL78]...

I have a tape image of ALTAIR BASIC 5.0 [14JUL78] [DISK EXTENDED VERSION], I don't remember where I got it from, and it starts at 0000h. It's not a straight binary image, it needs to be loaded with...
Forum: Altair 8800 01-31-2009, 01:16 PM
Replies: 29
Views: 14,319
Posted By Geoff Harrison
Dave Dunfield...

Dave Dunfield (http://www.classiccmp.org/dunfield/) has a copy on line. Click on the S100 link.

Geoff.
Forum: Altair 8800 01-09-2009, 11:18 PM
Replies: 1
Views: 1,990
Posted By Geoff Harrison
I've never looked at the signals on the bus to...

I've never looked at the signals on the bus to see how noisy they are, but I've run my unterminated 18 slot machine for days at a time with boards all grouped together at one end as well as spread...
Forum: Altair 8800 01-03-2009, 01:36 AM
Replies: 13
Views: 115,075
Posted By Geoff Harrison
If you wire the port as per the MITS manual you...

If you wire the port as per the MITS manual you end up with an odd hybrid DTE/DCE port. Tx and Rx are set up as though it is a DCE, but it uses the control lines as though it is a DTE. The 6850...
Forum: Altair 8800 12-25-2008, 04:49 AM
Replies: 13
Views: 115,075
Posted By Geoff Harrison
Congratulations, you're in for a lot of fun over...

Congratulations, you're in for a lot of fun over the next few weeks.



One quick observation: when Grant's instructions disagree with MITS's, make sure you give precedence to Grant's. I just...
Showing results 1 to 25 of 104

 
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