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From: davidb@braa.inmos.co.uk (David Boreham)
Newsgroups: comp.arch
Subject: Re: fast DRAMs and caches
Message-ID: <1977@ganymede.inmos.co.uk>
Date: 2 Sep 89 18:01:00 GMT
References: <1989Aug30.185926.1410@mentor.com>
Sender: news@inmos.co.uk
Reply-To: davidb@braa.UUCP (David Boreham)
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Mabe this will help the discussion about RAM types and speeds:

Known "best" RAMs of various kinds, devices which are available
commercially but may not yet be in volume prodn

SRAM-   about 10ns at 64K, 20ns at 256K. Cycle time = access time.
        Generally no latched address or data.

CMOS DRAM- about 60ns access, 120ns cycle at 1Mbit. 80ns access,
        160ns cycle at 4Mbit. (page mode and static column about 30ns cycle).

CMOS VRAM- Lags about 6--12 months behind normal DRAM in performance.
          Currently 100ns access, 190ns cycle. Serial port about 25MHz.
          Can expect to speed up to DRAM speeds in the next year.

BiCMOS DRAM- 35ns access, 70ns cycle. Very expensive. Non-multiplexed
          address. No static-column. 

As for the devices persented at ICCSD and other conferences (like
the 16ns DRAM mentioned awhile back), these device will not become
generally available for quite some time. (Usually conference paper
devices are at least 2 years away from production).

David Boreham, INMOS Limited | mail(uk): davidb@inmos.co.uk or ukc!inmos!davidb
Bristol,  England            |      (us): uunet!inmos-c!davidb
+44 454 616616 ex 543        | Internet : @col.hp.com:davidb@inmos-c