What shoud I pay for an Atari 400?

[+bob1200xl]

Memory upgrades are not PBI devices, although they use the PBI signal lines. The difference is that there is no code associated with them and no 'address' allocated for them in the OS. The MIO is not a memory upgrade, only a group of PBI devices.

 

The 600XLs that I have seen provide power for the PBI buss. The 800XLs do not. Using an external supply is optional, for the most part.

 

Piggybacking a chip isn't a good idea if it has to dissapate a lot of heat - some do, some do not. You can't plug the larger memory chips (like 1megx8) into a 64K socket because the pin count is different.

 

The internal upgrade plugs into the BASIC ROM socket. You cannot flip the chips onto the bottom of the board and gain much height without spreading them all over the m/b. We could use very low profile chips that solder directly to the upgrade board if it was needed.

 

Using an existing PBI upgrade would be harder than just doing your own, actually. You're modifying a modification that probably doesn't have specs and a schematic. We already know the Atari pretty well.

 

A PBI upgrade is nice because you don't have to do much, if anything, inside your machine. In this case, you would have to get under the covers if you wanted all 512K. (so you could disable BASIC)

 

My vote would be for an internal upgrade.

 

Bob

 

 

Thanks for the heads up MG and bob1200

 

Just a couple of questions though (re the 600)

 

Firstly, assuming that you were doing an internal Ram upgrade and placing a pcb over the empty 600 ram sockets and populating it with whatever memory you were sticking in there…what would be the minimum clearance allowed from the top of the populated pcb to the 600’s shielding…or if you got rid of the shielding (unwise from what I hear) from the populated pcb to the keyboard component

 

My thinking is, is to allow the maximum amount of clearance by using a double sided pcb and making sure that the populated side is facing the motherboard (or is that dangerous)

 

Also I’ve heard that some people when doing 130/65xe memory upgrades (I don’t think it’s relevant to xl’s since their memory is socketed) that they piggyback the ram chips ontop of each other…like homebrew USDoubler style….isn’t there a danger of power surges as the bottom chip will be generating a lot of power/heat etc…of does the power regulation on the xe’s always dissipate which means that each component receives the right amount of power to work (thus preventing power surges/overheating)

 

Wouldn’t a better way to do xe mem. upgrades is just to upgrade the ram chips themselves to say x lots of 16k to x lots of 32k or whatever…that way you avoid having to piggyback chips

 

Also Bob1200 mention a PBI based mem. upgrade…

 

Wouldn’t it be easier to get hold of say a Yorkie (if they were available in the US) or a broken MIO/1064 etc (which were available in the US) and work the memory upgrade around that…that way Bob save a lot of time for parts…as most of the part will be there already and since MG knows about PBI-ECI extenders these upgrades can also work in xe’s as well

 

Yorkie and 1064 if mem recall’s were PBI devices (I think MIO was one too)