Amstrad Mega PC / Amstrad Mega PC Plus

[Shakey_Jake33]

No SCART here unfortunately. We have composite with RCA jacks - they aren't that bad though.

They really are!

[Druid II]

Ok, I've stripped the newer of the two TeraDrive units down and taken some good pictures of the board:
http://nemesis.hacking-cult.org/Mega...res/index.html
Most of the chips seem the same as the normal Mega Drive. The FM chipset in this case is a discrete YM3438, which we know is effectively the same as the YM2612. Apart from that, you've got your standard 315-5313, 315-5364, and 315-5309, same as an early model 1 Mega Drive. Probably the two most interesting chips on the board are U18 and U20. U18 has its board label partially covered by the green wires in those pictures, but it's labeled as "BUS SW". U20 is labeled as "DISP SW", and the writing on the chip didn't really turn out in the photos, but its markings are as follows:
NEC JAPAN
(C) IBM
9050KP004
79F2662

These two chips probably handle all communication between the two systems. I haven't traced any connections, but I think it's quite likely that the PC hardware is able to halt the M68000, and read/write into the Mega Drive RAM at the very least.

Hot pictures.

[limboy777]

Hi retro junkie/shane

Can you tell me if the Disk on module you pruchased requires a seperate power supply? or did you just have the power connector for the hard drive disconnected. (does it run a lot faster than the hard drive i.e is it comparable to the difference between ssd and standard ide or is is just the same?)

I think the maximum hdd capacity is 504mb is this correct. (I know you have used drive overlay software).

Also can you connect another hard drive as a slave?

Also in terms of the memory - do the chips have to match in terms of brand etc (have you upgraded to 16mb ram?). Would any 30 pin edo ram at 4mb max work in the slots?

[masorgu]

I used to have a mega pc since new but they have a common problem with battery leakage destroying all the components making it workthless. Most of the mega pc's for sale on ebay etc have an issue with starting up as more than likely the battery has died and leaked and caused damage. The battery is soldered on so most ordinary folk will not remove it unless and store the computer slowly killing it. As time passes, different components fail as the motherboard tracks are eaten by the acid.

The same thing happened with my friends mega pc which he bought second hand.

They are also practically very hard to upgrade from a crippled 386 spec unless you are lucky enough to find a similiar amstrad board like retrojunkie.

[RetroJunkie]

Hi retro junkie/shane


Can you tell me if the Disk on module you pruchased requires a seperate power supply? or did you just have the power connector for the hard drive disconnected. (does it run a lot faster than the hard drive i.e is it comparable to the difference between ssd and standard ide or is is just the same?)


I think the maximum hdd capacity is 504mb is this correct. (I know you have used drive overlay software).


Also can you connect another hard drive as a slave?


Also in terms of the memory - do the chips have to match in terms of brand etc (have you upgraded to 16mb ram?). Would any 30 pin edo ram at 4mb max work in the slots?

The DOM uses the standard four pin 3.5" hard drive molex power connector - however I was not able to have much luck with the Mega PC (386SX) and it detecting hard drives. The 486SLC solved all that with it's nice flash looking modern BIOS and working date/time battery.


Now I am not sure why the 386SX would not detect hard drives properly - I bought a whole bunch varying from 20MB up to 500MB. I've since bought a power supply for the 386SX board to test further. It's possible the battery acid damaged the hard drive controller since it was all over the shop.


There is definitely the option of secondary hard drive as both BIOSes on the 386SX and 486SX have a space for it. I'd need a double adapter for power, which I now have... Although for me putting that in seems a bit of overkill for the time being. If I can get the 386SX cranking I'll try it with two drives definitely.


From what I could tell they did need to be paired - two by two hurrah! I had no success with anything above 4x4MB though. It's not EDO though, just old fashioned 30 pin SIMMs

I used to have a mega pc since new but they have a common problem with battery leakage destroying all the components making it workthless. Most of the mega pc's for sale on ebay etc have an issue with starting up as more than likely the battery has died and leaked and caused damage. The battery is soldered on so most ordinary folk will not remove it unless and store the computer slowly killing it. As time passes, different components fail as the motherboard tracks are eaten by the acid.

