An extension to speed up IIsi use without giving slow disk operation.
This extension is for Macintosh IIsi users, running System 7 or greater,
only. The IIsi does not have VRAM, and video circuitry and the CPU must
take turns to access the motherboard-mounted 1Mb that contains the screen
However, this screen image can only be up to around 330K, leaving 700 or
so K for use by applications. Applications loaded into this space will be
very slow, as they can only run when the CPU, and not the video circuitry,
is accessing this bank of RAM.
A standard cure for this is to increase the size of the disk cache to 768K.
This fills the rest of this bank, pushing the applications down into the
other bank. The applications then execute at normal speed. However, a large
disk cache is inefficient, as Apple's disk cacheing is somewhat less than
optimal. And, as the cache only gets accessed by the CPU when the video
is busy elsewhere, you have sped up your applications but slowed your hard
Adding Macsbug means you can reduce the disk cache size to around 384K, but
this is still not ideal. This extension marks the 1Mb not used by Macsbug or
the screen as unused, so the disk cache lives in the other bank, and you can
have a small, fast disk cache again.
(1.7 KiB / 1.74 KB)
IIsi RAM-Muncher INIT / compressed w/ Stuffit
(4.47 KiB / 4.58 KB)
/ BinHex'd, use Stuffit Expander
From Mac OS 7.0
up to Mac OS 7.6
Mac OS 7.x