Couple of points brought up in that Excelerator XL 20 information.
Two 256k SIMMs required on the MoBo, position dependent upon SE Revision. WAG: the SE's frame buffer a/o memory used during boot was moved from one physical bank to the other in revision?
Max. memory config is 8MB, which means that it's 24bit only. Makes sense as this would be of a 2nd or 3rd generation of SE accelerators, dunno where to make the divisions. Connectix released Virtual in 1989 and MODE32 in 1991. Compact Virtual would have released at some point after those, being something of a combination of both by my read.***** High capacity "Silicon Disk" Virtual Memory hacks for addressing additional RAM in the last generation of SE Accelerators lay a couple of years into the future when this Accelerator was current.
IOW, you can probably forget about addressing anything more than 8MB on your accelerator, minus whatever Frame Buffer memory space remains hardwired to the SE's Video Subsystem on the MoBo in those two slots.
***** As trag mentioned, the memory addressing scheme of Accelerators would be based on any given card's ROM, not Apple's flawed Color ROMs. So, dunno how the Dirty ROM fiasco might have affected Accelerators for the SE? Was the SE FDHD ROM based on subset of the Mac II ROM or a patch made on the SE ROM? Curious.
Two 256k SIMMs required on the MoBo, position dependent upon SE Revision. WAG: the SE's frame buffer a/o memory used during boot was moved from one physical bank to the other in revision?
Max. memory config is 8MB, which means that it's 24bit only. Makes sense as this would be of a 2nd or 3rd generation of SE accelerators, dunno where to make the divisions. Connectix released Virtual in 1989 and MODE32 in 1991. Compact Virtual would have released at some point after those, being something of a combination of both by my read.***** High capacity "Silicon Disk" Virtual Memory hacks for addressing additional RAM in the last generation of SE Accelerators lay a couple of years into the future when this Accelerator was current.
IOW, you can probably forget about addressing anything more than 8MB on your accelerator, minus whatever Frame Buffer memory space remains hardwired to the SE's Video Subsystem on the MoBo in those two slots.
***** As trag mentioned, the memory addressing scheme of Accelerators would be based on any given card's ROM, not Apple's flawed Color ROMs. So, dunno how the Dirty ROM fiasco might have affected Accelerators for the SE? Was the SE FDHD ROM based on subset of the Mac II ROM or a patch made on the SE ROM? Curious.