DOS not booting

[bxdanny]

Dave,

The disk images in the ZIP file attached to this message show what I am talking about. The one called "OS-65D v3.2 (NMHZ)" is (I think) the standard version of that OS. The one called "EdSec5" is the version I modified. (BTW, is .ZIP the ONLY extension that is allowed to be posted here?)

Writing to $DE00 selects 32 or 64 character screen width (and also, it seems, enables or disables color on systems equipped for it), but reading from it does not return the value written, but something else entirely. I never saw any written documentation mention it, but I do seem to remember seeing the circuit on a schematic of the 540 board. If I remember right, when a read of $DE00 was done, a buffer would be enabled that connected the horizontal sync line to bit 7 of the data bus. I think all the (non-C1P) 5" disks of 65D 3.2 and 3.3 look at that port to gauge the speed of the system they are running on. 8" disks didn't do that, since they had to run on serial systems too.

[MK14HAK]

The standard OSI 5.25" versions of 65D for the C2/C4

Your referring to v3.3 I guess Danny with the TK6 loading via the $2E78- code. LDA $DE00 seems to be used in v3.3 to determine NMHZ, your right.
Ill check if the ($267B) value comes into play in loading tk1 for v3.2 . That may be my problem with the media boot.

The standard OSI 5.25" versions of 65D

I wish I new what was what with the different versions. In particular there seem to be a couple of 3.2 versions ? Which was the last 3.2 version or is it just the application of the "adaptive step rate patch" that makes these different. ?

[dave]

Dave,

The disk images in the ZIP file attached to this message show what I am talking about. The one called "OS-65D v3.2 (NMHZ)" is (I think) the standard version of that OS. The one called "EdSec5" is the version I modified. (BTW, is .ZIP the ONLY extension that is allowed to be posted here?)

Writing to $DE00 selects 32 or 64 character screen width (and also, it seems, enables or disables color on systems equipped for it), but reading from it does not return the value written, but something else entirely. I never saw any written documentation mention it, but I do seem to remember seeing the circuit on a schematic of the 540 board. If I remember right, when a read of $DE00 was done, a buffer would be enabled that connected the horizontal sync line to bit 7 of the data bus. I think all the (non-C1P) 5" disks of 65D 3.2 and 3.3 look at that port to gauge the speed of the system they are running on. 8" disks didn't do that, since they had to run on serial systems too.

Interesting--it's different code from my OSI boot disks. I see the testing of DE00, as you indicated. I have never been aware of such a signal on reading DExx, and have not seen that circuit, even reviewing the schematic in light of this information.

The /SE signal is asserted when a valid $DExx address is on the bus. On the 540A, I only see this setting a couple of D flip-flops on the low 2 bits, and on the 540B, I see this clocking a register on the low 4 data bits. I can't find anything obvious active when a read is attempted. I certainly could be overlooking it. Any clues?

[bxdanny]

Dave,

I no longer have the 540 schematics. If you want, email them to me or attach them to a PM. What I would look for would be something attached to data bus bit 7 only, and not the whole bus, or look at the sync signals and see what they are connected to.

[Klyball]

OSI540B Video Board

Model 540B video board © 1978

Supports 32x32, and 64x32 video modes with color, 542 keyboard interface socket Character memory $D000-D7FF each display row always $40 bytes long Color memory $E000-E7FF 4bits. 
bit 0: 0= normal(bright txt, color background), 1= inverse(dark txt, bright background) 
bit 1-3: 0=yellow, red, green, olive, blue, purple, sky blue, black 

Write Register @ $DE00 controls video modes: 
bit 0 1=32, 0=64 
bit 1 1=tone on (542 keyboard) 
bit 2 1=color on 
bit 3 1=enable 38-40Khz AC Home control output 

Read Register @ $DE00 
bit 7 = video timing counter bit, 0 for 1/120 second, 1 for 1/120 second, based on video clock (60Hz)

OSI540B schematics

http://osi.marks-lab.com/boards/schematics/OSI540B.pdf

[bxdanny]

Thanks Klyball! I didn't realize, or had forgotten, that Mark's site had that much detail on all the boards. So the signal we were talking about is related to the vertical sync, not the horizontal, but is a squarewave.

[dave]

Dave,

I no longer have the 540 schematics. If you want, email them to me or attach them to a PM. What I would look for would be something attached to data bus bit 7 only, and not the whole bus, or look at the sync signals and see what they are connected to.

Schematics are on the web site:

http://osiweb.org/manuals/540A.pdf

http://osiweb.org/manuals/OSI_540B.pdf

I coudln't find the buffer. I looked longer at the 540A schematic (with which I'm more familiar) than the 540B schematic, so perhaps this was added on the 540B, but I still didn't find it on the 540B. I'm looking for a tristate buffer to D7 enabled by /SE and R/W, but perhaps there's another mechanism. Can you point out where this is implemented? Many thanks to Grant and Danny for bringing this interesting feature to light. I was totally unaware of it. I'm hoping it was added on the 540B, since I thought I was familiar with the 540A, and never knew of it!

Dave

[bxdanny]

Dave,

I think it's the signal marked KD7 on the bottom right of sheet 1. It connects to the 8T26 on the bottom left of sheet 4. Yes, it took a while to figure that out.

Anyway, as Klyball pointed out (or rather quoted from), it is mentioned in the description of the 540 on Mark's site, and it is a square wave at the vertical sync frequency (60 Hz), not the horizontal.

[dave]

Yup, there it is. So it was added on the 540B, which explains why I never encountered it (my system has a 540A). I guess that means that the NMHz version won't work on a C2, which is why it's not on my 65D disks. I somehow missed the note on Mark's site as well.

This has been a most interesting thread--thanks Danny and Jeff.

Dave

[MK14HAK]

OS65D V3.3 disk images for C1PMF:

If your looking for "Original" C1PMF Disks, they may be found along with the winOSI emulator software on Mark's site:
http://osi.marks-lab.com/