RamFAST revision D
By Drew
Copyright (c) 1992 Apple Users' Group, Sydney
Republished from Applecations, a publication of the Apple Users' Group, Sydney, Australia.
CV Technologies
CV Technologies is now shipping the revision D RamFAST-SCSI.
The rev D has four major improvements over the rev C board.
1. It's smaller, we've reduced the size from 10"x3" to 5"x3".
2. It consumes less power, rev C pulled 0.7 amps, the rev D pulls 0.15 amps.
3. The rev D board can DMA into non-DMA compatible memory products.
4. The rev D has expandable cache, 256k or a 1meg.
The revision D RamFAST board uses surface mount CMOS chips to dramatically reduce the power consumption and the size of the board. We have also developed a new DMA circuit that can DMA above the 4 meg limit and it can DMA into memory products that are not normally DMA compatible, such as a RamKeeper with 2 cards or a RamPak-4GS. This new DMA circuit uses a new technique to handle memory products that violate the Apple Technotes on bank latching. If the memory product uses bank latching then it would normally be non-DMA compatible due the fact that the bank latch contains an invalid value when DMA occurs. The new DMA circuit puts a valid value into the memory product's bank latch before doing DMA.
This new technique will allow DMA to every memory card that I have encountered. The only bump in the road is the Transwarp GS. The Transwarp GS was not designed in strict accordance with the processor that it replaces and one of the discrepancies prohibits the new DMA circuit from putting valid bank latch data into the memory expansion product. Therefore if you have a TWGS you will not be able to DMA above 4 meg nor will you be able to DMA into non-DMA compatible memory products. The Zip-GS does not have this design defect nor does the processor that comes in the motherboard. I have also developed a replacement DMA control pal for the rev C board that will allow a rev C board to use this new technique. If you are interested then contact CV Technologies.
We have also changed the memory circuit such that it uses 256kx4 drams instead of the 256kx1 chips we used to use. We can also expand the memory on board from 256k to 1 meg. The memory expansion is user installable and will be available directly from CV Tech. A 256k rev C board will have the same performance characteristics of a 256k rev D board. Bumping the cache size to a meg improves the performance a fair amount depending on the application. I can reboot Gs/OS completely from cache in under 4 seconds using a 1meg rev D board. One other visible performance boost is that you cannot fill the cache with writes on a 1meg board because the board will write the data to the disk fast enough to keep some of the 1meg free for additional writes.
Due to the low current ratings of the CMOS chips we do not suggest that customers that are using a rev C RamFAST in a IIe upgrade to the rev D.
The bus loading that is typical in a loaded IIe may be too "heavy" for the CMOS parts on the rev D board. Bus loading is not a problem in the GS due to the segregated bus architecture of the GS.
List price for the rev D board 256k is US$199.00
List price for the rev D board 1meg is US$279.00
Upgrade cost from rev C to rev D (256k) US$ 69.00
Upgrade cost from rev C to rev D (1meg) US$139.00

THIS CONTENT COPYRIGHT © 2007, APPLE MACINTOSH USERS' GROUP, SYDNEY
Permission has been obtained to make this material available on the Internet.

Permission is hereby granted for non-profit user groups to republish this content.
PLEASE CREDIT THE AUTHOR AND THE SOURCE: Applecations, publication of the Apple Users' Group, Sydney, Australia

THIS PAGE COPYRIGHT © 2007, ANDREW ROUGHAN