Hi again i have tryed to replace the vga cable on my amstrad and on 15khz its a loud beep sounds like a fly back or some transforma or something if i could post this to to someone to repair this any uk place would be cool i would be willing to use other 15khz vga montior if i can find a workable one????
that montior is rare now.
Be sure that pin 15 of VGA is wired properly, as it is the one that triggers the VGA/15KHz switch, according to the monitor manual (PC14DSM). Double-check both on the PCB and VGA connector side.
If the noise you hear is like a high-pitched whistle then it's normal, as it is the functioning noise of a CRT running at 15KHz. Put a cartridge and see what happens (if not done already).
Hi i am going to send it away for a someone to fix it i dont want to mess with it any more then i have the high pitched probleam never done it before i know that it did work when i frist had it but then started to go wrong.
Sorry been busy last couple of weeks.
Dioxaz - thanks for all the info on the graphics cards. I was expecting the following to happen;
1. That you could just upgrade the card after changing jumpers and use the mage pc as normal (best scenario)
2. You can only use one side
It seems that you can use one side only or are you going to do further experiments?
An update on where I am (pics in the link below);
- I took the vram chips from one of my ISA graphics cards and put 2 of them in my main mega pc. Used syscheck and my vram is now 512K - the maximum! Cant seem to check it in bios and syscheck seems to be the only one that seems to report on this.
- Did a few tests on my cyrix upgrade chip with syscheck, you can turn the cache on and off and it makes a massive difference - my max syscheck score is 67.8 with the 486 upgrade, 16mb, 512k vram, 1k cache on, large hard drive. I have also made the loadup screen load up the cyrix upgrade screen instead of windows. Also has a benchmarking piece of software which shows that its faster than a Dell i486/33 and slower than a Compaq i486/66.
- Got my LS120 floppy however I broke one of the pins so I will have to repair this!
- Connected a CD-ROM drive and it works fine. (used a ide cable with master slave connectors)
- Installed Calmira - looks ok but need to download v4.00 of calmira xp as I wasnt too impressed with 3.3.
- Installed microsoft works, wolfenstein and loaded up mario on floppy (yes for the pc). Wolfenstein runs smooth on my 486 pc but is slow on the other 386 spec mega pc's I have.
- Installed network card but windows 3.1 didnt like it....
- Got another amstrad joystick in the box and unused!
- Got some software of another chap on another forum that he put together, it installs dos 8.0 (but not windows) as well as other stuff so no more probs with hard drive limits! (unfortunatley I cant release this as I am just a tester for the clever guys software which I will report back on).
Some pics here;
- Waiting for my CF HDD connector and then will connect 2gb and 1gb cf cards in master slave configuration. This should make the syscheck score higher as seek times on cf card should be higher than the 500mb hard drives Ive tested and the spare 80gb hdd I was planning to use. It should also mean a low heat signature as Im worried that the 486 sits right underneath the hard drive and doesnt use a heatsink as standard.
- With the CF installed, I will try an early version of windows 95 along with the network card. If that doesnt work well then delicate linux will be tested.
- Install lots of DOS games when I am happy
- Get a 387 co-processor.
- Contemplating selling some of my spares as I have bought too much and probably paid too much!
Dioxade - Didnt find the 387 that you mentioned on ebay! if you see anything else, please let me know.
Bart - If you have problems with getting the monitor fixed, please report back.
Retrojunkie can I ask if you have a syscheck score for your 486? Also have you looked into 487 co-processors (apparently they disable the main cpu and are basically a 486 chip with cache). Im not sure if they would work with yours as the 486slc is a 386 with 486 instructions added? (similiar to my upgrade chip).
Last edited by limboy777; 06-09-2012 at 04:07 PM.
WOW! You have been busy! I still haven't had any access to my poor Mega PC, only got access to my TeraDrives and just got some working 30MB hard drives! Woohoo! It is so so so so so slow. I can play Crystal Caves well, but games like The Incredible Machine run so slow. Need to decide upon what to put in my ISA slot. Whether it be a network or a sound card. Sound card would make the most sense I suppose but I would like to give Arachne a spin.
Originally Posted by limboy777
I thought those 487 co-processors that made them into DX would work since they needed a i486SX and the package of the chips seems to be very different to the package on the motherboard sadly... if anyone else can prove me wrong I'd be happy to try and hunt one down. Here's the co-processor I ended up going with on the 486SLC.
I'm going to try and get to where my Mega PC is today and tomorrow so I'll do the syscheck and report back. I have a feeling you might be blitzing me though :-) Wait! Hold that thought. Here you go, I already took one! Absolutely obliterated by your ramped up, unstoppable Mega PC! Yikes!
When I turn my cache off, the sys check is a lot lower. The SLC chip you have has cache so turning it on should almost double your score! (you just need to hunt down the software assumming the cyrix wont work, however Texas made SLC chips for cyrix).There were two types of the texas slc chip (one of them was a TI486SXLC which had 8k cache vs the 1k cache that I have on mine).