The same thing happened with my friends mega pc which he bought second hand.

They are also practically very hard to upgrade from a crippled 386 spec unless you are lucky enough to find a similiar amstrad board like retrojunkie.

It's damn unfortunate that the motherboards aren't tape to the cover of the Mega PC. I saw a photo of one that had been stored upside down and the battery had leaked onto the case and not the motherboard - lucky break!

The best thing about the 486SLC (or worst thing) is that it uses a coin cell battery buried in a Dallas DS1287. Once the battery goes flat you can hack it apart and attach an external battery or try to find a replacement DS1287. Thankfully they still seem to make them or at least variations of them. The DS12887 and DS1287A / DS1287A+ all seem to work well. Just be wary of the date codes on the blighters. I had a seller ship me one that was older than my 20 year old one. Obviously the battery was dead. Since then I have come across one made late 2011 and late 2009 - both of these work OK for now.

I'l be able to hack apart one or two and perform the battery mod though for a more permanent solution.

[limboy777]

Hi retrojunkie

Thanks for replying to all my questions. I have bought a mega pc after much searching. There is some info which may interest you if you are going to fix/upgrade your 386 board.

My megapc game with a 486 srx50 chip on it! It is branded 386 sx on the casing DSC00968.JPG

[limboy777]

It seems cyrix developed a chip that goes over the 386 (clips over it) to double the speed of the processor, add 1kb cache and add 486 instructions to it. Mine also came with 8mb ram and runs pretty quick in windows 3.1. (before I bought it, I was going to put deli linux on it which apparently works well with really really old computers). However the 1kb cache for the 486 upgrade needs some kind of software installed before dos boots up and this is installed on the 40mb hard drive which I was going to replace (hence my question on fitting two hard drives as I want to leave the software installed).

Apparently there is a line of cyrix/texas instruments chips titled 486 DLC/SLC that can be fitted onto 386 motherboards as a straight pin for pin replacement, the only problem being that you would have to desolder the 386 chip and replace it. (maybe your soldering friend can have a look if its feasible on the damaged 386 board you have?). you can google it or I can upload the links of the research I did prior to the purchase of my mega pc.

Mine seems to not recognise the ps2 mouse at the moment but recognises the serial mouse fine. Should the mouse work out of the box? or did you have to reload drivers onto your new DOM?

On reading your various posts on your website, I noticed that you mentioned that the video ram is maxed out. I think these came with 256k as standard (does yours have 512k?) Where is this located and isit a replacement or is there a spare slot? (can you upload a picture) I have only taken of the metal casing and removed the hdd and fdd to have a look. (Ive not stripped it apart as of yet).

I am wondering if you can add an ISA video card and switch of the on board video? or would this affect the vga out?

Lastly in terms of your network card, I am assumming that a standard ISA ethernet network card will suffice (is yours plug in and play or did you need drivers?)

Anyway hope you dont mind me hijacking your thread, I am following in your footsteps of upgrading the mega pc! Hopefully we can help each other (you help me more than me help you!)

[RetroJunkie]

It seems cyrix developed a chip that goes over the 386 (clips over it) to double the speed of the processor, add 1kb cache and add 486 instructions to it. Mine also came with 8mb ram and runs pretty quick in windows 3.1. (before I bought it, I was going to put deli linux on it which apparently works well with really really old computers). However the 1kb cache for the 486 upgrade needs some kind of software installed before dos boots up and this is installed on the 40mb hard drive which I was going to replace (hence my question on fitting two hard drives as I want to leave the software installed).

Apparently there is a line of cyrix/texas instruments chips titled 486 DLC/SLC that can be fitted onto 386 motherboards as a straight pin for pin replacement, the only problem being that you would have to desolder the 386 chip and replace it. (maybe your soldering friend can have a look if its feasible on the damaged 386 board you have?). you can google it or I can upload the links of the research I did prior to the purchase of my mega pc.

Mine seems to not recognise the ps2 mouse at the moment but recognises the serial mouse fine. Should the mouse work out of the box? or did you have to reload drivers onto your new DOM?

