DKTronics RAM Expansion on a Plus.

[Bryce]

Hi All,
      on the DKTronics RAM Expansion page it claims that they will only work on non-plus CPCs. I tried both a 64K and a 256K version on my 6128+ last night and they both work fine. I also can't find any technical reason why they wouldn't work. Is there some known problem that I haven't encountered yet, or is this just some random claim that was never fully investigated.

Bryce.

[Badstarr]

I don't know very much about the technical stuff concerning the RAM expansions but I do remember that my DkTronics 464 RAM expansion apparently enabled the extra BASIC functions that the 464 did not have, perhaps they were concerned this would lead to some incompatibilities? I no longer have my 64k RAM expansion to test, it got lost in some house moving expedition unfortunately.


The only other reasons I can think of is that, as you know, the plus and classic cpc connectors were different so they claimed incompatibility based on that so that people did not buy it and find it could not be connected. Or they wanted to cash in on a host of new upgrades with the launch of the plus range by releasing the same unit in plus clothing. I think the latter makes more sense as I can remember reading in AA that you could buy something called a 'widget' which if I remember correctly, adapted the edge connector hardware to run on the centronics style port.


I think this probably happens a lot, as a Mac owner I often find that HW companies release identical products for Mac and PC but charge more for the Mac version when the only difference is the colour of the product or the driver cd!

[Bryce]

The additional commands could only have been stored in a ROM, which the 64K RAM expansion doesn't have. Are you sure it wasn't a 64K Silicon disk you owned? That has a ROM, but I wasn't aware of anything other than the RAMDisk commands being stored there.

The interface connection is of course different, but I have built an adapter to use my DK stuff on German and Plus machines This one: http://www.cpcwiki.eu/index.php/Expansion_Converter

It was just the statement on the Wiki page that made me curious, because if the person thought that it was only the connector that was a problem, then they would/should have also listed the German CPCs as incompatible.

Bryce.

[Badstarr]

I hope it wasn't a 64k Silicone Disk as I will be more depressed by the thought of losing it ! I'm pretty sure it was the 64k DkTronics RAM expansion as I remember it was on the label. I got it with my 464 around 1998 when my 6128 had a faulty drive and the expansion came with it as well as a DDI-1. I remember the expansion unit I had was often advertised on the back page of AA, infact I have a copy in front of me right now. And... it appears that the extra commands were delivered in the software, so no ROM, however, I'm sure I had access to extra basic commands like |FRAME etc with the unit attached?


This bit of info may interest you more though! Under the advertising blurb it says the following..." 464+ NEEDS ADAPTOR (£9.99)" I will attach an image...

[Bryce]

Ok, but the extra commands were to manipulate the extra RAM, not the additional commands that BASIC 1.1 offers.

The silicon disk and the RAM expansion are almost identical from a hardware point of view (except for the ROM bit), but that is available in the Wiki and can be installed on any ROMBoard if you need it. The only other hardware difference is that the RAM version maps the RAM to Bank 0 to 3, whereas the Silicon disk maps it to Banks 4 to 7. But this can also be easily changed with just a single link on the PCB. So if you own one, it's easy to convert it to the other. Or if you have two 256K expansions you can plug both in (one as RAM, one as SiliconDisk) and you get 512K RAM (576K total, including the 64K in the CPC)

I'll be putting together a tutorial soon about upgrading and converting DK RAM expansions, and it will all be explained there.

Bryce.

[ZilogMonkey]

Hi Bryce!

I don't think it's the connector that is the cause for the incompatibility statement...

I really depends on the way the ASIC of the plus is addressed. I think when a DK'tronics bank is switched in the from say #4000 - #8000, it will always be the top layer of ram with priority over the ASIC ram #6000 onwards!