Once I install the cf cards then will check score again and see if it improves, after that ......
Talking about spare ISA slots...
Im on the lookout for a SBC on ISA. They are however very expensive but will make my mega pc into 3 different computers/consoles in one unit!
- DOS gaming rig
- Usable Internet Machine
There is a chap in the US that has been new powerleap cards but he wants too much so looking at other sources. The cards is basically a whole computer on an ISA sized card with usb, ethernet, vga, sound and processor. If I install one of these, I can make the a usable everyday computer.
If I cant get one cheap then Im either going to go for either a network card (as I should be able to use it to transfer files from a modern computer to the mega pc)
or use one of these for the slave cf card;
This will allow me to remove the slave CF card externally and copy fies onto it without having to open up the mega pc (which I do often!).
I think the soundcard option doesnt do it for me as the ad lib sound was standard for most software for 386 and early 486's.
Oh forgot to ask, whens the 486 transplant operation scheduled? Cant wait to see the results (either your going to destroy the board or make mega pc history - hopefully the latter!)
Last edited by limboy777; 06-10-2012 at 02:20 PM.
I was looking over my 386SX and 486SLC Mega PC motherboards comparing crystals (I am going to need to change at least one onboard crystal oscillator I suspect to get any additional speed from the CPU). And I found this in my "Web Harvested" images folder.
Compare it with my 386SX motherboard and my 486SLC motherboard. Perhaps my 486SLC motherboard was a lucky hack or possible future revision for the Mega PC that never happened because no one bought it? Either way it is interesting to compare the boards. And it looks like I wont be upgrading any CPUs or crystals for a while yet. I think researching is half the fun of these projects. Learning so much about the past and where everything began.
Edit: This would also indicate that the TX486SLC and the AMD386SX chip are 5V chips. Whereas the TX486SLC/E should be 3.3V - apparently for laptops, embedded and lower power use applications. That gives me hope in the project for replacing the 386SX with the 486SXLC2-G50-PQ CPU should work correctly. At least according to this site here. However that site also says the TX486SLC/E is 5V. Ughhh... I think trial and error suits best. I'll try it, and if it catches fire and burns down my home we'll know I was wrong!
Edit 2: My home will not burn down just yet. The TX486SLC/E used on my 486SLC board is also 5V. Texas Instruments manufactured chips for Cyrix since they were fabless. And I found the site from where I harvested that Mega PC Plus board. Yippee!
Last edited by RetroJunkie; 06-17-2012 at 06:33 AM.
Hi just checking in been really busy at home and work.
Retro - is the pic of a mega pc plus board? - "Edit 2: My home will not burn down just yet. The TX486SLC/E used on my 486SLC board is also 5V. Texas Instruments manufactured chips for Cyrix since they were fabless. And I found the site from where I harvested that Mega PC Plus board. Yippee!"
When you say harvested, have you got another mega pc board? or are you refering to one you already have?
Glad your house is not going to burn down.
Ive tested a 2gb cf card and it works fast. Syscheck shows an improvement as there is no disk access time.
Nemesis - I havent forgotten about the scans but hopefully within 2 weeks I should free.
aha! gotcha limboy777 !!!
You can grab CalmiraXP 4.0b from the following site if you haven't found it yet: http://www.abzone.be/index.php?project=CalmiraXP
Yep that certainly looks like a Mega PC Plus board! I noticed mine had newer date codes on a lot of the chips.
Originally Posted by limboy777
Maybe mine was going to be a revision by never happened because no-one wanted it?
Oh just images I'd grabbed from all over the net in my search for Mega PC motherboard images to see if there were any more boards that might have been compatible.
I also enjoy my house not burning down :-) Especially because I don't want Tom Jones coming over.
No disk access time seems pretty quick haha! Very nice work - don't forget more pictures when you get a chance!
I know what being on the clock is like - and you've got a family to take care of too! Keep it up :-)
Originally Posted by keropi
Welcome to the forum!
For those who dont know keropi from other forums, he knows everything about everything to do with vintage computers (+other stuff!) and a general nice guy as well!
I didnt actively look but will try this version before I try windows 95 (sent you a pm earlier). A fully working version of calmira xp is my first choice so hopefully this version is better than the one I downloaded! Will be a while before I try though!
from the images and from my search ive seen so far it looks like only certain amstrad 486 motherboards seem to fit inside a mega pc case. (the slimline types).
will take pics when everything is finished but it will be a while yet!
The cf card on the slot is my first choice and ive abondoned the sbc idea a while back!
Last edited by limboy777; 06-23-2012 at 06:27 PM.
SBC was cheating anyway! Glad you ditched it!
Originally Posted by limboy777
I sit here in the same room as the Mega PC... Still with no PS/2 keyboard... Even if I had one I'd probably have to hit myself in the face with it for forgetting to bring it so many times. Hopefully tomorrow will change all that.
