A500 memory related questions

[cpfuture]

Hi,

I recently bought an A500+ for next to nothing, which I plan to use as my new main A500. I bought an A500+ because of the possibility of having more Chip RAM available than the usual 512K. I also bought a CSA Mega Midget Racer accelerator with an 030 CPU at 25MHz and 8MB of memory which I plan to install. I have an M-Tec AT-500 IDE controller which I plan to stick into the side slot of this A500+. This IDE controller will use a CF card for that totally silent computing I love.  :-D The M-Tec has an added 4MB of RAM.

I want to max out this A500+ in such a way that it can be both pimped out with as much memory as I can fit into it, but still be able to run 1.3 Kickstart games originally from floppy. Now, I have Googled around for a couple of hours for old Usenet postings and I think I have it sorted out, but I'd just like to confirm with some of you here. Below are some of my assumptions. I hope some of you can either confirm or deny them. Here we go:

The A500 could only address a maximum of 8MB of Fast RAM due to the 24-bit addressing space of the 68000 as it is implemented in the A500.

The A500+ can have a maximum of 2MB of Chip RAM.

The Chip RAM comes on top of the 8MB Fast RAM, so the total amount of memory that can be addressed by an A500+ with a 68000 CPU is 10MB.

The CSA Mega Midget Racer has a daughterboard with 8MB Fast RAM. This RAM falls outside of the afforementioned 8MB autoconfig memory, because it is addressed by the 68030 which has 32-bit addressing capability.

The M-Tec AT500 IDE controller that goes in the side expansion slot of the A500(+) has 4MB onboard autoconfig memory. So if I connect that to the A500+ and install the CSA Mega Midget Racer I will have 1MB Chip RAM + 4MB Fast RAM (from the M-Tec AT500) + 8MB Fast RAM (from the CSA Mega Midget Racer) which is a total of 13MB.

I can add another 1MB of Chip RAM to the A500+ using its trap door to increase this to 14MB.

Actually, the M-Tec AT500 is populated with 30-pin SIMMS up to a maximum of 8MB. Currently it has 4MB in 2 SIMMs. If I added another 4MB I'd have the M-Tec AT500 populated with the maximum of 8MB. So theoretically I could have 2MB Chip RAM + 8MB M-Tec AT500 Fast RAM and 8MB of 32-bit RAM on the CSA Mega Midget Racer and have a total of 18MB.

A lot of assumptions.... I just hope most of them are true. The cool thing about the CSA accelerator and the M-Tec IDE controller is that both can be disabled. Also, the M-Tec has room for a Kickstart ROM and a switch on its front panel so I can switch between a native Kickstart 1.3 and 2.04 ROM. I could play classic A500 games which need the 1.3 ROM and have a pimped out 18MB A500 with a 68030 CPU ath 25MHz all at the same time.

[Damion]

cpfuture wrote:
Hi,

I recently bought an A500+ for next to nothing, which I plan to use as my new main A500. I bought an A500+ because of the possibility of having more Chip RAM available than the usual 512K. I also bought a CSA Mega Midget Racer accelerator with an 030 CPU at 25MHz and 8MB of memory which I plan to install. I have an M-Tec AT-500 IDE controller which I plan to stick into the side slot of this A500+. This IDE controller will use a CF card for that totally silent computing I love.  :-D The M-Tec has an added 4MB of RAM.

I want to max out this A500+ in such a way that it can be both pimped out with as much memory as I can fit into it, but still be able to run 1.3 Kickstart games originally from floppy. Now, I have Googled around for a couple of hours for old Usenet postings and I think I have it sorted out, but I'd just like to confirm with some of you here. Below are some of my assumptions. I hope some of you can either confirm or deny them. Here we go:

The A500 could only address a maximum of 8MB of Fast RAM due to the 24-bit addressing space of the 68000 as it is implemented in the A500.

Pretty much. Actually, there is a maximum addressable of 16 megs, 7 are considered "reserved" IIRC.

The A500+ can have a maximum of 2MB of Chip RAM.

The Chip RAM comes on top of the 8MB Fast RAM, so the total amount of memory that can be addressed by an A500+ with a 68000 CPU is 10MB.

Chipram doesn't come on top of the 8 mb per se, they are both included in the 16 meg total.

The CSA Mega Midget Racer has a daughterboard with 8MB Fast RAM. This RAM falls outside of the afforementioned 8MB autoconfig memory, because it is addressed by the 68030 which has 32-bit addressing capability.

The M-Tec AT500 IDE controller that goes in the side expansion slot of the A500(+) has 4MB onboard autoconfig memory. So if I connect that to the A500+ and install the CSA Mega Midget Racer I will have 1MB Chip RAM + 4MB Fast RAM (from the M-Tec AT500) + 8MB Fast RAM (from the CSA Mega Midget Racer) which is a total of 13MB.

I can add another 1MB of Chip RAM to the A500+ using its trap door to increase this to 14MB.

Actually, the M-Tec AT500 is populated with 30-pin SIMMS up to a maximum of 8MB. Currently it has 4MB in 2 SIMMs. If I added another 4MB I'd have the M-Tec AT500 populated with the maximum of 8MB. So theoretically I could have 2MB Chip RAM + 8MB M-Tec AT500 Fast RAM and 8MB of 32-bit RAM on the CSA Mega Midget Racer and have a total of 18MB.

A lot of assumptions.... I just hope most of them are true. The cool thing about the CSA accelerator and the M-Tec IDE controller is that both can be disabled. Also, the M-Tec has room for a Kickstart ROM and a switch on its front panel so I can switch between a native Kickstart 1.3 and 2.04 ROM. I could play classic A500 games which need the 1.3 ROM and have a pimped out 18MB A500 with a 68030 CPU ath 25MHz all at the same time.

Sounds like you've got it figured out, hopefully it will work like that. (Although, I'm not so sure about the M-Tec playing nice with the Midget Racer, as far as the ram is concerned at least. RAM in the M-Tec *may* slow things down a little, if it's still a 16-bit data path to the Midget Racer. Someone with a little more knowledge may be able to elaborate.)

--edit-- The Racer may use that same "auto config" space like the A530 seems to, in which case I'm thinking it won't work. I dunno how accelerators like the Viper get around that, as I'm no hardware expert...

[cpfuture]

Thanks for your input, -D-! I have a couple of other IDE controllers that slip into the side slot lying around, but the M-Tec would be nice, because of the easy way to switch between two Kickstart ROMs. Otherwise I'd have to fit a ROM switch inside the A500. The Mega Midget Racer including daughterboard isn't really that 'midget-y' compared to other accelerators, so I'm not sure whether there's enough room for both.

[alexh]

Just remember to remove the internal battery from the A500+ before it leaks.

[cpfuture]

alexh wrote:
Just remember to remove the internal battery from the A500+ before it leaks.

Thanks for the tip. I forgot the A500+ had a battery as standard.