Eg..

case A:
On a CPC6128 plus. When the ASIC is enabled and the the first 16kb bank is switched in (OUT #7F, #c4). The ASIC ram is visible(addressable) from #6000 onwards. 

case B:

On a CPC464 plus with 64Kb DK'tronics compatible memory expansion (Should be equal to a CPC6128 plus).  When the ASIC is enabled and the the first 16kb bank is switched in (OUT #7F, #c4). The ASIC ram is not visible from #6000 onwards (The expansion takes precedence)

---

So clearly the CPC plus is not workable with a DK'tronics memory expansion unless the PLUS features are addressed with memory banks switched of!.. It's a bit tricky though it depends on what a DK'tronics memory expansion is supposed to be, clearly the CPC plus came after DK'tronics memory expansions!

DK'tronics expansions are clearly usable with a plus, but there should be taken some special considerations when programming it together with the plus features! Sorry for my crap english!

/ZilogMonkey

[Bryce]

Your English is fine, and that was a very good description. I wasn't aware of that "feature". Could someone make some sort of small test program to check if this really does occur as suspected?

Thanks,
Bryce.

[TFM]

Hi All,
      on the DKTronics RAM Expansion page it claims that they will only work on non-plus CPCs. I tried both a 64K and a 256K version on my 6128+ last night and they both work fine. I also can't find any technical reason why they wouldn't work. Is there some known problem that I haven't encountered yet, or is this just some random claim that was never fully investigated.

Bryce.

They may talk about their software ? Which would not make much more sense ?!?

[TFM]

I really depends on the way the ASIC of the plus is addressed. I think when a DK'tronics bank is switched in the from say #4000 - #8000, it will always be the top layer of ram with priority over the ASIC ram #6000 onwards!

No, external RAM has higher priority than internal RAM, but the ASIC has always the highest priority.

The ASIC also uses 16 KB full! It does not bank in at &6000!

The ASIC is usually switched off, except the program needs to access the memory mapped I/O. During this time no RAM can be accessed between &4000-&7FFF. So what? It doesn't matter.

The external RAM expansions for the 6128 are fully compatible to the Plus. All of them.
(Problems will arise with ROM banking though, see SF2 on Plus).

[Bryce]

Write me a test program and I can let you know for sure with a real test.

Bryce.

[TFM]

Write me a test program and I can let you know for sure with a real test.

Bryce.

Not needed, I do know that. A lot of my programs are living proof :-)

EDIT: Use OUT commands in BASIC and POKE / PEEK to check :-)

[MacDeath]

I tried both a 64K and a 256K version on my 6128+ last night

I believed a +64k extra RAM put on a cpc6128 would actually do nothing more than what a 6128 normally have : 128K...

Is it different on a 6128PLUS ?

Or is it a special +64K expansion designed to "work" on a 6128... turning it into a 6192 ?

[Bryce]

Nothing special, they are both standard DKtronics expansions, made for the original CPC. One is 64K (so useless at the moment for a 6128), the other is 256K. I was wondering because the Inicron RAM expansion claims to work fine on the Plus, but the DKTronics doesn't. So do these incompatibilites that TFM mentions also effect the Inicron expansion, or do these incompatibilites only happen in particular RAM Configs that the Inicron doesn't support?

Bryce.

[TFM]

I believed a +64k extra RAM put on a cpc6128 would actually do nothing more than what a 6128 normally have : 128K...

Right. 64K expansions are for 464 or 664. No gain on the 6128.

Is it different on a 6128PLUS ?

No.

Or is it a special +64K expansion designed to "work" on a 6128... turning it into a 6192 ?

No.

[TFM]

Nothing special, they are both standard DKtronics expansions, made for the original CPC. One is 64K (so useless at the moment for a 6128), the other is 256K. I was wondering because the Inicron RAM expansion claims to work fine on the Plus, but the DKTronics doesn't. So do these incompatibilites that TFM mentions also effect the Inicron expansion, or do these incompatibilites only happen in particular RAM Configs that the Inicron doesn't support?

Bryce.

Well, I don't mention RAM incompatibilities between 6128 oG or Plus. I only assume, if there are incompatibilities, then they are cause by software.

I did run succesfully Dobbertin, dk'tronics, Inicron and Symbiface2 RAM expansions on the CPC6128 and 6128Plus - there are no differences, neither from the hardware side nor low level access.

So don't care about Plus or not.

Plus-problems will arise with ROM banking (maybe, in seldom cases), but not with RAM.

Have a good day!