XT/CGA laptop dissection

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Re: XT/CGA laptop dissection

Postby bjt » 2014-8-21 @ 12:42

Covox clone arrived and looks good, uses low tolerance resistors. There's a mod player which works on 8086 (Galaxy Player) which I'm planning to try.
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Re: XT/CGA laptop dissection

Postby bjt » 2014-8-24 @ 09:53

HxC mounted up and working as drive A and B. Really cool gadget, it even has a little buzzer to make seek noises so you know it's working.

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Re: XT/CGA laptop dissection

Postby bjt » 2014-9-01 @ 10:45

Have been having a blast trying different games on this system. I also finally found a EMM driver that works with the C&T 82C100 chipset, it's the one that Robin4 uploaded with the Laser XT-3 system utilities: http://www.vogonsdrivers.com/getfile.php?fileid=640

This driver allows me to create a ramdrive in the top 384k to store commonly-used programs. With DOS 3.3 I still have 585k left after loading the EMM driver and ramdisk, which seems plenty.

Will probably upload a video in a bit showing various games running, playing MOD files and even driving my SC-55ST via the serial port.
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Re: XT/CGA laptop dissection

Postby bjt » 2015-3-19 @ 11:53

Holy thread resurrect Batman!

With my other machines all sorted I'm coming back to this. I now have an Extron RGB 202xi video converter that should do a better job of the CGA->Analogue RGB conversion than my home-made circuit. Just need to make up some suitable cables and test it out.

First of all though, before I put this away last year I was still having intermittent problems with the battery light flickering on during disk access, and read failures to boot. This continued even when I replaced the floppy with the HxC emulator, so my next suspect was the power supply. Sure enough, some of the supply voltages were well out of spec.

The innards of the PSU. I can't see anything obviously wrong but I'm not about to poke around with that massive cap in there, so time to look for a replacement. Thankfully a kind soul posted a pinout for the power connector at http://www.actsirius1.co.uk/pages/docs/v86p_power.pdf. Note that I found Pin 1 to have voltage on it when I probed the original PSU, so I left it disconnected for the replacement.
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The original PSU is 8.5V with fair whack of current, more than most cheap generic PSUs can supply.
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Luckily it turns out that a Playstation 2 Slim PSU is a perfect match, and these are available cheap on eBay.
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Glued the new PSU inside the old housing with a load of epoxy, it's not going anywhere.
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The final result.
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Re: XT/CGA laptop dissection

Postby carlostex » 2015-3-19 @ 12:30

Amazing work mate. Your XT machine made me remember about the Halt and Catch Fire TV series. You are truly a resourceful chap, i will definitely be bothering you if i ever have the need. :lol:
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Re: XT/CGA laptop dissection

Postby bjt » 2015-3-20 @ 09:34

Cheers! I enjoying messing with this kind of hardware. Amazing what you can get done with a multimeter and a soldering iron.

Currently working on porting the HxC Floppy Selector software to DOS, this is an app that can display an on-screen list of all the disk images on the SD card and allows you to "insert" them to drive A or B. Perhaps this will make the HxC emulator more attractive to PC retro users compared to the cheaper Gotek devices.

https://www.youtube.com/watch?v=p1zP6p9SBLw
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Re: XT/CGA laptop dissection

Postby chinny22 » 2015-3-21 @ 17:22

Missed this the 1st time round. Loving the mix of old and new like HxC Floppy, TV out. Could you use a CF card for a HDD?
Putting the PS2 adaptor inside the original was a nice bit of attention to detail.
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Re: XT/CGA laptop dissection

Postby bjt » 2015-3-23 @ 09:56

The HDD interface is a weird 26-pin proprietary thing based on RLL I think, so a CF card is out of the question unfortunately.

Made some good progress on porting the floppy image selector. Doesn't look like much but it's parsing the FAT32 filesystem on the SD card correctly (DOS 3.3). Still got to get the image selection working.

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Also bonus offtopic pic as it's right here on the camera, went for a walk in the hills on Saturday
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Re: XT/CGA laptop dissection

Postby badmojo » 2015-3-23 @ 21:45

Great project bjt! There's lots of fun to be had with a bit of imagination and persistence.

