6128 x2 - Differences?

[crayzyian]

All,

Just came into possession of two 6128s.  Before I start having a poke around (they probably need a clean etc.) I wondered whether anyone could offer advice on the differences based on Version and/or Serial No. - of course there might not be any of significance, but I thought I'd ask the CPCWiki community, out of interest as much as anything else!

Thanks in advance,

Ian

[roudoudou]

if you open them you will see the differences (pay attention when opening of the keyboard web-wires)

gate array + AY should be the same
CRTC may be different
FDC+PLL may be different
and of course, the Drive model!
you can take pictures of them for the cpcwiki page, in case you have something new
https://www.cpcwiki.eu/index.php/Mainboard_Versions

[poulette73]

Hello,

Maybe open them up and take a look at the motherboard serial numbers :

https://www.cpcwiki.eu/index.php/Mainboard_Versions#CPC6128_version_1_.288pin_data_separator.2C_solder_points_for_old_and_new_gate_array.29

[EDIT] Roudoudou you were faster by the time I validated my message... 

[crayzyian]

Thanks both - I suppose my ultimate conundrum is which of the two I should be keeping, which I accept will not simply depend on specification at time of production but also what condition etc. they're in...

[andycadley]

That may depend on what you want to do with them. If it's games and simple applications, there's probably no difference. If you want to try out demos etc, it'll be more likely you'll want to keep the one with the "best" CRTC type. And if you just want a display model, it'll be the one with the shiniest case.

[GUNHED]

The only significant difference to keep in mind is the CRTC. There is software to read the CRTC type. CRTC types 0 and 1 are good. While type 2 will not work with few demos. 

[roudoudou]

The only significant difference to keep in mind is the CRTC. There is software to read the CRTC type. CRTC types 0 and 1 are good. While type 2 will not work with few demos. 

significant difference with drives too, there is at least 2 known games which cannot run with drives after 1987

[McArti0]

out &bcff,12:?inp(&bfff), inp(&beff)

<48        255   crtc 0
 0             0     crtc 1
 0            255  crtc 2
<48         <48  crtc 3,4

[eto]

but also what condition etc. they're in.

Keyboard can also be relevant. There are keyboards where some of the letters get rubbed off. In my personal experience, this primarily happens to newer machines while old ones are perfect even after almost 40 years.

You could also use those parts from each machine which are best. The nicest case, the best keyboard, the best drive...

[GUNHED]

The only significant difference to keep in mind is the CRTC. There is software to read the CRTC type. CRTC types 0 and 1 are good. While type 2 will not work with few demos. 

significant difference with drives too, there is at least 2 known games which cannot run with drives after 1987

Ha! But the major difference regarding drives is between CPC and Plus. While the CPC drives go to "Ready" status after writing just in time, there is a problem with the Plus drives: Sometimes (about 30% of the cases) after writing a track / sector the drives switches to "Ready" just a bit to early. Now if you do issue a SEEK command directly afterwards the internal track register of the FDC contains a wrong value! This bug was tedious to find!!!