64 megabytes is more than enough image memory for ordinary imaging applications, but EPIX customers are commonly attempting the extraordinary. More memory has been requested. In response, EPIX has developed the 4MEG VIDEO Image Memory Expansion board (4M12-IME) that can provide up to 256 megabytes of image memory!
Occupying an adjacent slot in the PC, 4M12-IME provides the following memory sizes: 4, 8, 12, 16, 32, 48, 64, 128, 192, and 256 megabytes.
In order to span this full range, from 4 to 256 megabytes, accommodating 1, 4, or 16 megabyte SIMMs, EPIX needed to design 3 memory board configurations. The 4M12-IME that accepts 1 megabyte SIMMs provides either 4, 8, 12, or 16 megabytes-each larger memory size requiring 4 more SIMMs. The board that accepts 4 megabyte SIMMS provides 16, 32, 48, or 64 megabytes in the same fashion, while 16 megabyte SIMMs offer 64, 128, 192, or 256 megabytes. AT the present time, when using 16 megabyte SIMMs, because of their larger size, a total of 3 PC slots are occupied instead of the usual 2.
The 4M12-IME is available with either 4, 8, 12, or 16 SIMMs installed. SIMM upgrades are available directly from EPIX, or the user can install non-EPIX SIMMs. 8 bit and 9 bit SIMMs can be mixed since the ninth bit is not used-parity checking is not implemented. Adequate SIMM speed is important. 60 nanoseconds is an absolute minimum. Many applications require faster speeds. The frequency of the slowest SIMM determines 4M12-IME's maximum memory speed, and if too slow, will limit the 4MEG VIDEO's sampling rate. SIMMs supplied by EPIX with the purchase of the board are guaranteed (by EPIX) for 1 year.
Why not DMA?? DMA is an abbreviation for Direct Memory Access, a common means for providing large blocks of memory. The DMA technique stores images directly in the computer's RAM. Several EPIX competitors use this strategy. The advantage of DMA is that standard computer memory is relatively inexpensive. The drawback with DMA is that computer memory is too slow to allow real time image capture at the pixel clock rates supported by EPIX products. The 4MEG VIDEO Model 12, for example, is capable of capturing and displaying 1Kx1K images in excess of 30 frames per second-DMA would preclude this type of capability. As a result, EPIX decided against use of DMA.
The 4MEG VIDEO Model 12 Image Memory Expansion board
is already in production and boards will be available in August.
4MEG VIDEO Model 12 Version 4.3 and later are compatible. 4MIP
V2.9 is required. An upgrade program for earlier boards is available.
Customers who need pixel clock rates faster than 30 MHz must use
one of the single slot memory options already offered. Contact
your distributor, or EPIX, for additional details.
EPIX Vision - July 1994 Newsletter