On reading your various posts on your website, I noticed that you mentioned that the video ram is maxed out. I think these came with 256k as standard (does yours have 512k?) Where is this located and isit a replacement or is there a spare slot? (can you upload a picture) I have only taken of the metal casing and removed the hdd and fdd to have a look. (Ive not stripped it apart as of yet).

I am wondering if you can add an ISA video card and switch of the on board video? or would this affect the vga out?

Lastly in terms of your network card, I am assumming that a standard ISA ethernet network card will suffice (is yours plug in and play or did you need drivers?)

Anyway hope you dont mind me hijacking your thread, I am following in your footsteps of upgrading the mega pc! Hopefully we can help each other (you help me more than me help you!)

Wow! Talk about a good find! That clip on CPU upgrade looks pretty magical to me! I had no idea those things existed. PS/2 mouse should recognise straight provided some drivers are loaded for it in DOS - I think... I haven't actually loaded Windows 3.11 onto either of the Mega PCs yet, I just need more hours in the day

Here's the RAM upgraded on the 486SLC here and the 386SX VRAM and an empty socket can be seen here - I haven't tested the 386SX board with the additional VRAM though - I do not even know if I bought the right chips yet... That's another reason I picked up a cheap AT PSU for testing this further

As for ethernet, mine was plug and play under Windows 95, however under 3.11 it might be a different story - again just another thing to try out on my to do list. I've got two ISA network cards now to test with too.

I will definitely be looking into these clip on CPUs and perhaps even replacing the CPU chip with a pin compatible 486-esque chip. And don't worry about hijacking this thread, it's here for future reference for anyone who comes across these fantastic machines.

Good find on the CPU clip on chip though! Very nice! Fastest Mega PC I know of!

Edit: How was the NiCad battery looking in your one?

Edit 2: Oh yeah! The ISA video card - Good question raised there, I know there is a separate jumper on the motherboard to determine if internal video or a video card is used (three pins one jumper) near the VRAM if I remember correctly - unless someone else has tried it the only way to find out is to give it a try

[limboy777]

Hi Retrojunkie

I have about 20 computers/consoles and the amstrad mega pc is my favourite (only had it a few days)! Mine seems to be fine re battery but I will replace it using standard 2032 rechargable batteryand getting someone to solder it. There was a little bit of leakage from the battery but it seems it has been stored upside down and therefore any acid has dripped onto the casing. (i have cleaned it up and left it upside down - see pic). It stores the time/date and loads windows. (ive only used it for about 20 mins and then spent the last few days cleaning it and the various parts).

Mine also doesnt have much yellowing although there is some damage to the plastic front panel.

Also I dont have a monitor yet but I always get what I want eventually (I bought a mega pc pad before I even saw a mega pc for sale as I knew I would get one eventually (Ive looked at options mentioned on this thread but would prefer the real thing).

Are your network cards ne2000 compatible as this is what Im looking at?

Re the VRAM - you can experiment and then I will buy what I need after you tell me what to buy!!!

Re windows 3.1, it runs quite well in mine with no lagging but I would be interested in seeing Deli linux setup (or something just as small). If I get a compatible hard drive, I will test it and see how it runs. Link here of some old posts:

http://www.linuxquestions.org/questi...-8-etc-681737/

There seems to be some floppy images of deli linux.

I think if the ISA video card can be upgraded then it will open up quite a lot of opportunities to increase the performance of the machine.

Just saw you Terradrive purchase - would love to see what you do with that! you lucky......

[RetroJunkie]

Hi Retrojunkie

I have about 20 computers/consoles and the amstrad mega pc is my favourite (only had it a few days)! Mine seems to be fine re battery but I will replace it using standard 2032 rechargable batteryand getting someone to solder it. There was a little bit of leakage from the battery but it seems it has been stored upside down and therefore any acid has dripped onto the casing. (i have cleaned it up and left it upside down - see pic). It stores the time/date and loads windows. (ive only used it for about 20 mins and then spent the last few days cleaning it and the various parts).

Mine also doesnt have much yellowing although there is some damage to the plastic front panel.

Also I dont have a monitor yet but I always get what I want eventually (I bought a mega pc pad before I even saw a mega pc for sale as I knew I would get one eventually (Ive looked at options mentioned on this thread but would prefer the real thing).

Are your network cards ne2000 compatible as this is what Im looking at?

