Newbie - Dewoo CPC-400s. Memory prevents running MSX software

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By KURILSHIK

Supporter (6)

Аватар пользователя KURILSHIK

26-09-2015, 05:40

Ups. Delete as double. Sorry.

By KURILSHIK

Supporter (6)

Аватар пользователя KURILSHIK

26-09-2015, 06:12

NYYRIKKI wrote:
KURILSHIK wrote:
NYYRIKKI wrote:

Maybe someone can now help you hardware vice (?) I think, that you just need to cut few foils, solder few jumper wires and change new ROM. After that you have an extremely good MSX2.

Sorry for nekroposting.
I also have Dewoo CPC-400. I have the ability to cut and solder tracks on the board. What I need change in my Daewoo ?

I've newer seen such a machine and also I can't find service manual, so this is a bit tough one to help with... How ever from MSX engine Wiki I found that this machine should have S1985 on board...

I would start by tracing the lines from that chip... The pin 53 should be going back of the machine and pin 45 should be going towards RAM... If that is correct, I would start by cutting these wires and jumpwire foild going to pin 45 to go to pin 53 instead... That should already improve software compatibility a LOT. This will anyway disable the expansion bus from the back, but is it used to anything anyway or is it just for "future purposes" as I expect?

If you have to courage, then please test and report back the results.

(BTW S1985 manual is here)

Thank you.
Well, I'll try as soon as myself will understand with the circuitry. And be sure to let you know the results.
But I'm new to MSX. And I can not to do everything quickly.

Anyway, I can send any photos of inside my Daewoo.
Yet, I have a some extra machine Daewoo. If you wish I would can presented (If you not against to pay shipping). But I do not know how much is mail service. I not have a experience.

By NYYRIKKI

Enlighted (5918)

Аватар пользователя NYYRIKKI

26-09-2015, 16:20

I found one picture of the upper side of the motherboard. From the picture it looks like that if there is S1985, it must be on bottom side of the PCB. This is MSX specific chip and I agree the slot handling is not very easy to understand. How ever browsing the forum posts here will help. I think from hardware point of view these things were last time discussed here.

If you have an extra Daewoo CPC-400s I might be interested in buying it from you, if the price is good. I could then do the testing my self and send you back detailed instructions with pictures. If this sound like a good plan, please make me an offer. My email is in my profile. In exchange I could also help you to upgrade it to MSX2+ if you wish. (Sending out ready written EPROMs & new VDP) From the pictures I saw that the important chips are in sockets, so this should be pretty much just dropping in new chips with few bend legs & jump wires.

By RetroTechie

Paragon (1563)

Аватар пользователя RetroTechie

26-09-2015, 18:00

KURILSHIK wrote:

I also have Dewoo CPC-400.

CPC-400 or CPC-400S ? AFAIK these machines should be very similar, apart from that the -S has superimpose function built in. But I've only ever seen CPC-400S inside, so I can't say for sure. Either model is probably very rare outside Korea or Russia.

NYYRIKKI wrote:

How ever from MSX engine Wiki I found that this machine should have S1985 on board...

(link needed) Anyway that info is not correct I think.

Like said, I've had the CPC-400S on my workbench once, and took extensive notes. Dunno if I still have those notes though, or if so where... Sad But IIRC, I can say this:

* Based on DW64MX1 engine IC, info on my very own site here. Same as used in some other Korean (Zemmix) machines. For one, this explains the unusual memory layout. Possibly even a PAL or GAL somewhere to control ROM select signals etc. Shouldn't be too difficult to move ROMs around between slots as they are present. But to change the slot layout itself (for example change expanded slot 0 into expanded slot 3) would basically involve building a copy of the slot select logic. Only a little bit easier than building an MSX2 from scratch... LOL!
* Had some ancient floppy controller on board, WD1770 / 1772 or something. And a diskROM with it that had -by default- some more bytes free in BASIC, but also very, very, very slow. The latter not a hardware problem though - see below.
* Clearly very customized towards Korean market: some special screen mode a la Kanji, but then for entering Han characters. Machine should have some CALL commands (_HANON, _HANOFF, _ADJUST ?) for this too.
* Reminded me of Philips 8250/55/80 machines. A bit older components but (physically) built much better. Very nice keyboard too.
* 2 EPROMs of 64KB each, named U38 and U44. Put together an updated version of U38 for that machine, which made it more "international" / compatible and included a much faster diskROM. If desired, I can upload those ROMs somewhere.

By mars2000you

Enlighted (6227)

Аватар пользователя mars2000you

26-09-2015, 18:08

RetroTechie wrote:

* Clearly very customized towards Korean market: some special screen mode a la Kanji, but then for entering Han characters. Machine should have some CALL commands (_HANON, _HANOFF, _ADJUST ?) for this too.

See

- the wiki about Hangul BASIC : http://www.msx.org/wiki/Hangul_BASIC

- this thread about Hanja characters : http://www.msx.org/forum/msx-talk/general-discussion/how-use...

By NYYRIKKI

Enlighted (5918)

Аватар пользователя NYYRIKKI

26-09-2015, 19:45

RetroTechie wrote:

(link needed) Anyway that info is not correct I think.

I picked the info from here.

