UK101 Cegmon dump request

[IanB]

Does anyone here have a UK101 with an original copy of Cegmon (i.e. not one downloaded from the net?)
I've been looking at all the various monitors available for download and after filtering all the duplicates I can't find a copy of Cegmon for the standard 48x16 screen. There are 3 different versions of Cegmon that will work with the UK101 but they have different screen dimensions and other quirks that may mean they have been tweaked from the original (there are other copies for the various OSI boards). I have patched a copy of Cegmon to work correctly but I'd like to see a dump from an actual copy if possible.

The three I found are:

CEGMON.ROM
This has a screen of 48x28 with a 2 line offset at the top and would be more suitable for a 60Hz superboard with the 2K screen mod

CEGMONUK16.ROM
This has a screen of 48x14 with a 2 line offset at the top so is more restricted than all the other UK101 monitors that have 48x16 screens

CEGMONUK32.ROM
This has a screen of 48x32 but also has the IRQ and NMI vectors pointing to 0x0235 and 0x0237 respectively which doesn't really make sense because that would only leave 2 bytes for IRQ code before the NMI code (they are not vectors but the addresses that IRQ & NMI will jump to)

The cegmon manual gives the default UK101 values for TOP and BASE of 0xD00C & D3CC respectively and these values indicate a 16 line screen:

(The above 48x14 line ROM has TOP and BASE of 0xD08C & D3CC which confirms 14 lines not 16)

If you are unable to read EPROMS, perhaps you could examine the following memory locations using the Cegmon monitor and post your values:

F954: 34 BF
F955: 02 01
FB8B: D8 D4
FBBD: 0C 8C
FBBF: CC 4C
FBC0: D7 D3
FE3B: D7 D3
FE62: 08 04
FF0D: 20 8C
FF0E: D1 00
FF0F: FF 02
FFE0: 4D CC
FFE2: 01 00
FFFA: 37 30
FFFB: 02 01
FFFE: 35 C0
FFFF: 02 01

They might be one or other of the above values or something else entirely

EDIT:

Also a dump of the Superboard II version of Cegmon from an original EPROM would be useful as the versions online seem to similarly have incorrect values for TOP and BASE

[Pernod]

Does anyone here have a UK101 with an original copy of Cegmon (i.e. not one downloaded from the net?)

I also have a few variants gathered from various places, but the attached is marked orig, so presumably original?

[IanB]

I also have a few variants gathered from various places, but the attached is marked orig, so presumably original?

No, that's not it, there are other variants of Cegmon available for download but they are all for the Superboard or other Ohio Scientific systems like the C2/C4 etc.
That one is an Ohio Scientific C2 with 64x28 screen, not the UK101 or Superboard II.

[peterw810]

Hi,

I bought a UK101 kit from Comp Shop back in 1979 or 1980.
Later I sold it to my friend who installed CEGMON in the early 80s.
I made a back up of the EPROM at the time.
If my memory is correct, it must have been an original...

[BigEd]

Thanks - and welcome to the forum!

[Osi]

I had a look into an older archive file of mine and found a Cegmon0 Rom file. Not sure where this came from, probably from Ian McLaughlins Emulator back in 1998....

[uk101fan]

Hi Ian did you find what you were looking for?
I have a 48x16 CEGMON installed in my UK101 (I assume it is as that's what the sticker says!)

[IanB]

Sorry I haven't checked this thread since before Christmas so only just noticed there have been some updates to my request.

Both of the above ROMs posted recently have some different bytes to all the ROMs found previously:

CEGMON.ROM posted by peterw810 is 48x28 so is the same dimensions as one of the ones I mentioned above but again a few bytes are different to that one.

CEGMON0.ROM posted by Osi is 48x16 so is the first version found with the correct dimensions for the unmodified UK101

I think it's possible that multiple different variations of the ROMs were shipped over the years.

Thanks to peterw810 and Osi for posting

Hi Ian did you find what you were looking for?
I have a 48x16 CEGMON installed in my UK101 (I assume it is as that's what the sticker says!)

