Easiest way to upgrade 464 plus to 128Kb internal RAM?

[AxelStone]

Hi everyone, I'm seeing that there is a lot of homebrew games that uses 128kb, so I've decided to upgrade internally my CPC 464 plus. The only upgrade I'm interested is extra 64Kb RAM internal, since I don't need fdd (C4CPC and M4 are perfect to load sofwtare).


Can someone link the easiest tutorial to make that? Thanks! 

[||C|-|E||]

You can follow the excellent tutorial that Bryce prepared and focus only on the RAM part:

http://www.cpcwiki.eu/index.php/464Plus_Conversion

I also did a conversion and created a thread with lots of pictures not so long ago. Maybe it will be useful 

http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/my-464-fixes-and-conversion/

For the RAM you will need a couple of sockets, two caps, a pair of resistors and, of course, the ICs (R28, R55, C12, C13, IC12 and IC13 in Bryce´s tutorial)  Oh! and a lot of braid!

[AxelStone]

Thanks man, I had just reading it. I found this other one (https://cpcrulez.fr/hardware_montage_8x-cpc_464_plus-memory_upgrade_AA.htm) that is practically equals but uses one extra component, C99. According to Bryce tutorial, it seems it's don't needed. As I can see in your thread you soldered sockets to the mainboard instead of chips directly, I suposse to avoid damage RAM chips, maybe?

I'll follow your suggestion, thanks!

[||C|-|E||]

If you solder sockets and, later, a socketed IC fails, it is very easy to replace it. Otherwise, you would need to de-solder the IC again, heating the board and the rest of the components during the process and potentially damaging something else. If you can, try to use sockets for all your ICs 

[Bryce]

Thanks man, I had just reading it. I found this other one (https://cpcrulez.fr/hardware_montage_8x-cpc_464_plus-memory_upgrade_AA.htm) that is practically equals but uses one extra component, C99. According to Bryce tutorial, it seems it's don't needed. As I can see in your thread you soldered sockets to the mainboard instead of chips directly, I suposse to avoid damage RAM chips, maybe?

I'll follow your suggestion, thanks!

C99 would give additional stability to the 5V rail, but I've no idea why the guy on cpcrulez thinks it's necessary, Amstrad certainly didn't think it was required because it's not present on the 6128+.

Bryce.

[Syncmaster319]

Hi All,


I'm thinking about having a go at the RAM upgrade for my 464 plus.


Would anybody be able to sense check the parts here to make sure I have the right stuff (minus the RAM chips)


Thanks
Mark

[||C|-|E||]

Oh! nope, those resistors are surface mount ones. You need something like this and, if possible, rated 1/8W.



If you have troubles finding them, I can tell you an E-bay seller that has what you need in stock  (otherwise, just look for 1/8W resistors on E-bay and choose the correct value).

P.D: I think that you are ordering two tubes of 26 sockets each! 

[Syncmaster319]

Oh! nope, those resistors are surface mount ones. You need something like this and, if possible, rated 1/8W.



If you have troubles finding them, I can tell you an E-bay seller that has what you need in stock  (otherwise, just look for 1/8W resistors on E-bay and choose the correct value).

P.D: I think that you are ordering two tubes of 26 sockets each! 

Thanks!


If you could point me in the right direction for any of the components that would be really appreciated


Mark

[||C|-|E||]

For example, this guy sells them

http://www.ebay.co.uk/itm/100-x-1-8W-5-Carbon-film-Resistors-Select-from-Range-10-ohm-to-1M-ohm-value-/162326839033?var=&hash=item25cb6efef9:m:mGgKbeX4rx8rbG1H6TTlC5g

[AxelStone]

Is there any way to buy all components to the same seller? In order to save shipping cost :-)

[||C|-|E||]

Huuum... to be honest I bought them from different sources. You can always try a big big supplier, like RS components.

[AxelStone]

C99 would give additional stability to the 5V rail, but I've no idea why the guy on cpcrulez thinks it's necessary, Amstrad certainly didn't think it was required because it's not present on the 6128+.

Bryce.

Yeah but it seems that the way he enables extra 64k is different. In CPC wiki schemas it seems that solder 2 black wires to 2 componets in the board. However according to french schemas, he solder a RAM chip to 2 point above it.

I mean, 464+ board has 2 black wires soldered to nothing, in your modification I see that you add C21 and C23 to the end of the. Are they needed to get 128Kb enabled?

Thanks.

[Bryce]

Nope, there's only one way to enable the extra 64K. The black wires have nothing to do with the extra RAM nor do the caps at the end of those wires. The black wires are there because someone at Amstrad messed up the PCB layout and caused a long ground loop. This causes the voltages at the FDC to be wrong (offset). To fix this the two black wires were added to give the ground path a shortcut. The two capacitors at the end of the black wires are part of the FDC circuit and have nothing to do with the RAM.
The black wires on the 464+ are not going to nothing, they are connecting two points along the ground path.

Bryce.

[AxelStone]

Nope, there's only one way to enable the extra 64K. The black wires have nothing to do with the extra RAM nor do the caps at the end of those wires. The black wires are there because someone at Amstrad messed up the PCB layout and caused a long ground loop. This causes the voltages at the FDC to be wrong (offset). To fix this the two black wires were added to give the ground path a shortcut. The two capacitors at the end of the black wires are part of the FDC circuit and have nothing to do with the RAM.
The black wires on the 464+ are not going to nothing, they are connecting two points along the ground path.

Bryce.

Thanks man, this weekend I'm opening my 464+ 

[AxelStone]

Upgraded to 128Kb! I'm a happy man now 

[Bryce]

Congratulations.

With or without the extra capacitor?

Bryce.

[AxelStone]

Without, the basic modification and works fine.

[Bryce]

Good. I still don't know how the French site came to the idea that it was needed. Maybe they had a really noisy power supply?

Anyway, enjoy all the 128K games.

Bryce.