Quote:

* Based on DW64MX1 engine IC, info on my very own site here. Same as used in some other Korean (Zemmix) machines. For one, this explains the unusual memory layout. Possibly even a PAL or GAL somewhere to control ROM select signals etc. Shouldn't be too difficult to move ROMs around between slots as they are present. But to change the slot layout itself (for example change expanded slot 0 into expanded slot 3) would basically involve building a copy of the slot select logic. Only a little bit easier than building an MSX2 from scratch... LOL!

Oh, this is totally unknown chip for me! Daewoo custom MSX-engine !??

From what I read from your page it looks like RAM is hardcoded internally to slot 0-2... That is bad... That is very, very bad... Why on earth they did that!? Even SVI (that i've been working most with) had their own custom chip, but they had RAMSEL-pin that you could connect to any slot select pin.... This version looks pretty much locked to unfixable state unless you add your own memorymapper to expansion slot... But that is not easy / little project anymore. As long as the RAM is in slot 0 there is going to be a lot of headaches and cursing for users.

By mars2000you

Enlighted (6227)

Аватар пользователя mars2000you

26-09-2015, 20:06

On this Russian site, there's a (? frozen) project to replace DW64MX1 : http://sblive.narod.ru/MSX/CPC-300E/CPC-300E.htm

By NYYRIKKI

Enlighted (5918)

Аватар пользователя NYYRIKKI

26-09-2015, 22:04

Ok, now RetroTechie or someone with better knowledge should say something... I'm trying to learn a bit more about HW... Would this be a working workaround for the RAM slot problem? (= Would this be a working memory mapper?)

Buy HM628512BLP-7, piggy pack it with some ROM and connect DW64MX1 lines like this:
MA14 -> A14
MA15 -> A15
MA16 -> A16
MA17 -> A17
GND -> A18
/WR -> /WE
/SLT3 -> /OE
/MREQ -> /CE

???

By maxis

Champion (512)

Аватар пользователя maxis

26-09-2015, 23:12

@RetroTechie
1. CPC400S - full blown GENLOCK and all mode DIGITIZER built-in. Digitizer only supports NTSC 3.579545 subcarrier. Actually brilliant machine.
2. CPC400 and CPC400S motherboards are identical. The exception is MC1377P video encoder board on the CPC400 vs SONY V7010/20/30/40 digitizer chipset on the CPC400S.
3. WD1770 actually integrates the fully digital PLL data separator unlike WD2793 and doesn't require the thermal compensation. So this is the last generation of DD floppy controller, which is fast enough to read HD disks (HW patch is required).
4. Ultra fast motherboard.
5. Keyboard is closely compatible with Yamaha YIS805 (very few changes to be done).

@NYYRIKKI
Having a memory in the expanded slot 0 doesn't violate the MSX standard, right? Does it impose any problem on the legacy SW?

BTW, what is really horrible is Yamaha CX11, where you have the standard 32K (8000-FFFE) in the non-expanded slot 0 (atop of the BIOS) and the lower 32K of RAM is in unexpanded slot 3 to get the full 64 KB of memory.

@Mars2000you I was totally unaware of the WEB site you have mentioned. Had a wrong impression that all the CPC300/CPC400 work was gradually stopped around 1999 in Russia. Found the ASIC replacement project quite an interesting attempt. The guy uses Altera MAX7128. I was using back in 1996 Intel FLEXLOGIC IFX780 as the ASIC replacement.

@KURILSHIK You can remove the RAS signal from the built-in memories and hook-up the 256 RAM extension to the slot connector on the BACK of the machine (actually this is 100mil double row 50pin connector, like single-ended SCSI).

By RetroTechie

Paragon (1563)

Аватар пользователя RetroTechie

27-09-2015, 00:33

NYYRIKKI wrote:

I picked the info from here.

Guess I should re-write (the English version of) that page one of these days... LOL! Say, with a nice table showing which feature(s) is included in which MSX engine IC.

Quote:

Oh, this is totally unknown chip for me! Daewoo custom MSX-engine !??

Yes, probably. But essentially it includes 8255, slot select / DRAM control / 256K mapper, and some glue logic (VDP chip select, printer, ...), not even a PSG. So it is not a very complex chip internally. 64 pin shrink DIP (same housing as V9938/58).

Quote:

From what I read from your page it looks like RAM is hardcoded internally to slot 0-2... That is bad... That is very, very bad... Why on earth they did that!?

Slot 1, 2 and 3 unexpanded and free/available? Not great compatibility-wise, but a nice start for heavily customized MSXes.

NYYRIKKI wrote:

Buy HM628512BLP-7, piggy pack it with some ROM and connect DW64MX1 lines like this:
MA14 -> A14
MA15 -> A15
MA16 -> A16
MA17 -> A17
GND -> A18
/WR -> /WE
/SLT3 -> /OE
/MREQ -> /CE

???

I'd try:
Some /SLTSL -> /CE
/RD -> /OE
/WR -> /WE

But yes, expanding to a 256KB mapper (in slot 0-2!) should be fairly easy. For >256KB, look at full-blown mapper connected to cartridge or expansion slot.

maxis wrote:

Having a memory in the expanded slot 0 doesn't violate the MSX standard, right? Does it impose any problem on the legacy SW?

No, it's perfectly fine according to MSX standard. But a LOT of existing software will have trouble with this config. For example I'd expect the 'universal' POKE -1 to hang this machine (since all pages already set to primary slot 0, so this poke would instantaneous switch 64K RAM into all pages - under BASIC :o ).

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