I don't know where I put those 50MHz CPUs anyway. I am sure they'll turn up when I unpack some of my things. It's difficult trying to narrow down what you are collecting when you have so... many... things! I don't know how but I ended up with three Dreamcast keyboards and an empty box for one.
And the mod is complete, 50MHz was so fast it blew up and melted my LCD panel.
Well at least there's a more definitive end to this particular motherboards life.
It barely survived the NiCad damage and the IDE channel never worked, but now it is truly goneski!
Sorry Limboy... Guess I am not really able to tell you if that VRAM was detected and addressed properly...
I tried sticking the old CPU back on it but there were some delightful blue sparks from the side of the CPU.
Talk about bridged pins Ouch!
Then when I was pulling the socketed chips off the motherboard I stabbed my finger with one of the BIOS chips.
Chalk that up with the soldering iron burn and now we are in business...
Limboy, how has your Mega PC been going as of late?
I guess I should do some more looking into how to speed up my measly 33MHz Mega PC.
The quest never ends!
Last edited by RetroJunkie; 07-21-2012 at 07:27 AM.
Hi so sorry to hear that. Did you film/photograph/document it? is it not salvageable?
Thanks for keeping the thread alive.
One of my mega pc's is on my desk in bits. my main upgraded one just requires me to install my two hdds (one cf card and one 80 ide). I have a load of old dos games on cd ( a few hundred) which I plan to install. (thanks to keropi)
At the moment, Ive got a lot of home and work commitments hence no posts for ages....Ive not really been loggin in as well but just thought I would today!
Once this month is over, hopefully I should have more time and will post with a vengeance.
I got another mega pc (actually its not a full mega pc, just the casing), im planning to use this for modding i.e install a mini itx and megadrive to usb adapter.
Ive got an megadrive emulator with over 800 games which works amazingly well on my laptop so thought I would salvage the mega pc case and house a modern itx pc with megadrive emulator.
finding a cheap mini itx pc/motherboard is hard though!
I will then have the following;
1x upgraded mega pc (486 cyrix one)
2x standard mega pcs (will sell these at some point)
1x modified itx mega pc
Sold a load of my gaming stuff (mainly duplicate amiga or pc stuff).
if nemesis is reading, im really sorry, i will do the scans of my documentation as soon as i can.
Originally Posted by RetroJunkie
Last edited by limboy777; 07-21-2012 at 05:14 PM.
just had a quick check of your site. Im interested in how your upgrade of the megadrive from 68000 / 68010 goes.
What advantage does this upgrade have for the megadrive?
Ive recently ordered a ceramic 68010 for my commodore cdtv in order to upgrade to use whdload. I wonder if this is the same as what you are doing. The cdtv one clips off using a tool. Is the megadrive one soldered on?
Ive also ordered a 8mb upgrade which fits under the 68000 / 68010 on the cdtv however , it needs to be configured with software. There are ram boards that work automatically (auto-configure) so would be interesting to see if anyone has tried this on a megadrive?
Oh yes, forgot to ask...a lot of megadrives have been modified to run at 60hz. Do you know if the mega pc board is modifyable (if thats a word!)?
Last edited by limboy777; 07-21-2012 at 05:37 PM.
Hiya limboy777 !
Adding ram to the megadrive (if even possible) won't give it any advantage with current games... even if it was possible then it would require newly written software to take advantage of it... not much point in it IMHO ;)
Overclocking the md cpu can only help in some games that have slow-downs in demanding situations but even that is not working 100% since it helps said games but breaks others (that's why most ppl doing that oc just a switch to enable/disable it...)
now about that 50/60hz question, IIRC the megadrive board uses the md2 chipset, so you can see the info here and adapt them accordingly, the same principles apply - only the board design is different...
Yes sir! I've got lots of video and final photos of the motherboard before I scrapped it. A sad way for it to go, it was pretty mangled thanks to that NiCad anyway.
Hi there Keropi! I have to say I didn't have much luck with that particular MD2 mod there, I've done my ones through here.
The Mega Drive 1 CPUs are soldered onto the board, I have all the CPUs just no sockets. Why are they taking so long!
The 68010 chips have issues on some games for whatever reason and will not play them all. Whereas the 68000 chip clocked higher with a crystal will give less slow down. Admittedly the only place I ever encountered the slowdown until recently is losing rings in any Sonic game. It's usually those darned dragonfly things with the spiky tails. Dammit!
I really should wrap up my Mega Drive 2 mods this weekend. But where is my motivation? Misplaced with a busted Mega PC motherboard maybe?
I know the TeraDrives run at 60Hz, but yes I would like to see some Mega PCs region / Hz modded. I don't want to do it to mine as I only have one and preservation of the Mega Drive card is of utmost priority. Even if I changed the motherboard to a 486-based one!
I'll have my videos up sometime in the next week though. I'm working on splitting my pictures of the 386 and 486 based Mega PC, even though it is technically the same machine, they are quite different!
That setup in that photos is rather nice looking. I was hoping to do something similar, but then real life got in the way which is just annoying. But we must battle on! For King and Country!