Nice pic of the countryside, love those old stone fences. A bit of persistence required in building those too. :)
If it's broke, then fix it!
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Re: XT/CGA laptop dissection

Postby bjt » 2015-3-24 @ 21:52

Found something else cool: although the built in BIOS only supports 720k drives, the on-board floppy controller (WD37C65) supports the higher data rates used by 1.44MB floppies.

There is a TSR called 2M-XBIOS which can piggyback onto the system BIOS to add support for HD floppies. Tried this just now and it works a treat, I can mount a 1.44MB image in both A and B. This will open up more games/apps that don't fit on a single 720k floppy image.

Obviously I can only boot from 720k image in A:, but once the TSR has loaded I can switch to a 1.44MB image.

More info: http://www.vintage-computer.com/vcforum ... for-PC-XTs
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Re: XT/CGA laptop dissection

Postby carlostex » 2015-3-25 @ 09:14

^I believe some XT-IDE addon cards can provide some BIOS extensions that include 1.44MB Floppy support, that should be available during boot time.
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Re: XT/CGA laptop dissection

Postby StickByDos » 2015-4-05 @ 02:20

Hello,

I've just seen your topic, I too have a V86P
Its hard disk is still working and it was still carrying the program to generate the reinstallation disks for Victor MS-DOS 4.01a french
It has EMS driver and an utility to switch grayscale dithering mode between 9 modes
Type win to loose the power of your computer !
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Re: XT/CGA laptop dissection

Postby bjt » 2015-4-05 @ 09:51

Hi, that's great news. Could upload the V86P-specific files here or email them to me please?

These are quite cool little machines, do you have any plans for yours?

I have nearly finished porting the HxC floppy emulator manager to DOS, just need to tidy up the interface. I stuck to text mode so it will run on anything from MDA upwards.
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Re: XT/CGA laptop dissection

Postby StickByDos » 2015-4-05 @ 10:46

Here are the files but hard disk has also files for others Victor laptops

On mine, battery still hold charge for 1 hour.
I wish someone could make a special version of XT-IDE for larger hard disk, hd controller is on a daughterboard that could be replaced and hd bios is on a socket on the motherboard.

There is a 60 pins extension connector on the back, I think it's ISA except power, that can be used for extensions.
Attachments
V86P.ZIP
SXTEMM.SYS & GRAYSET.EXE
(8.08 KiB) Downloaded 48 times
Type win to loose the power of your computer !
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Re: XT/CGA laptop dissection

Postby bjt » 2015-4-07 @ 20:33

That EMS driver seems to work well, thanks.

Do you know how to toggle between 4.77Mhz and 10Mhz CPU speeds? I have a feeling it may be CTRL-ALT-F7 or F8.
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Re: XT/CGA laptop dissection

Postby StickByDos » 2015-4-07 @ 23:26

I didn't know this, thanks.
I've just tried and I discovered with C&T MIPS 1.20
CTRL-ALT-F7 4.77MHz (MIPS 0.22)
CTRL-ALT-F8 10MHz (MIPS 0.43)
CTRL-ALT-F9 Invert LCD
CTRL-ALT-F10 Switch off LCD
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Re: XT/CGA laptop dissection

Postby bjt » 2015-4-08 @ 07:08

Ctrl-Alt-F10 switches between internal and external displays. Good to confirm speed switching, that will come in handy for some old games.
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Re: XT/CGA laptop dissection

Postby bjt » 2015-4-15 @ 11:08

Finished porting the HxC manager app from Amiga. More info here:

viewtopic.php?f=24&t=43031
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Re: XT/CGA laptop dissection

Postby keropi » 2015-8-11 @ 08:21

I am resurrecting this thread because of the cga->scart diagram posted by bjt: viewtopic.php?p=374305#p374305

I have seen the schematics floating in the web and I assume this one is the best and without errors. What about that brown/yellow fix? What is it required so this becomes the ultimate converter?
Also since my CGA has a working composite-output, I think I won't even build the sync combiner part, it should make no difference to a crt if I use cvbs as sync.

I just got an XT setup but the monitor is a b/w one... it sucks and I am thinking of replacing it with a triniton 14" that also has separate composite input .
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Re: XT/CGA laptop dissection

Postby StickByDos » 2015-8-11 @ 11:51

According to to there, green intensity is reduced when color 6 is detected.

It can be implemented with logical gates circuitry, 4 inputs, 5 outputs, corresponding to CGA RGBI and an alternate green output with an extra resistor, that is used when color 6 is detected.
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