Re the VRAM - you can experiment and then I will buy what I need after you tell me what to buy!!!

Re windows 3.1, it runs quite well in mine with no lagging but I would be interested in seeing Deli linux setup (or something just as small). If I get a compatible hard drive, I will test it and see how it runs. Link here of some old posts:

http://www.linuxquestions.org/questi...-8-etc-681737/

There seems to be some floppy images of deli linux.

I think if the ISA video card can be upgraded then it will open up quite a lot of opportunities to increase the performance of the machine.

Just saw you Terradrive purchase - would love to see what you do with that! you lucky......

Boom! This ethernet card works well in Windows 95, the other one in my photo gallery here did nothing but overheat and not detect. I did get a replacement as it looked to be DOA from the seller - big dent in the crystal oscillator chip there... The replacement card doesn't have that and I'll give it a go. I am definitely going to go home for the weekend and tinker with these toys!

Hey, what do you know - I started off with an Amstrad Mega PC Control Pad too! I've got the joystick en route from the UK as we speak. I need to fix my monitor up though it definitely has some issues.

Ah the TeraDrive, sure is a heavy brick compared with the Mega PC - should be an interesting project once the step down converter arrives. EMS Japan is far too fast for our local post services here in Australia.

I'll give the VRAM a test too and see what happens - for all I know it should work, but at the same time it might as well just fry it completely. Will keep you posted - Fun fun fun!

[limboy777]

Forgot to mention there are two voltage ranges for the cyrix chips 5v and 3.3v. I think the 5volt version is for desktops.

Also I remember bidding on Amstrad joystick recently (did you purchase it on ebay uk?)

[RetroJunkie]

Forgot to mention there are two voltage ranges for the cyrix chips 5v and 3.3v. I think the 5volt version is for desktops.

Also I remember bidding on Amstrad joystick recently (did you purchase it on ebay uk?)

Guilty! Got it today in the post. The good old AJ-5, a lot smaller than I was expecting but works well for such a small joystick. Did I snipe you out? No hard feelings I hope?

[limboy777]

Re Amstrad Joystick: Yep you sniped me! I was looking in completed listings and it was unsold at 99p so I sent the guy a message asking him if he still had it as I would buy it direct via paypal. He just relisted it and told me about it. I thought no one else would bid and tried to persuade him to end the auction early but he didnt! And the rest as they say is history. Small world and no hard feelings (ive already got one - just being greedy in case I got another mega pc).....


....which I did.. Won another one today (I sniped someone else!! ) This one comes with the monitor but nothing else and has a faulty power switch. Im going to take the monitor for mine and swap the front fascia as my original one is damaged. Im then going to try to fix the power switch on the new one and will change the batteries on both with rechargable cr2032 battery and holder (found someone local to me who will do the work - hes a former tv repair guy so maybe able to help with power switch). I doubt this one will have any upgrades like mine did but if it does bonus!

The only thing missing from my main unit is the original amstrad keyboard however I managed to pick up an exact same type (unused) without the amstrad logo for £2 from a car boot. I noticed yours is missing a key in one of your videos (should be easy to find another generic keyboard and pop in the missing key into yours).

BTW I noticed something clear underneath my battery on mine (didnt notice before and was woried it was a leak I hadnt spotted but then went through your galery which confirmed that it was glue underneath the battery. So thanks for all the pics.

Also you memory chips look different to mine, not had a chance but will open up and post some pictures.

[Hedgeyourbets]

Haha, I was one of the bidders on that one today, a little disappointed, but probably best I didn't win, I tend to bid on things I cant afford.

[limboy777]

Ive started a photo album as I cant seem to upload anything here.

http://s1269.photobucket.com/albums/...d%20Mega%20PC/

[limboy777]

Hedge your bets - You didnt bid in the last minute did you? - you increased the price by quite a bit!