Perhaps you could post yours as well to see if it is different again.

[uk101fan]

Hi Ian,

here is a copy of my CEGMON:

Neil.

[IanB]

here is a copy of my CEGMON:
Neil.

Thanks for posting.
It is indeed another full 48*16 version like CEGMON0.ROM but again some bytes are different:

Code: Select all

Comparing files Cegmon0.rom and CEGMON-48X16.ROM
00000154: 34 BF
00000155: 02 01
000003C2: 8C 0C
000003C5: 8C 0C
000003CB: 8C 0C
0000070D: 20 8C
0000070E: D1 00
0000070F: FF 02
000007E0: 4D CD
000007E2: 01 00

[IanB]

I've done a brief comparison of the CEGMONs posted recently and found the following:

Cegmon0.rom posted by Osi:

This is 48x16 and unsurprisingly the major differences concern the screen dimensions but as mentioned above, some CEGMON images have the IRQ and NMI changed to point to 0x235 and 0x237 rather than the original 0x1C0 and 0x130 used by MONUK01 and NEWMON. This seems to have been some attempt to move the interrupt handlers out of the stack page and into the first free bytes in page 2. However it was done incorrectly as the addresses are the start of code execution rather than two byte vectors, so you would need at least 3 bytes between the IRQ and NMI addresses to insert a suitable JMP instruction and thus these changes would cause problems with an NMI handler which would jump into the last byte of the IRQ jump instruction.

With Cegmon0.rom, the IRQ and NMI vectors point to the original 0x1C0 and 0x130 addresses but when you set a breakpoint in the machine code monitor, the IRQ handler for the breakpoint is copied to 0x235 rather than 0x1C0 so this seems to be a hybrid / incompletely patched version and it crashes due to this when using breakpoints so this version is not recommeded for use.

CEGMON-48x16.rom posted by uk101fan:

This is only 5 bytes different from the 48x14 version mentioned in my initial post and those changes just concern the window size with the IRQ, NMI and breakpoint handler all using the original addresses. However, judging by uk101fan's other UK101 posts about the RAM expansion, it looks like his machine is the one that was on ebay recently (please correct me if I'm wrong) which ultimately came from a collector/restorer who had passed away and the photos show the CEGMON on that machine with a recent looking handwritten label so it could possibly be a patched version of the 48x14 variant.

CEGMON.ROM posted by peterw810

This is 48x28 so not the 48x16 I was looking for but it is different yet again to the 48x28 already available on the internet as it has the original IRQ, NMI and breakpoint addresses rather than the page 2 incorrect versions. As peterw810 mentions this is likely an original dump it is possible that the 48x28 and 48x14 were original variants and they later changed to 48x32 and 48x16 or vice-versa (The manual found online indicates that 48x16 was available at some point).

So, thanks to all concerned for contributing but I think the hunt for a confirmed dump of an original 48x16 ROM goes on although uk101fan's version is certainly the best one to use so far.

[uk101fan]

Hi Ian, you are correct, recent purchase from eBay. I've been looking for a board without too many mods for a few years now. I built one back when they first came out but have no idea what happened to it.

[lininjim]

Ian, apologies if this has been answered elsewhere but are you still making the RGB2HDMI stuff?
I'm after a set for my Atari 800XL.
If not, I'm sorry to have troubled you mate.

Cheers
J

[IanB]

Ian, apologies if this has been answered elsewhere but are you still making the RGB2HDMI stuff?
I'm after a set for my Atari 800XL.
If not, I'm sorry to have troubled you mate.

I'm not making boards any more but I am working with a few sellers linked in the RGBtoHDMI wiki.
The Atari 800XL is not directly compatible with RGBtoHDMI as it has composite video out of the chip but it can be made compatible using one of c0pperdragon's lumacode boards which picks up digital signals and encodes them into 'lumacode' which RGBtoHDMI can decode back into a bit perfect image.

Links here:
https://github.com/IanSB/RGBtoHDMI/wiki ... s-for-sale