Im not going to bid on any more if they do turn up as I needed this one for the monitor and front fascia

[Hedgeyourbets]

haha, nah, if I had bid at the last minute, you can bet I would have won (and then regretted it for weeks), the other week I got so pissed off with being bid sniped, I bid £400 for a copy of dynamite cop on the Dreamcast, I won it for £10 lol :P

[WolverineDK]

This is a smashing great thread. I remember one of my rather old posts, I had thoughts about "what if you upgrade either a terradrive or a megapc ?" And I got quite the opposite reactions from some people with my thoughts. No I do not own either machine. I am some times just a dreamer who imagines what can be done, and at the time I considered myself thinking out of the box. So I applaud you two guys for doing something awesome :) hey what about doing solid state drives with the machines ? it is just a thought :) anyway thanks for a lovely read :) oh yeah, does any of you know "Tezza" and his blog about his old computers ? perhaps he could either help you now or in the future. Cause here is his blog by the way.

http://www.classic-computers.org.nz/blog/index.htm

Sorry if I am just babbling away. Great thread :)

[RetroJunkie]

Re Amstrad Joystick: Yep you sniped me! I was looking in completed listings and it was unsold at 99p so I sent the guy a message asking him if he still had it as I would buy it direct via paypal. He just relisted it and told me about it. I thought no one else would bid and tried to persuade him to end the auction early but he didnt! And the rest as they say is history. Small world and no hard feelings (ive already got one - just being greedy in case I got another mega pc).....

....which I did.. Won another one today (I sniped someone else!! ) This one comes with the monitor but nothing else and has a faulty power switch. Im going to take the monitor for mine and swap the front fascia as my original one is damaged. Im then going to try to fix the power switch on the new one and will change the batteries on both with rechargable cr2032 battery and holder (found someone local to me who will do the work - hes a former tv repair guy so maybe able to help with power switch). I doubt this one will have any upgrades like mine did but if it does bonus!

The only thing missing from my main unit is the original amstrad keyboard however I managed to pick up an exact same type (unused) without the amstrad logo for £2 from a car boot. I noticed yours is missing a key in one of your videos (should be easy to find another generic keyboard and pop in the missing key into yours).

BTW I noticed something clear underneath my battery on mine (didnt notice before and was woried it was a leak I hadnt spotted but then went through your galery which confirmed that it was glue underneath the battery. So thanks for all the pics.

Also you memory chips look different to mine, not had a chance but will open up and post some pictures.

Hahaha I hate it when sellers do that! I won a Mega Drive arcade stick like that though. I had already won their other auction at cost and then I missed the other item (which had no bids either) and they said sure you can have a go and they relisted it for TEN DAYS. They had free shipping anyway.... So I got it at the listed value. Poor sellers! Sometimes they advertise so badly!

Oh that keyboard was just a loaner - It is hard to find a keyboard for these. I have given up looking for now since I have some bodgy IBM PS/2 keyboard - not the nice clicky ones though...

Damn! You will have more Mega PCs than cents if you keep this up hahaha! Kind of wish I was in the UK area since we have pretty much none over here.

I just had a look at your album too... errr you have to work out macro mode on your camera! There's more blur than [insert something that blurs a lot].

haha, nah, if I had bid at the last minute, you can bet I would have won (and then regretted it for weeks), the other week I got so pissed off with being bid sniped, I bid £400 for a copy of dynamite cop on the Dreamcast, I won it for £10 lol :P

YIKES, sounds like you really want Dynamite Cop! I love it when that happens though, put in a ridiculously high max bid in the last 10 seconds and wham, you get it for peanuts

[RetroJunkie]

This is a smashing great thread. I remember one of my rather old posts, I had thoughts about "what if you upgrade either a terradrive or a megapc ?" And I got quite the opposite reactions from some people with my thoughts. No I do not own either machine. I am some times just a dreamer who imagines what can be done, and at the time I considered myself thinking out of the box. So I applaud you two guys for doing something awesome :) hey what about doing solid state drives with the machines ? it is just a thought :) anyway thanks for a lovely read :) oh yeah, does any of you know "Tezza" and his blog about his old computers ? perhaps he could either help you now or in the future. Cause here is his blog by the way.

http://www.classic-computers.org.nz/blog/index.htm

Sorry if I am just babbling away. Great thread :)

I've never come across that site, but boy does he know how to fix! He is on a different level to me, I just board fit!
What reaction were you getting? Were they all conservationists or something? Did they grade theirs and put it in a perspex box with 85 on it?